Subject: Re: bug#57556: 28.1; Eshell not finding executables in PATH when tramp-integration loaded

From: Jim Porter <[email-masked]>
Date: Sun, 16 Oct 2022 16:07:42 -0700

On 10/16/2022 1:51 PM, Richard Stallman wrote:
> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
> 
>    > My intent was to make that display as all-caps in the HTML documentation
>    > as well. In that excerpt, 'NAME' should always be an environment
>    > variable, so I used the capitalization conventions that env vars usually
>    > use. 'name', on the other hand, could be a Lisp variable or an env var.
> 
> It should be @var{name} to express that it is a metasyntactic variable
> that stands for something called ``name''.

Thanks. I've fixed my changes in the Eshell manual to use this 
convention now, and also added some further cross-references.

I've attached (hopefully) the final version of these patches, which I'll 
merge in the next day or so, unless someone finds any other issues.

From 046d15f14fcdf5816072c5dcb844f9dd4882051c Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Wed, 12 Oct 2022 11:28:05 -0700
Subject: [PATCH 1/7] ; Remove over-quoting of :application values in
 connection-local variables

* test/lisp/files-x-tests.el (files-x-test--application)
(files-x-test--another-application):
* doc/lispref/variables.texi (Connection Local Variables): Remove
extra quotes.
---
 doc/lispref/variables.texi | 14 +++++++-------
 test/lisp/files-x-tests.el |  4 ++--
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/doc/lispref/variables.texi b/doc/lispref/variables.texi
index 1d891618da..2a06169b21 100644
--- a/doc/lispref/variables.texi
+++ b/doc/lispref/variables.texi
@@ -2311,13 +2311,13 @@ Connection Local Variables
 @example
 @group
 (connection-local-set-profiles
-  '(:application 'tramp :protocol "ssh" :machine "localhost")
+  '(:application tramp :protocol "ssh" :machine "localhost")
   'remote-bash 'remote-null-device)
 @end group
 
 @group
 (connection-local-set-profiles
-  '(:application 'tramp :protocol "sudo"
+  '(:application tramp :protocol "sudo"
     :user "root" :machine "localhost")
   'remote-ksh 'remote-null-device)
 @end group
@@ -2329,13 +2329,13 @@ Connection Local Variables
 @example
 @group
 (connection-local-set-profiles
-  '(:application 'tramp :protocol "ssh" :machine "localhost")
+  '(:application tramp :protocol "ssh" :machine "localhost")
   'remote-bash)
 @end group
 
 @group
 (connection-local-set-profiles
-  '(:application 'tramp :protocol "sudo"
+  '(:application tramp :protocol "sudo"
     :user "root" :machine "localhost")
   'remote-ksh)
 @end group
@@ -2365,7 +2365,7 @@ Connection Local Variables
 @example
 @group
 (hack-connection-local-variables
-  '(:application 'tramp :protocol "ssh" :machine "localhost"))
+  '(:application tramp :protocol "ssh" :machine "localhost"))
 @end group
 
 @group
@@ -2401,7 +2401,7 @@ Connection Local Variables
 
 @group
 (connection-local-set-profiles
-  '(:application 'tramp :protocol "ssh" :machine "remotehost")
+  '(:application tramp :protocol "ssh" :machine "remotehost")
   'remote-perl)
 @end group
 
@@ -2429,7 +2429,7 @@ Connection Local Variables
 
 @group
 (connection-local-set-profiles
-  '(:application 'my-app :protocol "ssh" :machine "remotehost")
+  '(:application my-app :protocol "ssh" :machine "remotehost")
   'my-remote-perl)
 @end group
 
diff --git a/test/lisp/files-x-tests.el b/test/lisp/files-x-tests.el
index 7ee2f0c1a6..2f6d0d4a99 100644
--- a/test/lisp/files-x-tests.el
+++ b/test/lisp/files-x-tests.el
@@ -42,9 +42,9 @@ remote-null-device
 (put 'remote-shell-login-switch 'safe-local-variable #'identity)
 (put 'remote-null-device 'safe-local-variable #'identity)
 
-(defconst files-x-test--application '(:application 'my-application))
+(defconst files-x-test--application '(:application my-application))
 (defconst files-x-test--another-application
-  '(:application 'another-application))
+  '(:application another-application))
 (defconst files-x-test--protocol '(:protocol "my-protocol"))
 (defconst files-x-test--user '(:user "my-user"))
 (defconst files-x-test--machine '(:machine "my-machine"))
-- 
2.25.1

From 28c5a764fe9b1042ee2af64f710a4c4fdedcae43 Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Tue, 11 Oct 2022 22:11:04 -0700
Subject: [PATCH 2/7] Add helpers to dynamically assign connection-local values

* lisp/files-x.el (connection-local-criteria)
(connection-local-profile-name-for-setq): New variables.
(with-connection-local-variables-1): ... let-bind them here.
(connection-local-update-profile-variables)
(connection-local-profile-name-for-criteria): New functions.
(with-connection-local-application-variables, setq-connection-local):
New macros.

* test/lisp/files-x-tests.el: Require 'tramp-integration'
(files-x-test--variable5, remote-lazy-var): New variables.
(files-x-test-hack-connection-local-variables-apply): Expand checks.
(files-x-test-with-connection-local-variables): Remove
'hack-connection-local-variables-apply' check (it belongs in the above
test), and expand some other checks.
(files-x-test--get-lazy-var, files-x-test--set-lazy-var): New
functions.
(files-x-test-connection-local-update-profile-variables)
(files-x-test-setq-connection-local): New tests.

* doc/lispref/variables.texi (Connection Local Variables): Split into
two subsections and document the new features.

* etc/NEWS: Announce 'setq-connection-local'.
---
 doc/lispref/variables.texi |  98 ++++++++++++++++++------
 etc/NEWS                   |   7 ++
 lisp/files-x.el            | 103 ++++++++++++++++++++++++--
 test/lisp/files-x-tests.el | 148 +++++++++++++++++++++++++++----------
 4 files changed, 288 insertions(+), 68 deletions(-)

diff --git a/doc/lispref/variables.texi b/doc/lispref/variables.texi
index 2a06169b21..cbe276b2dc 100644
--- a/doc/lispref/variables.texi
+++ b/doc/lispref/variables.texi
@@ -2239,9 +2239,26 @@ Connection Local Variables
 @cindex connection local variables
 
   Connection-local variables provide a general mechanism for different
-variable settings in buffers with a remote connection.  They are bound
+variable settings in buffers with a remote connection (@pxref{Remote
+Files,, Remote Files, emacs, The GNU Emacs Manual}).  They are bound
 and set depending on the remote connection a buffer is dedicated to.
 
+@menu
+* Connection Local Profiles::            Storing variable settings to
+                                         apply to connections.
+* Applying Connection Local Variables::  Using connection-local values
+                                         in your code.
+@end menu
+
+@node Connection Local Profiles
+@subsection Connection Local Profiles
+@cindex connection local profiles
+
+  Emacs uses connection-local profiles to store the variable settings
+to apply to particular connections.  You can then associate these with
+remote connections by defining the criteria when they should apply,
+using @code{connection-local-set-profiles}.
+
 @defun connection-local-set-profile-variables profile variables
 This function defines a set of variable settings for the connection
 @var{profile}, which is a symbol.  You can later assign the connection
@@ -2356,6 +2373,14 @@ Connection Local Variables
 list.
 @end deffn
 
+@node Applying Connection Local Variables
+@subsection Applying Connection Local Variables
+@cindex connection local variables, applying
+
+  When writing connection-aware code, you'll need to collect, and
+possibly apply, any connection-local variables.  There are several
+ways to do this, as described below.
+
 @defun hack-connection-local-variables criteria
 This function collects applicable connection-local variables
 associated with @var{criteria} in
@@ -2384,9 +2409,9 @@ Connection Local Variables
 @var{criteria}, and immediately applies them in the current buffer.
 @end defun
 
-@defmac with-connection-local-variables &rest body
-All connection-local variables, which are specified by
-@code{default-directory}, are applied.
+@defmac with-connection-local-application-variables application &rest body
+Apply all connection-local variables for @code{application}, which are
+specified by @code{default-directory}.
 
 After that, @var{body} is executed, and the connection-local variables
 are unwound.  Example:
@@ -2394,20 +2419,20 @@ Connection Local Variables
 @example
 @group
 (connection-local-set-profile-variables
-  'remote-perl
-  '((perl-command-name . "/usr/local/bin/perl")
+  'my-remote-perl
+  '((perl-command-name . "/usr/local/bin/perl5")
     (perl-command-switch . "-e %s")))
 @end group
 
 @group
 (connection-local-set-profiles
-  '(:application tramp :protocol "ssh" :machine "remotehost")
-  'remote-perl)
+  '(:application my-app :protocol "ssh" :machine "remotehost")
+  'my-remote-perl)
 @end group
 
 @group
 (let ((default-directory "/ssh:remotehost:/working/dir/"))
-  (with-connection-local-variables
+  (with-connection-local-application-variables 'my-app
     do something useful))
 @end group
 @end example
@@ -2416,30 +2441,59 @@ Connection Local Variables
 @defvar connection-local-default-application
 The default application, a symbol, to be applied in
 @code{with-connection-local-variables}.  It defaults to @code{tramp},
-but in case you want to overwrite Tramp's settings temporarily, you
-could let-bind it like
+but you can let-bind it to change the application temporarily
+(@pxref{Local Variables}).
+
+This variable must not be changed globally.
+@end defvar
+
+@defmac with-connection-local-variables &rest body
+This is equivalent to
+@code{with-connection-local-application-variables}, but uses
+@code{connection-local-default-application} for the application.
+@end defmac
+
+@defmac setq-connection-local [symbol form]@dots{}
+This macro sets each @var{symbol} connection-locally to the result of
+evaluating the corresponding @var{form}, using the connection-local
+profile specified in @code{connection-local-profile-name-for-setq}; if
+the profile name is @code{nil}, this macro will just set the variables
+normally, as with @code{setq} (@pxref{Setting Variables}).
+
+For example, you can use this macro in combination with
+@code{with-connection-local-variables} or
+@code{with-connection-local-application-variables} to lazily
+initialize connection-local settings:
 
 @example
 @group
+(defvar my-app-variable nil)
+
 (connection-local-set-profile-variables
-  'my-remote-perl
-  '((perl-command-name . "/usr/local/bin/perl5")
-    (perl-command-switch . "-e %s")))
-@end group
+ 'my-app-connection-default-profile
+ '((my-app-variable . nil)))
 
-@group
 (connection-local-set-profiles
-  '(:application my-app :protocol "ssh" :machine "remotehost")
-  'my-remote-perl)
+ '(:application my-app)
+ 'my-app-connection-default-profile)
 @end group
 
 @group
-(let ((default-directory "/ssh:remotehost:/working/dir/")
-      (connection-local-default-application 'my-app))
-  (with-connection-local-variables
-    do something useful))
+(defun my-app-get-variable ()
+  (with-connection-local-application-variables 'my-app
+    (or my-app-variable
+        (setq-connection-local my-app-variable
+                               do something useful))))
 @end group
 @end example
+@end defmac
+
+@defvar connection-local-profile-name-for-setq
+The connection-local profile name, a symbol, to use when setting
+variables via @code{setq-connection-local}.  This is let-bound in the
+body of @code{with-connection-local-variables}, but you can also
+let-bind it yourself if you'd like to set variables on a different
+profile.
 
 This variable must not be changed globally.
 @end defvar
diff --git a/etc/NEWS b/etc/NEWS
index 9641587052..72b2331b81 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -3214,6 +3214,13 @@ TIMEOUT is the idle time after which to deactivate the transient map.
 The default timeout value can be defined by the new variable
 'set-transient-map-timeout'.
 
++++
+** New macro 'setq-connection-local'.
+This allows dynamically setting variable values for a particular
+connection within the body of 'with-connection-local-variables'.  See
+the "(elisp) Connection Local Variables" node in the Lisp Reference
+manual for more information.
+
 +++
 ** 'plist-get', 'plist-put' and 'plist-member' are no longer limited to 'eq'.
 These function now take an optional comparison predicate argument.
diff --git a/lisp/files-x.el b/lisp/files-x.el
index f6d5d6cc27..1ae6586e70 100644
--- a/lisp/files-x.el
+++ b/lisp/files-x.el
@@ -618,6 +618,18 @@ connection-local-criteria-alist
   :group 'tramp
   :version "29.1")
 
+(defvar connection-local-criteria nil
+  "The current connection-local criteria, or nil.
+This is set while executing the body of
+`with-connection-local-variables'.")
+
+(defvar connection-local-profile-name-for-setq nil
+  "The current connection-local profile name, or nil.
+This is the name of the profile to use when setting variables via
+`setq-connection-local'.  Its value is derived from
+`connection-local-criteria' and is set while executing the body
+of `with-connection-local-variables'.")
+
 (defsubst connection-local-normalize-criteria (criteria)
   "Normalize plist CRITERIA according to properties.
 Return a reordered plist."
@@ -694,6 +706,23 @@ connection-local-set-profile-variables
   (customize-set-variable
    'connection-local-profile-alist connection-local-profile-alist))
 
+;;;###autoload
+(defun connection-local-update-profile-variables (profile variables)
+  "Update the variable settings for PROFILE in-place.
+VARIABLES is a list that declares connection-local variables for
+the connection profile.  An element in VARIABLES is an alist
+whose elements are of the form (VAR . VALUE).
+
+Unlike `connection-local-set-profile-variables' (which see), this
+function preserves the values of any existing variable
+definitions that aren't listed in VARIABLES."
+  (when-let ((existing-variables
+              (nreverse (connection-local-get-profile-variables profile))))
+    (dolist (var variables)
+      (setf (alist-get (car var) existing-variables) (cdr var)))
+    (setq variables (nreverse existing-variables)))
+  (connection-local-set-profile-variables profile variables))
+
 (defun hack-connection-local-variables (criteria)
   "Read connection-local variables according to CRITERIA.
 Store the connection-local variables in buffer local
@@ -736,6 +765,15 @@ connection-local-criteria-for-default-directory
       :user        ,(file-remote-p default-directory 'user)
       :machine     ,(file-remote-p default-directory 'host))))
 
+(defun connection-local-profile-name-for-criteria (criteria)
+  "Get a connection-local profile name based on CRITERIA."
+  (when criteria
+    (let (print-level print-length)
+      (intern (concat
+               "autogenerated-connection-local-profile/"
+               (prin1-to-string
+                (connection-local-normalize-criteria criteria)))))))
+
 ;;;###autoload
 (defmacro with-connection-local-variables (&rest body)
   "Apply connection-local variables according to `default-directory'.
@@ -743,16 +781,28 @@ with-connection-local-variables
   (declare (debug t))
   `(with-connection-local-variables-1 (lambda () ,@body)))
 
+;;;###autoload
+(defmacro with-connection-local-application-variables (application &rest body)
+  "Apply connection-local variables for APPLICATION in `default-directory'.
+Execute BODY, and unwind connection-local variables."
+  (declare (debug t) (indent 1))
+  `(let ((connection-local-default-application ,application))
+     (with-connection-local-variables-1 (lambda () ,@body))))
+
 ;;;###autoload
 (defun with-connection-local-variables-1 (body-fun)
   "Apply connection-local variables according to `default-directory'.
 Call BODY-FUN with no args, and then unwind connection-local variables."
   (if (file-remote-p default-directory)
-      (let ((enable-connection-local-variables t)
-            (old-buffer-local-variables (buffer-local-variables))
-	    connection-local-variables-alist)
-	(hack-connection-local-variables-apply
-	 (connection-local-criteria-for-default-directory))
+      (let* ((enable-connection-local-variables t)
+             (connection-local-criteria
+              (connection-local-criteria-for-default-directory))
+             (connection-local-profile-name-for-setq
+              (connection-local-profile-name-for-criteria
+               connection-local-criteria))
+             (old-buffer-local-variables (buffer-local-variables))
+	     connection-local-variables-alist)
+	(hack-connection-local-variables-apply connection-local-criteria)
 	(unwind-protect
             (funcall body-fun)
 	  ;; Cleanup.
@@ -764,6 +814,49 @@ with-connection-local-variables-1
     ;; No connection-local variables to apply.
     (funcall body-fun)))
 
+;;;###autoload
+(defmacro setq-connection-local (&rest pairs)
+  "Set each VARIABLE connection-locally to VALUE.
+
+When `connection-local-profile-name-for-setq' is set, assign each
+variable's value on that connection profile, and set that profile
+for `connection-local-criteria'.  You can use this in combination
+with `with-connection-local-variables', as in
+
+  (with-connection-local-variables
+    (setq-connection-local VARIABLE VALUE))
+
+If there's no connection-local profile to use, just set the
+variables normally, as with `setq'.
+
+The variables are literal symbols and should not be quoted.  The
+second VALUE is not computed until after the first VARIABLE is
+set, and so on; each VALUE can use the new value of variables set
+earlier in the `setq-connection-local'.  The return value of the
+`setq-connection-local' form is the value of the last VALUE.
+
+\(fn [VARIABLE VALUE]...)"
+  (declare (debug setq))
+  (unless (zerop (mod (length pairs) 2))
+    (error "PAIRS must have an even number of variable/value members"))
+  (let ((set-expr nil)
+        (profile-vars nil))
+    (while pairs
+      (unless (symbolp (car pairs))
+        (error "Attempting to set a non-symbol: %s" (car pairs)))
+      (push `(set ',(car pairs) ,(cadr pairs)) set-expr)
+      (push `(cons ',(car pairs) ,(car pairs)) profile-vars)
+      (setq pairs (cddr pairs)))
+    `(prog1
+         ,(macroexp-progn (nreverse set-expr))
+       (when connection-local-profile-name-for-setq
+         (connection-local-update-profile-variables
+          connection-local-profile-name-for-setq
+          (list ,@(nreverse profile-vars)))
+         (connection-local-set-profiles
+          connection-local-criteria
+          connection-local-profile-name-for-setq)))))
+
 ;;;###autoload
 (defun path-separator ()
   "The connection-local value of `path-separator'."
diff --git a/test/lisp/files-x-tests.el b/test/lisp/files-x-tests.el
index 2f6d0d4a99..b1555a0266 100644
--- a/test/lisp/files-x-tests.el
+++ b/test/lisp/files-x-tests.el
@@ -23,6 +23,7 @@
 
 (require 'ert)
 (require 'files-x)
+(require 'tramp-integration)
 
 (defconst files-x-test--variables1
   '((remote-shell-file-name . "/bin/bash")
@@ -35,7 +36,11 @@ files-x-test--variables3
   '((remote-null-device . "/dev/null")))
 (defconst files-x-test--variables4
   '((remote-null-device . "null")))
+(defconst files-x-test--variables5
+  '((remote-lazy-var . nil)
+    (remote-null-device . "/dev/null")))
 (defvar remote-null-device)
+(defvar remote-lazy-var nil)
 (put 'remote-shell-file-name 'safe-local-variable #'identity)
 (put 'remote-shell-command-switch 'safe-local-variable #'identity)
 (put 'remote-shell-interactive-switch 'safe-local-variable #'identity)
@@ -91,6 +96,28 @@ files-x-test-connection-local-set-profile-variables
       (connection-local-get-profile-variables 'remote-nullfile)
       files-x-test--variables4))))
 
+(ert-deftest files-x-test-connection-local-update-profile-variables ()
+  "Test updating connection-local profile variables."
+
+  ;; Declare (PROFILE VARIABLES) objects.
+  (let (connection-local-profile-alist connection-local-criteria-alist)
+    (connection-local-set-profile-variables
+     'remote-bash (copy-alist files-x-test--variables1))
+    (should
+     (equal
+      (connection-local-get-profile-variables 'remote-bash)
+      files-x-test--variables1))
+
+    ;; Updating overwrites only the values specified in this call, but
+    ;; retains all the other values from previous calls.
+    (connection-local-update-profile-variables
+     'remote-bash files-x-test--variables2)
+    (should
+     (equal
+      (connection-local-get-profile-variables 'remote-bash)
+      (cons (car files-x-test--variables2)
+            (cdr files-x-test--variables1))))))
+
 (ert-deftest files-x-test-connection-local-set-profiles ()
   "Test setting connection-local profiles."
 
@@ -233,9 +260,12 @@ files-x-test-hack-connection-local-variables-apply
                  (nreverse (copy-tree files-x-test--variables2)))))
         ;; The variables exist also as local variables.
         (should (local-variable-p 'remote-shell-file-name))
+        (should (local-variable-p 'remote-null-device))
         ;; The proper variable value is set.
         (should
-         (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))))
+         (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))
+        (should
+         (string-equal (symbol-value 'remote-null-device) "/dev/null"))))
 
     ;; The third test case.  Both criteria `files-x-test--criteria1'
     ;; and `files-x-test--criteria2' apply, but there are no double
@@ -274,13 +304,11 @@ files-x-test-hack-connection-local-variables-apply
         (should-not (local-variable-p 'remote-shell-file-name))
         (should-not (boundp 'remote-shell-file-name))))))
 
-(defvar tramp-connection-local-default-shell-variables)
-(defvar tramp-connection-local-default-system-variables)
-
 (ert-deftest files-x-test-with-connection-local-variables ()
   "Test setting connection-local variables."
 
-  (let (connection-local-profile-alist connection-local-criteria-alist)
+  (let ((connection-local-profile-alist connection-local-profile-alist)
+        (connection-local-criteria-alist connection-local-criteria-alist))
     (connection-local-set-profile-variables
      'remote-bash files-x-test--variables1)
     (connection-local-set-profile-variables
@@ -291,29 +319,6 @@ files-x-test-with-connection-local-variables
     (connection-local-set-profiles
      nil 'remote-ksh 'remote-nullfile)
 
-    (with-temp-buffer
-      (let ((enable-connection-local-variables t))
-        (hack-connection-local-variables-apply nil)
-
-	;; All connection-local variables are set.  They apply in
-        ;; reverse order in `connection-local-variables-alist'.
-        (should
-         (equal connection-local-variables-alist
-		(append
-		 (nreverse (copy-tree files-x-test--variables3))
-		 (nreverse (copy-tree files-x-test--variables2)))))
-        ;; The variables exist also as local variables.
-        (should (local-variable-p 'remote-shell-file-name))
-        (should (local-variable-p 'remote-null-device))
-        ;; The proper variable values are set.
-        (should
-         (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))
-        (should
-         (string-equal (symbol-value 'remote-null-device) "/dev/null"))
-
-	;; A candidate connection-local variable is not bound yet.
-        (should-not (local-variable-p 'remote-shell-command-switch))))
-
     (with-temp-buffer
       ;; Use the macro.  We need a remote `default-directory'.
       (let ((enable-connection-local-variables t)
@@ -331,18 +336,18 @@ files-x-test-with-connection-local-variables
 	(with-connection-local-variables
 	 ;; All connection-local variables are set.  They apply in
 	 ;; reverse order in `connection-local-variables-alist'.
-	 ;; Since we ha a remote default directory, Tramp's settings
+	 ;; Since we have a remote default directory, Tramp's settings
 	 ;; are appended as well.
          (should
           (equal
            connection-local-variables-alist
 	   (append
-	    (nreverse (copy-tree files-x-test--variables3))
-	    (nreverse (copy-tree files-x-test--variables2))
             (nreverse
              (copy-tree tramp-connection-local-default-shell-variables))
             (nreverse
-             (copy-tree tramp-connection-local-default-system-variables)))))
+             (copy-tree tramp-connection-local-default-system-variables))
+	    (nreverse (copy-tree files-x-test--variables3))
+	    (nreverse (copy-tree files-x-test--variables2)))))
          ;; The variables exist also as local variables.
          (should (local-variable-p 'remote-shell-file-name))
          (should (local-variable-p 'remote-null-device))
@@ -352,15 +357,21 @@ files-x-test-with-connection-local-variables
          (should
           (string-equal (symbol-value 'remote-null-device) "/dev/null"))
 
-         ;; Run another instance of `with-connection-local-variables'
-         ;; with a different application.
-         (let ((connection-local-default-application (cadr files-x-test--application)))
-	   (with-connection-local-variables
-            ;; The proper variable values are set.
-            (should
-             (string-equal (symbol-value 'remote-shell-file-name) "/bin/bash"))
-            (should
-             (string-equal (symbol-value 'remote-null-device) "/dev/null"))))
+         ;; Run `with-connection-local-application-variables' to use a
+         ;; different application.
+	 (with-connection-local-application-variables
+             (cadr files-x-test--application)
+         (should
+          (equal
+           connection-local-variables-alist
+	   (append
+	    (nreverse (copy-tree files-x-test--variables3))
+	    (nreverse (copy-tree files-x-test--variables1)))))
+           ;; The proper variable values are set.
+           (should
+            (string-equal (symbol-value 'remote-shell-file-name) "/bin/bash"))
+           (should
+            (string-equal (symbol-value 'remote-null-device) "/dev/null")))
          ;; The variable values are reset.
          (should
           (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))
@@ -376,5 +387,60 @@ files-x-test-with-connection-local-variables
 	(should-not (boundp 'remote-shell-file-name))
 	(should (string-equal (symbol-value 'remote-null-device) "null"))))))
 
+(defun files-x-test--get-lazy-var ()
+  "Get the connection-local value of `remote-lazy-var'.
+If it's not initialized yet, initialize it."
+  (with-connection-local-application-variables
+      (cadr files-x-test--application)
+    (or remote-lazy-var
+        (setq-connection-local remote-lazy-var
+                               (or (file-remote-p default-directory 'host)
+                                   "local")))))
+
+(defun files-x-test--set-lazy-var (value)
+  "Set the connection-local value of `remote-lazy-var'"
+  (with-connection-local-application-variables
+      (cadr files-x-test--application)
+    (setq-connection-local remote-lazy-var value)))
+
+(ert-deftest files-x-test-setq-connection-local ()
+  "Test dynamically setting connection local variables."
+  (let (connection-local-profile-alist connection-local-criteria-alist)
+    (connection-local-set-profile-variables
+     'remote-lazy files-x-test--variables5)
+    (connection-local-set-profiles
+     files-x-test--application
+     'remote-lazy)
+
+    ;; Test the initial local value.
+    (should (equal (files-x-test--get-lazy-var) "local"))
+
+    ;; Set the local value and make sure it retains the value we set.
+    (should (equal (files-x-test--set-lazy-var "here") "here"))
+    (should (equal (files-x-test--get-lazy-var) "here"))
+
+    (let ((default-directory "/method:host:"))
+      ;; Test the initial remote value.
+      (should (equal (files-x-test--get-lazy-var) "host"))
+
+      ;; Set the remote value and make sure it retains the value we set.
+      (should (equal (files-x-test--set-lazy-var "there") "there"))
+      (should (equal (files-x-test--get-lazy-var) "there"))
+      ;; Set another connection-local variable.
+      (with-connection-local-application-variables
+          (cadr files-x-test--application)
+        (setq-connection-local remote-null-device "null")))
+
+    ;; Make sure we get the local value we set above.
+    (should (equal (files-x-test--get-lazy-var) "here"))
+    (should-not (boundp 'remote-null-device))
+
+    ;; Make sure we get the remote values we set above.
+    (let ((default-directory "/method:host:"))
+      (should (equal (files-x-test--get-lazy-var) "there"))
+      (with-connection-local-application-variables
+          (cadr files-x-test--application)
+        (should (equal remote-null-device "null"))))))
+
 (provide 'files-x-tests)
 ;;; files-x-tests.el ends here
-- 
2.25.1

From e0224cb5c9277b7059e546a3b93fb52ad7b183d2 Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Sat, 24 Sep 2022 18:13:03 -0700
Subject: [PATCH 3/7] ; Allow ignoring errors when calling
 'eshell-match-command-output'

* test/lisp/eshell/eshell-tests-helpers.el
(eshell-match-command-output): New argument IGNORE-ERRORS.

* test/lisp/eshell/esh-var-tests.el
(esh-var-test/last-status-var-lisp-command)
(esh-var-test/last-status-var-lisp-form)
(esh-var-test/last-status-var-lisp-form-2): Ignore errors when calling
'eshell-match-command-output'.
---
 test/lisp/eshell/esh-var-tests.el        | 15 ++++++---------
 test/lisp/eshell/eshell-tests-helpers.el | 13 ++++++++++---
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/test/lisp/eshell/esh-var-tests.el b/test/lisp/eshell/esh-var-tests.el
index cb5b1766bb..ad695e45d7 100644
--- a/test/lisp/eshell/esh-var-tests.el
+++ b/test/lisp/eshell/esh-var-tests.el
@@ -472,9 +472,8 @@ esh-var-test/last-status-var-lisp-command
                                 "t\n0\n")
    (eshell-match-command-output "zerop 1; echo $?"
                                 "0\n")
-   (let ((debug-on-error nil))
-     (eshell-match-command-output "zerop foo; echo $?"
-                                  "1\n"))))
+   (eshell-match-command-output "zerop foo; echo $?"
+                                "1\n" nil t)))
 
 (ert-deftest esh-var-test/last-status-var-lisp-form ()
   "Test using the \"last exit status\" ($?) variable with a Lisp form"
@@ -484,9 +483,8 @@ esh-var-test/last-status-var-lisp-form
                                   "t\n0\n")
      (eshell-match-command-output "(zerop 1); echo $?"
                                   "2\n")
-     (let ((debug-on-error nil))
-       (eshell-match-command-output "(zerop \"foo\"); echo $?"
-                                    "1\n")))))
+     (eshell-match-command-output "(zerop \"foo\"); echo $?"
+                                  "1\n" nil t))))
 
 (ert-deftest esh-var-test/last-status-var-lisp-form-2 ()
   "Test using the \"last exit status\" ($?) variable with a Lisp form.
@@ -497,9 +495,8 @@ esh-var-test/last-status-var-lisp-form-2
                                   "0\n")
      (eshell-match-command-output "(zerop 0); echo $?"
                                   "0\n")
-     (let ((debug-on-error nil))
-       (eshell-match-command-output "(zerop \"foo\"); echo $?"
-                                    "1\n")))))
+     (eshell-match-command-output "(zerop \"foo\"); echo $?"
+                                  "1\n" nil t))))
 
 (ert-deftest esh-var-test/last-status-var-ext-cmd ()
   "Test using the \"last exit status\" ($?) variable with an external command"
diff --git a/test/lisp/eshell/eshell-tests-helpers.el b/test/lisp/eshell/eshell-tests-helpers.el
index 73abfcbb55..e713e162ad 100644
--- a/test/lisp/eshell/eshell-tests-helpers.el
+++ b/test/lisp/eshell/eshell-tests-helpers.el
@@ -100,9 +100,16 @@ eshell-match-output--explainer
 
 (put 'eshell-match-output 'ert-explainer #'eshell-match-output--explainer)
 
-(defun eshell-match-command-output (command regexp &optional func)
-  "Insert a COMMAND at the end of the buffer and match the output with REGEXP."
-  (eshell-insert-command command func)
+(defun eshell-match-command-output (command regexp &optional func
+                                            ignore-errors)
+  "Insert a COMMAND at the end of the buffer and match the output with REGEXP.
+FUNC is the function to call after inserting the text (see
+`eshell-insert-command').
+
+If IGNORE-ERRORS is non-nil, ignore any errors signaled when
+inserting the command."
+  (let ((debug-on-error (and (not ignore-errors) debug-on-error)))
+    (eshell-insert-command command func))
   (eshell-wait-for-subprocess)
   (should (eshell-match-output regexp)))
 
-- 
2.25.1

From fbf9191ad694c9995a3985175d8b277392400757 Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Wed, 28 Sep 2022 09:34:38 -0700
Subject: [PATCH 4/7] ; Obsolete 'eshell/define'

* lisp/eshell/esh-var.el (eshell/define): Make obsolete, and explain
its current state.

* doc/misc/eshell.texi (Built-ins): Remove 'define'.
---
 doc/misc/eshell.texi   | 5 -----
 lisp/eshell/esh-var.el | 5 +++++
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/doc/misc/eshell.texi b/doc/misc/eshell.texi
index 0ee33f2c2a..8036bbd83a 100644
--- a/doc/misc/eshell.texi
+++ b/doc/misc/eshell.texi
@@ -439,11 +439,6 @@ Built-ins
 is similar to, but slightly different from, the GNU Coreutils
 @command{date} command.
 
-@item define
-@cmindex define
-Define a variable alias.
-@xref{Variable Aliases, , , elisp, The Emacs Lisp Reference Manual}.
-
 @item diff
 @cmindex diff
 Compare files using Emacs's internal @code{diff} (not to be confused
diff --git a/lisp/eshell/esh-var.el b/lisp/eshell/esh-var.el
index 36e59cd5a4..3c09fc52fb 100644
--- a/lisp/eshell/esh-var.el
+++ b/lisp/eshell/esh-var.el
@@ -302,6 +302,11 @@ eshell-interpolate-variable
 
 (defun eshell/define (var-alias definition)
   "Define a VAR-ALIAS using DEFINITION."
+  ;; FIXME: This function doesn't work (it produces variable aliases
+  ;; in a form not recognized by other parts of the code), and likely
+  ;; hasn't worked since before its introduction into Emacs.  It
+  ;; should either be removed or fixed up.
+  (declare (obsolete nil "29.1"))
   (if (not definition)
       (setq eshell-variable-aliases-list
 	    (delq (assoc var-alias eshell-variable-aliases-list)
-- 
2.25.1

From f535cc568bac5d8a90b030547aa1761f6378db9f Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Sun, 25 Sep 2022 21:47:26 -0700
Subject: [PATCH 5/7] Allow setting the values of variable aliases in Eshell

This makes commands like "COLUMNS=40 some-command" work as expected.

* lisp/eshell/esh-cmd.el (eshell-subcommand-bindings): Remove
'process-environment' from here...

* lisp/eshell/esh-var.el (eshell-var-initialize): ... and add to here,
along with 'eshell-variable-aliases-list'.
(eshell-inside-emacs): Convert to a 'defvar-local' to make it settable
in a particular Eshell buffer.
(eshell-variable-aliases-list): Make $?, $$, and $* read-only and
update docstring.
(eshell-set-variable): New function...
(eshell-handle-local-variables, eshell/export, eshell/unset): ... use
it.
(eshell/set, pcomplete/eshell-mode/set): New functions.
(eshell-get-variable): Get the variable alias's getter function when
appropriate and use a safer method for checking function arity.

* test/lisp/eshell/esh-var-tests.el (esh-var-test/set/env-var)
(esh-var-test/set/symbol, esh-var-test/unset/env-var)
(esh-var-test/unset/symbol, esh-var-test/setq, esh-var-test/export)
(esh-var-test/local-variables, esh-var-test/alias/function)
(esh-var-test/alias/function-pair, esh-var-test/alias/string)
(esh-var-test/alias/string/prefer-lisp, esh-var-test/alias/symbol)
(esh-var-test/alias/symbol-pair, esh-var-test/alias/export)
(esh-var-test/alias/local-variables): New tests.

* doc/misc/eshell.texi (Built-ins): Add 'set' and update 'unset'
documentation.
(Variables): Expand documentation of how to get/set variables.
---
 doc/misc/eshell.texi              |  49 ++++++++--
 lisp/eshell/esh-cmd.el            |   4 +-
 lisp/eshell/esh-var.el            | 141 +++++++++++++++++++++--------
 test/lisp/eshell/esh-var-tests.el | 145 ++++++++++++++++++++++++++++++
 4 files changed, 293 insertions(+), 46 deletions(-)

diff --git a/doc/misc/eshell.texi b/doc/misc/eshell.texi
index 8036bbd83a..21c1671a21 100644
--- a/doc/misc/eshell.texi
+++ b/doc/misc/eshell.texi
@@ -694,10 +694,18 @@ Built-ins
 This command can be loaded as part of the eshell-xtra module, which is
 disabled by default.
 
+@item set
+@cmindex set
+Set variable values, using the function @code{set} like a command
+(@pxref{Setting Variables,,, elisp, GNU Emacs Lisp Reference Manual}).
+A variable name can be a symbol, in which case it refers to a Lisp
+variable, or a string, referring to an environment variable
+(@pxref{Arguments}).
+
 @item setq
 @cmindex setq
-Set variable values, using the function @code{setq} like a command.
-@xref{Setting Variables,,, elisp, GNU Emacs Lisp Reference Manual}.
+Set variable values, using the function @code{setq} like a command
+(@pxref{Setting Variables,,, elisp, GNU Emacs Lisp Reference Manual}).
 
 @item source
 @cmindex source
@@ -743,7 +751,9 @@ Built-ins
 
 @item unset
 @cmindex unset
-Unset an environment variable.
+Unset one or more variables.  As with @command{set}, a variable name
+can be a symbol, in which case it refers to a Lisp variable, or a
+string, referring to an environment variable.
 
 @item wait
 @cmindex wait
@@ -881,12 +891,35 @@ Built-ins
 
 @node Variables
 @section Variables
-Since Eshell is just an Emacs @acronym{REPL}@footnote{
+@vindex eshell-prefer-lisp-variables
+Since Eshell is a combination of an Emacs @acronym{REPL}@footnote{
 Short for ``Read-Eval-Print Loop''.
-}
-, it does not have its own scope, and simply stores variables the same
-you would in an Elisp program.  Eshell provides a command version of
-@code{setq} for convenience.
+} and a command shell, it can refer to variables from two different
+sources: ordinary Emacs Lisp variables, as well as environment
+variables.  By default, when using a variable in Eshell, it will first
+look in the list of built-in variables, then in the list of
+environment variables, and finally in the list of Lisp variables.  If
+you would prefer to use Lisp variables over environment variables, you
+can set @code{eshell-prefer-lisp-variables} to @code{t}.
+
+You can set variables in a few different ways.  To set a Lisp
+variable, you can use the command @samp{setq @var{name} @var{value}},
+which works much like its Lisp counterpart (@pxref{Setting Variables,
+, , elisp, The Emacs Lisp Reference Manual}).  To set an environment
+variable, use @samp{export @var{name}=@var{value}}.  You can also use
+@samp{set @var{variable} @var{value}}, which sets a Lisp variable if
+@var{variable} is a symbol, or an environment variable if it's a
+string (@pxref{Arguments}).  Finally, you can temporarily set
+environment variables for a single command with
+@samp{@var{name}=@var{value} @var{command} @dots{}}.  This is
+equivalent to:
+
+@example
+@{
+  export @var{name}=@var{value}
+  @var{command} @dots{}
+@}
+@end example
 
 @subsection Built-in variables
 Eshell knows a few built-in variables:
diff --git a/lisp/eshell/esh-cmd.el b/lisp/eshell/esh-cmd.el
index 3f3a1616ee..c5ceb3ffd1 100644
--- a/lisp/eshell/esh-cmd.el
+++ b/lisp/eshell/esh-cmd.el
@@ -261,9 +261,9 @@ eshell-deferrable-commands
 (defcustom eshell-subcommand-bindings
   '((eshell-in-subcommand-p t)
     (eshell-in-pipeline-p nil)
-    (default-directory default-directory)
-    (process-environment (eshell-copy-environment)))
+    (default-directory default-directory))
   "A list of `let' bindings for subcommand environments."
+  :version "29.1"		       ; removed `process-environment'
   :type 'sexp
   :risky t)
 
diff --git a/lisp/eshell/esh-var.el b/lisp/eshell/esh-var.el
index 3c09fc52fb..caf143e1a1 100644
--- a/lisp/eshell/esh-var.el
+++ b/lisp/eshell/esh-var.el
@@ -113,7 +113,7 @@
 (require 'pcomplete)
 (require 'ring)
 
-(defconst eshell-inside-emacs (format "%s,eshell" emacs-version)
+(defvar-local eshell-inside-emacs (format "%s,eshell" emacs-version)
   "Value for the `INSIDE_EMACS' environment variable.")
 
 (defgroup eshell-var nil
@@ -162,8 +162,8 @@ eshell-variable-aliases-list
 	        (car (last eshell-last-arguments))
 	      (eshell-apply-indices eshell-last-arguments
 				    indices quoted))))
-    ("?" eshell-last-command-status)
-    ("$" eshell-last-command-result)
+    ("?" (eshell-last-command-status . nil))
+    ("$" (eshell-last-command-result . nil))
 
     ;; for em-alias.el and em-script.el
     ("0" eshell-command-name)
@@ -176,7 +176,7 @@ eshell-variable-aliases-list
     ("7" ,(lambda () (nth 6 eshell-command-arguments)) nil t)
     ("8" ,(lambda () (nth 7 eshell-command-arguments)) nil t)
     ("9" ,(lambda () (nth 8 eshell-command-arguments)) nil t)
-    ("*" eshell-command-arguments))
+    ("*" (eshell-command-arguments . nil)))
   "This list provides aliasing for variable references.
 Each member is of the following form:
 
@@ -186,6 +186,11 @@ eshell-variable-aliases-list
 compute the string value that will be returned when the variable is
 accessed via the syntax `$NAME'.
 
+If VALUE is a cons (GET . SET), then variable references to NAME
+will use GET to get the value, and SET to set it.  GET and SET
+can be one of the forms described below.  If SET is nil, the
+variable is read-only.
+
 If VALUE is a function, its behavior depends on the value of
 SIMPLE-FUNCTION.  If SIMPLE-FUNCTION is nil, call VALUE with two
 arguments: the list of the indices that were used in the reference,
@@ -193,23 +198,30 @@ eshell-variable-aliases-list
 quoted with double quotes.  For example, if `NAME' were aliased
 to a function, a reference of `$NAME[10][20]' would result in that
 function being called with the arguments `((\"10\") (\"20\"))' and
-nil.
-If SIMPLE-FUNCTION is non-nil, call the function with no arguments
-and then pass its return value to `eshell-apply-indices'.
+nil.  If SIMPLE-FUNCTION is non-nil, call the function with no
+arguments and then pass its return value to `eshell-apply-indices'.
+
+When VALUE is a function, it's read-only by default.  To make it
+writeable, use the (GET . SET) form described above.  If SET is a
+function, it takes two arguments: a list of indices (currently
+always nil, but reserved for future enhancement), and the new
+value to set.
 
-If VALUE is a string, return the value for the variable with that
-name in the current environment.  If no variable with that name exists
-in the environment, but if a symbol with that same name exists and has
-a value bound to it, return that symbol's value instead.  You can
-prefer symbol values over environment values by setting the value
-of `eshell-prefer-lisp-variables' to t.
+If VALUE is a string, get/set the value for the variable with
+that name in the current environment.  When getting the value, if
+no variable with that name exists in the environment, but if a
+symbol with that same name exists and has a value bound to it,
+return that symbol's value instead.  You can prefer symbol values
+over environment values by setting the value of
+`eshell-prefer-lisp-variables' to t.
 
-If VALUE is a symbol, return the value bound to it.
+If VALUE is a symbol, get/set the value bound to it.
 
 If VALUE has any other type, signal an error.
 
 Additionally, if COPY-TO-ENVIRONMENT is non-nil, the alias should be
 copied (a.k.a. \"exported\") to the environment of created subprocesses."
+  :version "29.1"
   :type '(repeat (list string sexp
 		       (choice (const :tag "Copy to environment" t)
                                (const :tag "Use only in Eshell" nil))
@@ -234,6 +246,11 @@ eshell-var-initialize
   ;; changing a variable will affect all of Emacs.
   (unless eshell-modify-global-environment
     (setq-local process-environment (eshell-copy-environment)))
+  (setq-local eshell-subcommand-bindings
+              (append
+               '((process-environment (eshell-copy-environment))
+                 (eshell-variable-aliases-list eshell-variable-aliases-list))
+               eshell-subcommand-bindings))
 
   (setq-local eshell-special-chars-inside-quoting
        (append eshell-special-chars-inside-quoting '(?$)))
@@ -282,9 +299,9 @@ eshell-handle-local-variables
 	     (while (string-match setvar command)
 	       (nconc
 		l (list
-		   (list 'setenv (match-string 1 command)
-			 (match-string 2 command)
-			 (= (length (match-string 2 command)) 0))))
+                   (list 'eshell-set-variable
+                         (match-string 1 command)
+                         (match-string 2 command))))
 	       (setq command (eshell-stringify (car args))
 		     args (cdr args)))
 	     (cdr l))
@@ -328,12 +345,11 @@ eshell/define
 
 (defun eshell/export (&rest sets)
   "This alias allows the `export' command to act as bash users expect."
-  (while sets
-    (if (and (stringp (car sets))
-	     (string-match "^\\([^=]+\\)=\\(.*\\)" (car sets)))
-	(setenv (match-string 1 (car sets))
-		(match-string 2 (car sets))))
-    (setq sets (cdr sets))))
+  (dolist (set sets)
+    (when (and (stringp set)
+               (string-match "^\\([^=]+\\)=\\(.*\\)" set))
+      (eshell-set-variable (match-string 1 set)
+                           (match-string 2 set)))))
 
 (defun pcomplete/eshell-mode/export ()
   "Completion function for Eshell's `export'."
@@ -343,16 +359,28 @@ pcomplete/eshell-mode/export
 	    (eshell-envvar-names)))))
 
 (defun eshell/unset (&rest args)
-  "Unset an environment variable."
-  (while args
-    (if (stringp (car args))
-	(setenv (car args) nil t))
-    (setq args (cdr args))))
+  "Unset one or more variables.
+This is equivalent to calling `eshell/set' for all of ARGS with
+the values of nil for each."
+  (dolist (arg args)
+    (eshell-set-variable arg nil)))
 
 (defun pcomplete/eshell-mode/unset ()
   "Completion function for Eshell's `unset'."
   (while (pcomplete-here (eshell-envvar-names))))
 
+(defun eshell/set (&rest args)
+  "Allow command-ish use of `set'."
+  (let (last-value)
+    (while args
+      (setq last-value (eshell-set-variable (car args) (cadr args))
+            args (cddr args)))
+    last-value))
+
+(defun pcomplete/eshell-mode/set ()
+  "Completion function for Eshell's `set'."
+  (while (pcomplete-here (eshell-envvar-names))))
+
 (defun eshell/setq (&rest args)
   "Allow command-ish use of `setq'."
   (let (last-value)
@@ -566,18 +594,21 @@ eshell-get-variable
 If QUOTED is non-nil, this was invoked inside double-quotes."
   (if-let ((alias (assoc name eshell-variable-aliases-list)))
       (let ((target (nth 1 alias)))
+        (when (and (not (functionp target))
+                   (consp target))
+          (setq target (car target)))
         (cond
          ((functionp target)
           (if (nth 3 alias)
               (eshell-apply-indices (funcall target) indices quoted)
-            (condition-case nil
-	        (funcall target indices quoted)
-              (wrong-number-of-arguments
-               (display-warning
-                :warning (concat "Function for `eshell-variable-aliases-list' "
-                                 "entry should accept two arguments: INDICES "
-                                 "and QUOTED.'"))
-               (funcall target indices)))))
+            (let ((max-arity (cdr (func-arity target))))
+              (if (or (eq max-arity 'many) (>= max-arity 2))
+                  (funcall target indices quoted)
+                (display-warning
+                 :warning (concat "Function for `eshell-variable-aliases-list' "
+                                  "entry should accept two arguments: INDICES "
+                                  "and QUOTED.'"))
+                (funcall target indices)))))
          ((symbolp target)
           (eshell-apply-indices (symbol-value target) indices quoted))
          (t
@@ -594,6 +625,44 @@ eshell-get-variable
 	 (getenv name)))
      indices quoted)))
 
+(defun eshell-set-variable (name value)
+  "Set the variable named NAME to VALUE.
+NAME can be a string (in which case it refers to an environment
+variable or variable alias) or a symbol (in which case it refers
+to a Lisp variable)."
+  (if-let ((alias (assoc name eshell-variable-aliases-list)))
+      (let ((target (nth 1 alias)))
+        (cond
+         ((functionp target)
+          (setq target nil))
+         ((consp target)
+          (setq target (cdr target))))
+        (cond
+         ((functionp target)
+          (funcall target nil value))
+         ((null target)
+          (unless eshell-in-subcommand-p
+            (error "Variable `%s' is not settable" (eshell-stringify name)))
+          (push `(,name ,(lambda () value) t t)
+                eshell-variable-aliases-list)
+          value)
+         ;; Since getting a variable alias with a string target and
+         ;; `eshell-prefer-lisp-variables' non-nil gets the
+         ;; corresponding Lisp variable, make sure setting does the
+         ;; same.
+         ((and eshell-prefer-lisp-variables
+               (stringp target))
+          (eshell-set-variable (intern target) value))
+         (t
+          (eshell-set-variable target value))))
+    (cond
+     ((stringp name)
+      (setenv name value))
+     ((symbolp name)
+      (set name value))
+     (t
+      (error "Unknown variable `%s'" (eshell-stringify name))))))
+
 (defun eshell-apply-indices (value indices &optional quoted)
   "Apply to VALUE all of the given INDICES, returning the sub-result.
 The format of INDICES is:
diff --git a/test/lisp/eshell/esh-var-tests.el b/test/lisp/eshell/esh-var-tests.el
index ad695e45d7..a7ac52ed24 100644
--- a/test/lisp/eshell/esh-var-tests.el
+++ b/test/lisp/eshell/esh-var-tests.el
@@ -25,6 +25,7 @@
 
 (require 'ert)
 (require 'esh-mode)
+(require 'esh-var)
 (require 'eshell)
 
 (require 'eshell-tests-helpers
@@ -439,6 +440,150 @@ esh-var-test/quoted-interp-convert-cmd-split-indices
   (eshell-command-result-equal "echo \"${echo \\\"000 010 020\\\"}[0]\""
                                "000"))
 
+
+;; Variable-related commands
+
+(ert-deftest esh-var-test/set/env-var ()
+  "Test that `set' with a string variable name sets an environment variable."
+  (with-temp-eshell
+   (eshell-match-command-output "set VAR hello" "hello\n")
+   (should (equal (getenv "VAR") "hello")))
+  (should-not (equal (getenv "VAR") "hello")))
+
+(ert-deftest esh-var-test/set/symbol ()
+  "Test that `set' with a symbol variable name sets a Lisp variable."
+  (let (eshell-test-value)
+    (eshell-command-result-equal "set #'eshell-test-value hello"
+                                 "hello")
+    (should (equal eshell-test-value "hello"))))
+
+(ert-deftest esh-var-test/unset/env-var ()
+  "Test that `unset' with a string variable name unsets an env var."
+  (let ((process-environment (cons "VAR=value" process-environment)))
+    (with-temp-eshell
+     (eshell-match-command-output "unset VAR" "\\`\\'")
+     (should (equal (getenv "VAR") nil)))
+    (should (equal (getenv "VAR") "value"))))
+
+(ert-deftest esh-var-test/unset/symbol ()
+  "Test that `unset' with a symbol variable name unsets a Lisp variable."
+  (let ((eshell-test-value "value"))
+    (eshell-command-result-equal "unset #'eshell-test-value" nil)
+    (should (equal eshell-test-value nil))))
+
+(ert-deftest esh-var-test/setq ()
+  "Test that `setq' sets Lisp variables."
+  (let (eshell-test-value)
+    (eshell-command-result-equal "setq eshell-test-value hello"
+                                 "hello")
+    (should (equal eshell-test-value "hello"))))
+
+(ert-deftest esh-var-test/export ()
+  "Test that `export' sets environment variables."
+  (with-temp-eshell
+   (eshell-match-command-output "export VAR=hello" "\\`\\'")
+   (should (equal (getenv "VAR") "hello"))))
+
+(ert-deftest esh-var-test/local-variables ()
+  "Test that \"VAR=value command\" temporarily sets variables."
+  (with-temp-eshell
+   (push "VAR=value" process-environment)
+   (eshell-match-command-output "VAR=hello env" "VAR=hello\n")
+   (should (equal (getenv "VAR") "value"))))
+
+
+;; Variable aliases
+
+(ert-deftest esh-var-test/alias/function ()
+  "Test using a variable alias defined as a function."
+  (with-temp-eshell
+   (push `("ALIAS" ,(lambda () "value") nil t) eshell-variable-aliases-list)
+   (eshell-match-command-output "echo $ALIAS" "value\n")
+   (eshell-match-command-output "set ALIAS hello"
+                                "Variable `ALIAS' is not settable\n"
+                                nil t)))
+
+(ert-deftest esh-var-test/alias/function-pair ()
+  "Test using a variable alias defined as a pair of getter/setter functions."
+  (with-temp-eshell
+   (let ((eshell-test-value "value"))
+     (push `("ALIAS" (,(lambda () eshell-test-value)
+                      . (lambda (_ value)
+                          (setq eshell-test-value (upcase value))))
+             nil t)
+           eshell-variable-aliases-list)
+     (eshell-match-command-output "echo $ALIAS" "value\n")
+     (eshell-match-command-output "set ALIAS hello" "HELLO\n")
+     (should (equal eshell-test-value "HELLO")))))
+
+(ert-deftest esh-var-test/alias/string ()
+  "Test using a variable alias defined as a string.
+This should get/set the aliased environment variable."
+  (with-temp-eshell
+   (let ((eshell-test-value "lisp-value"))
+     (push "eshell-test-value=env-value" process-environment)
+     (push `("ALIAS" "eshell-test-value") eshell-variable-aliases-list)
+     (eshell-match-command-output "echo $ALIAS" "env-value\n")
+     (eshell-match-command-output "set ALIAS hello" "hello\n")
+     (should (equal (getenv "eshell-test-value") "hello"))
+     (should (equal eshell-test-value "lisp-value")))))
+
+(ert-deftest esh-var-test/alias/string/prefer-lisp ()
+  "Test using a variable alias defined as a string.
+This sets `eshell-prefer-lisp-variables' to t and should get/set
+the aliased Lisp variable."
+  (with-temp-eshell
+   (let ((eshell-test-value "lisp-value")
+         (eshell-prefer-lisp-variables t))
+     (push "eshell-test-value=env-value" process-environment)
+     (push `("ALIAS" "eshell-test-value") eshell-variable-aliases-list)
+     (eshell-match-command-output "echo $ALIAS" "lisp-value\n")
+     (eshell-match-command-output "set ALIAS hello" "hello\n")
+     (should (equal (car process-environment) "eshell-test-value=env-value"))
+     (should (equal eshell-test-value "hello")))))
+
+(ert-deftest esh-var-test/alias/symbol ()
+  "Test using a variable alias defined as a symbol.
+This should get/set the value bound to the symbol."
+  (with-temp-eshell
+   (let ((eshell-test-value "value"))
+     (push '("ALIAS" eshell-test-value) eshell-variable-aliases-list)
+     (eshell-match-command-output "echo $ALIAS" "value\n")
+     (eshell-match-command-output "set ALIAS hello" "hello\n")
+     (should (equal eshell-test-value "hello")))))
+
+(ert-deftest esh-var-test/alias/symbol-pair ()
+  "Test using a variable alias defined as a pair of symbols.
+This should get the value bound to the symbol, but fail to set
+it, since the setter is nil."
+  (with-temp-eshell
+   (let ((eshell-test-value "value"))
+     (push '("ALIAS" (eshell-test-value . nil)) eshell-variable-aliases-list)
+     (eshell-match-command-output "echo $ALIAS" "value\n")
+     (eshell-match-command-output "set ALIAS hello"
+                                "Variable `ALIAS' is not settable\n"
+                                nil t))))
+
+(ert-deftest esh-var-test/alias/export ()
+  "Test that `export' properly sets variable aliases."
+  (with-temp-eshell
+   (let ((eshell-test-value "value"))
+     (push `("ALIAS" (,(lambda () eshell-test-value)
+                      . (lambda (_ value) (setq eshell-test-value value)))
+             nil t)
+           eshell-variable-aliases-list)
+     (eshell-match-command-output "export ALIAS=hello" "\\`\\'")
+     (should (equal eshell-test-value "hello")))))
+
+(ert-deftest esh-var-test/alias/local-variables ()
+  "Test that \"VAR=value cmd\" temporarily sets read-only variable aliases."
+  (with-temp-eshell
+   (let ((eshell-test-value "value"))
+     (push `("ALIAS" ,(lambda () eshell-test-value) t t)
+           eshell-variable-aliases-list)
+     (eshell-match-command-output "ALIAS=hello env" "ALIAS=hello\n")
+     (should (equal eshell-test-value "value")))))
+
 
 ;; Built-in variables
 
-- 
2.25.1

From 5b915a21708332d1b25bd78d3742ae90d93473b2 Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Thu, 15 Sep 2022 12:24:37 -0700
Subject: [PATCH 6/7] Improve handling of $PATH in Eshell for remote
 directories

* lisp/eshell/esh-util.el (eshell-path-env, eshell-parse-colon-path):
Make obsolete.
(eshell-path-env-list): New variable.
(eshell-connection-default-profile): New connection-local profile.
(eshell-get-path): Reimplement using 'eshell-path-env-list'.
(eshell-set-path): New function.

* lisp/eshell/esh-var.el (eshell-variable-aliases-list): Add entry for
$PATH.
(eshell-var-initialize): Add 'eshell-path-env-list' to
'eshell-subcommand-bindings'.

* lisp/eshell/esh-ext.el (eshell-search-path): Use 'file-name-concat'
instead of 'concat'.
(eshell/addpath): Use 'eshell-get-path' and 'eshell-set-path'.

* lisp/net/tramp-integration.el: Only apply Eshell hooks when
'eshell-path-env-list' is unbound.

* test/lisp/eshell/esh-var-tests.el
(esh-var-test/path-var/local-directory)
(esh-var-test/path-var/remote-directory, esh-var-test/path-var/set)
(esh-var-test/path-var/set-locally)
(esh-var-test/path-var-preserve-across-hosts): New tests.

* test/lisp/eshell/esh-ext-tests.el: New file.

* test/lisp/eshell/eshell-tests-helpers.el
(with-temp-eshell): Set 'eshell-last-dir-ring-file-name' to nil.
(eshell-tests-remote-accessible-p, eshell-last-input)
(eshell-last-output): New functions.
(eshell-match-output, eshell-match-output--explainer): Use
'eshell-last-input' and 'eshell-last-output'.

* doc/misc/eshell.texi (Variables): Document $PATH.

* etc/NEWS: Announce this change (bug#57556).
---
 doc/misc/eshell.texi                     | 10 ++++
 etc/NEWS                                 |  5 ++
 lisp/eshell/esh-ext.el                   | 23 ++++---
 lisp/eshell/esh-util.el                  | 53 +++++++++++++++--
 lisp/eshell/esh-var.el                   | 12 +++-
 lisp/net/tramp-integration.el            | 21 +++----
 test/lisp/eshell/esh-ext-tests.el        | 76 ++++++++++++++++++++++++
 test/lisp/eshell/esh-var-tests.el        | 60 +++++++++++++++++++
 test/lisp/eshell/eshell-tests-helpers.el | 32 +++++++---
 9 files changed, 255 insertions(+), 37 deletions(-)
 create mode 100644 test/lisp/eshell/esh-ext-tests.el

diff --git a/doc/misc/eshell.texi b/doc/misc/eshell.texi
index 21c1671a21..d518eafd72 100644
--- a/doc/misc/eshell.texi
+++ b/doc/misc/eshell.texi
@@ -942,6 +942,16 @@ Variables
 directory ring via subscripting, e.g.@: @samp{$-[1]} refers to the
 working directory @emph{before} the previous one.
 
+@vindex $PATH
+@item $PATH
+This specifies the directories to search for executable programs.  Its
+value is a string, separated by @code{":"} for Unix and GNU systems,
+and @code{";"} for MS systems.  This variable is connection-aware, so
+whenever you change the current directory to a different host
+(@pxref{Remote Files, , , emacs, The GNU Emacs Manual}),
+the value will automatically update to reflect the search path on that
+host.
+
 @vindex $_
 @item $_
 This refers to the last argument of the last command.  With a
diff --git a/etc/NEWS b/etc/NEWS
index 72b2331b81..871060148d 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -356,6 +356,11 @@ previous 'C-x ='.
 
 ** Eshell
 
+*** Eshell's PATH is now derived from 'exec-path'.
+For consistency with remote connections, Eshell now uses 'exec-path'
+to determine the execution path on the local system, instead of using
+the PATH environment variable directly.
+
 ---
 *** 'source' and '.' no longer accept the '--help' option.
 This is for compatibility with the shell versions of these commands,
diff --git a/lisp/eshell/esh-ext.el b/lisp/eshell/esh-ext.el
index 98902fc6f2..d513d750d9 100644
--- a/lisp/eshell/esh-ext.el
+++ b/lisp/eshell/esh-ext.el
@@ -77,7 +77,7 @@ eshell-search-path
     (let ((list (eshell-get-path))
 	  suffixes n1 n2 file)
       (while list
-	(setq n1 (concat (car list) name))
+	(setq n1 (file-name-concat (car list) name))
 	(setq suffixes eshell-binary-suffixes)
 	(while suffixes
 	  (setq n2 (concat n1 (car suffixes)))
@@ -239,17 +239,16 @@ eshell/addpath
      (?h "help" nil nil  "display this usage message")
      :usage "[-b] PATH
 Adds the given PATH to $PATH.")
-   (if args
-       (progn
-	 (setq eshell-path-env (getenv "PATH")
-	       args (mapconcat #'identity args path-separator)
-	       eshell-path-env
-	       (if prepend
-		   (concat args path-separator eshell-path-env)
-		 (concat eshell-path-env path-separator args)))
-	 (setenv "PATH" eshell-path-env))
-     (dolist (dir (parse-colon-path (getenv "PATH")))
-       (eshell-printn dir)))))
+   (let ((path (eshell-get-path t)))
+     (if args
+         (progn
+           (setq path (if prepend
+                          (append args path)
+                        (append path args)))
+           (eshell-set-path path)
+           (string-join path (path-separator)))
+       (dolist (dir path)
+         (eshell-printn dir))))))
 
 (put 'eshell/addpath 'eshell-no-numeric-conversions t)
 (put 'eshell/addpath 'eshell-filename-arguments t)
diff --git a/lisp/eshell/esh-util.el b/lisp/eshell/esh-util.el
index 9258ca5e40..55983b1feb 100644
--- a/lisp/eshell/esh-util.el
+++ b/lisp/eshell/esh-util.el
@@ -249,17 +249,58 @@ eshell-path-env
 It might be different from \(getenv \"PATH\"), when
 `default-directory' points to a remote host.")
 
-(defun eshell-get-path ()
+(make-obsolete-variable 'eshell-path-env 'eshell-get-path "29.1")
+
+(defvar-local eshell-path-env-list nil)
+
+(connection-local-set-profile-variables
+ 'eshell-connection-default-profile
+ '((eshell-path-env-list . nil)))
+
+(connection-local-set-profiles
+ '(:application eshell)
+ 'eshell-connection-default-profile)
+
+(defun eshell-get-path (&optional local-part)
   "Return $PATH as a list.
-Add the current directory on MS-Windows."
-  (eshell-parse-colon-path
-   (if (eshell-under-windows-p)
-       (concat "." path-separator eshell-path-env)
-     eshell-path-env)))
+If LOCAL-PART is non-nil, only return the local part of the path.
+Otherwise, return the full, possibly-remote path.
+
+On MS-Windows, add the current directory as the first directory
+in the path."
+  (with-connection-local-application-variables 'eshell
+    (let ((remote (file-remote-p default-directory))
+          (path
+           (or eshell-path-env-list
+               ;; If not already cached, get the path from
+               ;; `exec-path', removing the last element, which is
+               ;; `exec-directory'.
+               (setq-connection-local eshell-path-env-list
+                                      (butlast (exec-path))))))
+      (when (and (eshell-under-windows-p)
+                 (not remote))
+        (push "." path))
+      (if (and remote (not local-part))
+          (mapcar (lambda (x) (file-name-concat remote x)) path)
+        path))))
+
+(defun eshell-set-path (path)
+  "Set the Eshell $PATH to PATH.
+PATH can be either a list of directories or a string of
+directories separated by `path-separator'."
+  (with-connection-local-application-variables 'eshell
+    (setq-connection-local
+     eshell-path-env-list
+     (if (listp path)
+	 path
+       ;; Don't use `parse-colon-path' here, since we don't want
+       ;; the additonal translations it does on each element.
+       (split-string path (path-separator))))))
 
 (defun eshell-parse-colon-path (path-env)
   "Split string with `parse-colon-path'.
 Prepend remote identification of `default-directory', if any."
+  (declare (obsolete nil "29.1"))
   (let ((remote (file-remote-p default-directory)))
     (if remote
 	(mapcar
diff --git a/lisp/eshell/esh-var.el b/lisp/eshell/esh-var.el
index caf143e1a1..57ea42f493 100644
--- a/lisp/eshell/esh-var.el
+++ b/lisp/eshell/esh-var.el
@@ -156,7 +156,14 @@ eshell-variable-aliases-list
     ("LINES" ,(lambda () (window-body-height nil 'remap)) t t)
     ("INSIDE_EMACS" eshell-inside-emacs t)
 
-    ;; for eshell-cmd.el
+    ;; for esh-ext.el
+    ("PATH" (,(lambda () (string-join (eshell-get-path t) (path-separator)))
+             . ,(lambda (_ value)
+                  (eshell-set-path value)
+                  value))
+     t t)
+
+    ;; for esh-cmd.el
     ("_" ,(lambda (indices quoted)
 	    (if (not indices)
 	        (car (last eshell-last-arguments))
@@ -249,7 +256,8 @@ eshell-var-initialize
   (setq-local eshell-subcommand-bindings
               (append
                '((process-environment (eshell-copy-environment))
-                 (eshell-variable-aliases-list eshell-variable-aliases-list))
+                 (eshell-variable-aliases-list eshell-variable-aliases-list)
+                 (eshell-path-env-list eshell-path-env-list))
                eshell-subcommand-bindings))
 
   (setq-local eshell-special-chars-inside-quoting
diff --git a/lisp/net/tramp-integration.el b/lisp/net/tramp-integration.el
index 35c0636b1c..4be019edd9 100644
--- a/lisp/net/tramp-integration.el
+++ b/lisp/net/tramp-integration.el
@@ -136,16 +136,17 @@ tramp-eshell-directory-change
           (getenv "PATH"))))
 
 (with-eval-after-load 'esh-util
-  (add-hook 'eshell-mode-hook
-	    #'tramp-eshell-directory-change)
-  (add-hook 'eshell-directory-change-hook
-	    #'tramp-eshell-directory-change)
-  (add-hook 'tramp-integration-unload-hook
-	    (lambda ()
-	      (remove-hook 'eshell-mode-hook
-			   #'tramp-eshell-directory-change)
-	      (remove-hook 'eshell-directory-change-hook
-			   #'tramp-eshell-directory-change))))
+  (unless (boundp 'eshell-path-env-list)
+    (add-hook 'eshell-mode-hook
+	      #'tramp-eshell-directory-change)
+    (add-hook 'eshell-directory-change-hook
+	      #'tramp-eshell-directory-change)
+    (add-hook 'tramp-integration-unload-hook
+	      (lambda ()
+	        (remove-hook 'eshell-mode-hook
+			     #'tramp-eshell-directory-change)
+	        (remove-hook 'eshell-directory-change-hook
+			     #'tramp-eshell-directory-change)))))
 
 ;;; Integration of recentf.el:
 
diff --git a/test/lisp/eshell/esh-ext-tests.el b/test/lisp/eshell/esh-ext-tests.el
new file mode 100644
index 0000000000..54191e9409
--- /dev/null
+++ b/test/lisp/eshell/esh-ext-tests.el
@@ -0,0 +1,76 @@
+;;; esh-ext-tests.el --- esh-ext test suite  -*- lexical-binding:t -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Tests for Eshell's external command handling.
+
+;;; Code:
+
+(require 'ert)
+(require 'esh-mode)
+(require 'esh-ext)
+(require 'eshell)
+
+(require 'eshell-tests-helpers
+         (expand-file-name "eshell-tests-helpers"
+                           (file-name-directory (or load-file-name
+                                                    default-directory))))
+
+;;; Tests:
+
+(ert-deftest esh-ext-test/addpath/end ()
+  "Test that \"addpath\" adds paths to the end of $PATH."
+  (with-temp-eshell
+   (let ((eshell-path-env-list '("/some/path" "/other/path"))
+         (expected-path (string-join '("/some/path" "/other/path" "/new/path"
+                                       "/new/path2")
+                                     (path-separator))))
+     (eshell-match-command-output "addpath /new/path /new/path2"
+                                  (concat expected-path "\n"))
+     (eshell-match-command-output "echo $PATH"
+                                  (concat expected-path "\n")))))
+
+(ert-deftest esh-ext-test/addpath/begin ()
+  "Test that \"addpath -b\" adds paths to the beginning of $PATH."
+  (with-temp-eshell
+   (let ((eshell-path-env-list '("/some/path" "/other/path"))
+         (expected-path (string-join '("/new/path" "/new/path2" "/some/path"
+                                       "/other/path")
+                                     (path-separator))))
+     (eshell-match-command-output "addpath -b /new/path /new/path2"
+                                  (concat expected-path "\n"))
+     (eshell-match-command-output "echo $PATH"
+                                  (concat expected-path "\n")))))
+
+(ert-deftest esh-ext-test/addpath/set-locally ()
+  "Test adding to the path temporarily in a subcommand."
+  (let* ((eshell-path-env-list '("/some/path" "/other/path"))
+         (original-path (string-join eshell-path-env-list (path-separator)))
+         (local-path (string-join (append eshell-path-env-list '("/new/path"))
+                                  (path-separator))))
+    (with-temp-eshell
+     (eshell-match-command-output
+      "{ addpath /new/path; env }"
+      (format "PATH=%s\n" (regexp-quote local-path)))
+     ;; After the last command, the previous $PATH value should be restored.
+     (eshell-match-command-output "echo $PATH"
+                                  (concat original-path "\n")))))
+
+;; esh-ext-tests.el ends here
diff --git a/test/lisp/eshell/esh-var-tests.el b/test/lisp/eshell/esh-var-tests.el
index a7ac52ed24..31b01c5605 100644
--- a/test/lisp/eshell/esh-var-tests.el
+++ b/test/lisp/eshell/esh-var-tests.el
@@ -23,6 +23,7 @@
 
 ;;; Code:
 
+(require 'tramp)
 (require 'ert)
 (require 'esh-mode)
 (require 'esh-var)
@@ -610,6 +611,65 @@ esh-var-test/inside-emacs-var-split-indices
    (eshell-match-command-output "echo $INSIDE_EMACS[, 1]"
                                 "eshell")))
 
+(ert-deftest esh-var-test/path-var/local-directory ()
+  "Test using $PATH in a local directory."
+  (let ((expected-path (string-join (eshell-get-path t) (path-separator))))
+    (with-temp-eshell
+     (eshell-match-command-output "echo $PATH" (regexp-quote expected-path)))))
+
+(ert-deftest esh-var-test/path-var/remote-directory ()
+  "Test using $PATH in a remote directory."
+  (skip-unless (eshell-tests-remote-accessible-p))
+  (let* ((default-directory ert-remote-temporary-file-directory)
+         (expected-path (string-join (eshell-get-path t) (path-separator))))
+    (with-temp-eshell
+     (eshell-match-command-output "echo $PATH" (regexp-quote expected-path)))))
+
+(ert-deftest esh-var-test/path-var/set ()
+  "Test setting $PATH."
+  (let* ((path-to-set-list '("/some/path" "/other/path"))
+         (path-to-set (string-join path-to-set-list (path-separator))))
+    (with-temp-eshell
+     (eshell-match-command-output (concat "set PATH " path-to-set)
+                                  (concat path-to-set "\n"))
+     (eshell-match-command-output "echo $PATH" (concat path-to-set "\n"))
+     (should (equal (eshell-get-path) path-to-set-list)))))
+
+(ert-deftest esh-var-test/path-var/set-locally ()
+  "Test setting $PATH temporarily for a single command."
+  (let* ((path-to-set-list '("/some/path" "/other/path"))
+         (path-to-set (string-join path-to-set-list (path-separator))))
+    (with-temp-eshell
+     (eshell-match-command-output (concat "set PATH " path-to-set)
+                                  (concat path-to-set "\n"))
+     (eshell-match-command-output "PATH=/local/path env"
+                                  "PATH=/local/path\n")
+     ;; After the last command, the previous $PATH value should be restored.
+     (eshell-match-command-output "echo $PATH" (concat path-to-set "\n"))
+     (should (equal (eshell-get-path) path-to-set-list)))))
+
+(ert-deftest esh-var-test/path-var/preserve-across-hosts ()
+  "Test that $PATH can be set independently on multiple hosts."
+  (let ((local-directory default-directory)
+        local-path remote-path)
+    (with-temp-eshell
+     ;; Set the $PATH on localhost.
+     (eshell-insert-command "set PATH /local/path")
+     (setq local-path (eshell-last-output))
+     ;; `cd' to a remote host and set the $PATH there too.
+     (eshell-insert-command
+      (format "cd %s" ert-remote-temporary-file-directory))
+     (eshell-insert-command "set PATH /remote/path")
+     (setq remote-path (eshell-last-output))
+     ;; Return to localhost and check that $PATH is the value we set
+     ;; originally.
+     (eshell-insert-command (format "cd %s" local-directory))
+     (eshell-match-command-output "echo $PATH" (regexp-quote local-path))
+     ;; ... and do the same for the remote host.
+     (eshell-insert-command
+      (format "cd %s" ert-remote-temporary-file-directory))
+     (eshell-match-command-output "echo $PATH" (regexp-quote remote-path)))))
+
 (ert-deftest esh-var-test/last-status-var-lisp-command ()
   "Test using the \"last exit status\" ($?) variable with a Lisp command"
   (with-temp-eshell
diff --git a/test/lisp/eshell/eshell-tests-helpers.el b/test/lisp/eshell/eshell-tests-helpers.el
index e713e162ad..1d9674070c 100644
--- a/test/lisp/eshell/eshell-tests-helpers.el
+++ b/test/lisp/eshell/eshell-tests-helpers.el
@@ -31,11 +31,22 @@
 (require 'eshell)
 
 (defvar eshell-history-file-name nil)
+(defvar eshell-last-dir-ring-file-name nil)
 
 (defvar eshell-test--max-subprocess-time 5
   "The maximum amount of time to wait for a subprocess to finish, in seconds.
 See `eshell-wait-for-subprocess'.")
 
+(defun eshell-tests-remote-accessible-p ()
+  "Return if a test involving remote files can proceed.
+If using this function, be sure to load `tramp' near the
+beginning of the test file."
+  (ignore-errors
+    (and
+     (file-remote-p ert-remote-temporary-file-directory)
+     (file-directory-p ert-remote-temporary-file-directory)
+     (file-writable-p ert-remote-temporary-file-directory))))
+
 (defmacro with-temp-eshell (&rest body)
   "Evaluate BODY in a temporary Eshell buffer."
   `(save-current-buffer
@@ -44,6 +55,7 @@ with-temp-eshell
               ;; back on $HISTFILE.
               (process-environment (cons "HISTFILE" process-environment))
               (eshell-history-file-name nil)
+              (eshell-last-dir-ring-file-name nil)
               (eshell-buffer (eshell t)))
          (unwind-protect
              (with-current-buffer eshell-buffer
@@ -83,19 +95,25 @@ eshell-insert-command
   (insert-and-inherit command)
   (funcall (or func 'eshell-send-input)))
 
+(defun eshell-last-input ()
+  "Return the input of the last Eshell command."
+  (buffer-substring-no-properties
+   eshell-last-input-start eshell-last-input-end))
+
+(defun eshell-last-output ()
+  "Return the output of the last Eshell command."
+  (buffer-substring-no-properties
+   (eshell-beginning-of-output) (eshell-end-of-output)))
+
 (defun eshell-match-output (regexp)
   "Test whether the output of the last command matches REGEXP."
-  (string-match-p
-    regexp (buffer-substring-no-properties
-            (eshell-beginning-of-output) (eshell-end-of-output))))
+  (string-match-p regexp (eshell-last-output)))
 
 (defun eshell-match-output--explainer (regexp)
   "Explain the result of `eshell-match-output'."
   `(mismatched-output
-    (command ,(buffer-substring-no-properties
-               eshell-last-input-start eshell-last-input-end))
-    (output ,(buffer-substring-no-properties
-              (eshell-beginning-of-output) (eshell-end-of-output)))
+    (command ,(eshell-last-input))
+    (output ,(eshell-last-output))
     (regexp ,regexp)))
 
 (put 'eshell-match-output 'ert-explainer #'eshell-match-output--explainer)
-- 
2.25.1

From 95f021dede1be4b53cd789704543bbfa945442ee Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Thu, 15 Sep 2022 12:32:02 -0700
Subject: [PATCH 7/7] Print the correct $PATH when Eshell's 'which' fails to
 find a command

* lisp/eshell/esh-cmd.el (eshell/which): Use 'eshell-get-path'
(bug#20008).
---
 lisp/eshell/esh-cmd.el | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lisp/eshell/esh-cmd.el b/lisp/eshell/esh-cmd.el
index c5ceb3ffd1..4a41bbe8fa 100644
--- a/lisp/eshell/esh-cmd.el
+++ b/lisp/eshell/esh-cmd.el
@@ -1274,8 +1274,9 @@ eshell/which
                         name)
                   (eshell-search-path name)))))
       (if (not program)
-	  (eshell-error (format "which: no %s in (%s)\n"
-				name (getenv "PATH")))
+          (eshell-error (format "which: no %s in (%s)\n"
+                                name (string-join (eshell-get-path t)
+                                                  (path-separator))))
 	(eshell-printn program)))))
 
 (put 'eshell/which 'eshell-no-numeric-conversions t)
-- 
2.25.1