GNU bug report logs - #8531
eshell backslash handling

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Message #60 received at 8531 <at> debbugs.gnu.org (full text, mbox):

From: samer <samer <at> samertm.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#8531: 24.0.50;
Date: Mon, 08 Dec 2014 16:15:17 -0800

Forgot to CC debbugs in my previous email:

This is the full patch, generated with magit because I couldn't commit 
this to a private branch (I get "Empty change log entry" even though 
I've changed both ChangeLog files. I don't know awk, do you have any 
idea why I would get that error?)

Best,
Samer

Changes from master to working tree
4 files changed, 26 insertions(+), 22 deletions(-)
 etc/ChangeLog          |  4 ++++
 etc/NEWS               |  6 ++++++
 lisp/ChangeLog         |  7 +++++++
 lisp/eshell/esh-arg.el | 31 +++++++++----------------------

	Modified   etc/ChangeLog
diff --git a/etc/ChangeLog b/etc/ChangeLog
index 309c01f..3e76256 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,7 @@
+2014-12-08  Samer Masterson  <samer <at> dark-horse>
+
+	* NEWS: Mention change in backslash expand behavior for eshell.
+
 2014-12-08  Lars Magne Ingebrigtsen  <larsi <at> gnus.org>

 	* NEWS: Mention the new eww `S' command.
	Modified   etc/NEWS
diff --git a/etc/NEWS b/etc/NEWS
index 56036f8..e6d9aab 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -192,6 +192,12 @@ result of the calculation into the current buffer.
 *** New minor mode global-eldoc-mode
 *** eldoc-documentation-function now defaults to nil

+** eshell
+
+*** Backslash (\) expands to the character literal after it if that
+character is non-special (e.g. 'b\in' expands to 'bin', because 'i' is
+not a special character). This behavior conforms with bash.
+
 ** eww

 +++
	Modified   lisp/ChangeLog
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 2669e07..0ec9b35 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2014-12-08  Samer Masterson  <samer <at> samertm.com>
+
+	* eshell/esh-arg.el (eshell-parse-backslash): Return the literal
+	character after the backslash if the character is non-special
+	(bug#8531).
+	(eshell-looking-at-backslash-return): Unused, remove.
+
 2014-12-08  Lars Magne Ingebrigtsen  <larsi <at> gnus.org>

 	* net/nsm.el (nsm-check-protocol): Test for RC4 on `high'.
	Modified   lisp/eshell/esh-arg.el
diff --git a/lisp/eshell/esh-arg.el b/lisp/eshell/esh-arg.el
index 704de57..33ff384 100644
--- a/lisp/eshell/esh-arg.el
+++ b/lisp/eshell/esh-arg.el
@@ -89,7 +89,8 @@ yield the values intended."
 	  (goto-char (match-end 0))
 	  (eshell-finish-arg)))))

-   ;; backslash before a special character means escape it
+   ;; backslash before a character escapes it if the character is
+   ;; special, and returns the character literal if it is non-special
    'eshell-parse-backslash

    ;; text beginning with ' is a literally quoted
@@ -282,13 +283,6 @@ Point is left at the end of the arguments."
   "A stub function that generates an error if a floating operator is 
found."
   (error "Unhandled operator in input text"))

-(defsubst eshell-looking-at-backslash-return (pos)
-  "Test whether a backslash-return sequence occurs at POS."
-  (and (eq (char-after pos) ?\\)
-       (or (= (1+ pos) (point-max))
-	   (and (eq (char-after (1+ pos)) ?\n)
-		(= (+ pos 2) (point-max))))))
-
 (defun eshell-quote-backslash (string &optional index)
   "Intelligently backslash the character occurring in STRING at INDEX.
 If the character is itself a backslash, it needs no escaping."
@@ -305,9 +299,11 @@ If the character is itself a backslash, it needs no 
escaping."
 	  (string ?\\ char)))))

 (defun eshell-parse-backslash ()
-  "Parse a single backslash (\) character, which might mean escape.
-It only means escape if the character immediately following is a
-special character that is not itself a backslash."
+  "Parse a single backslash (\) character to escape the character 
after.
+If the character immediately following the backslash is a special
+character, it returns the escaped version of that character.
+Else, the character has no meaning and is returned as the literal
+character. This conforms with the behavior of bash."
   (when (eq (char-after) ?\\)
     (if (eshell-looking-at-backslash-return (point))
 	(throw 'eshell-incomplete ?\\)
@@ -321,18 +317,9 @@ special character that is not itself a backslash."
 	    (forward-char 2)
 	    (list 'eshell-escape-arg
 		  (char-to-string (char-before))))
-	;; allow \\<RET> to mean a literal "\" character followed by a
-	;; normal return, rather than a backslash followed by a line
-	;; continuation (i.e., "\\ + \n" rather than "\ + \\n").  This
-	;; is necessary because backslashes in Eshell are not special
-	;; unless they either precede something special, or precede a
-	;; backslash that precedes something special.  (Mainly this is
-	;; done to make using backslash on Windows systems more
-	;; natural-feeling).
-	(if (eshell-looking-at-backslash-return (1+ (point)))
-	    (forward-char))
 	(forward-char)
-	"\\"))))
+	(forward-char)
+	(char-before)))))

 (defun eshell-parse-literal-quote ()
   "Parse a literally quoted string.  Nothing has special meaning!"

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