GNU bug report logs - #49918
28.0.50; cd function expands CDPATH incorrectly

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Phil Hagelberg <phil <at> hagelb.org>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.0.50; cd function expands CDPATH incorrectly
Date: Fri, 06 Aug 2021 18:18:10 -0700

When using the function `cd' with a relative path and the $CDPATH
environment variable set, it will expand the value of $CDPATH once and
save off that expansion for future use. This causes all calls with
relative paths to fail when run from a different directory.

This reproduces the problem using eshell, but the bug affects any caller
of the `cd' function, not just eshell. However, it does not affect M-x
cd, which will always use absolute paths.

    CDPATH=.:$HOME/src emacs -Q
    M-x eshell
    cd /
    cd tmp
    No such directory found via CDPATH environment variable: tmp

This happens because of this snippet inside the `cd' function:

    (unless cd-path
      (setq cd-path (or (parse-colon-path (getenv "CDPATH"))
                        (list "./"))))

The behavior of the `parse-colon-path' function changed in 2020 in
commit 76098d39c992aa51f5bdb04fb39e40fc5eb409d5:

-    (mapcar (lambda (f)
-	      (if (equal "" f) nil
-		(substitute-in-file-name (file-name-as-directory f))))
-	    (split-string search-path path-separator))))
+    (let ((spath (substitute-env-vars search-path)))
+      (mapcar (lambda (f)
+                (if (equal "" f) nil
+                  (let ((dir (expand-file-name (file-name-as-directory f))))
+                    ;; Previous implementation used `substitute-in-file-name'
+                    ;; which collapse multiple "/" in front.  Do the same for
+                    ;; backward compatibility.
+                    (if (string-match "\\`/+" dir)
+                        (substring dir (1- (match-end 0))) dir))))
+              (split-string spath path-separator)))))

Previous behavior did not expand relative paths like "." but the new
behavior does. That means that the above call which sets cd-path cannot
use this function as is. Either the old behavior of parse-colon-path
will need to be brought back, or `cd' needs to no longer call that function.

Witness on the current master branch: ($PWD here is ~/src/emacs)

    (parse-colon-path ".:/hey") : -> ("/home/phil/src/emacs/" "/hey/")

Whereas on 27, you get this:

    (parse-colon-path ".:/hey") : -> ("./" "/hey/")

The old behavior is safe to set for the value of `cd-path' but the new
behavior is not.


In GNU Emacs 28.0.50 (build 1, aarch64-unknown-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)
 of 2021-08-06 built on reform
Repository revision: 0b049fe71d73f6885a3c81ea31829e3befc18933
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12099001
System Description: Debian GNU/Linux 11 (bullseye)

Configured using:
 'configure --with-cairo --with-modules --without-compress-install
 --with-gnutls --without-gconf --without-xaw3d --without-gsettings
 --with-mailutils --with-native-compilation --with-json --with-harfbuzz
 --without-imagemagick --with-jpeg --with-png --with-rsvg --with-tiff
 --with-wide-int --with-xft --with-xml2 --with-xpm 'CFLAGS=-O3
 -mtune=native -march=native -fomit-frame-pointer' prefix=/usr/local'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM HARFBUZZ JPEG JSON LCMS2
LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NATIVE_COMP NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
X11 XDBE XIM XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Diff

Minor modes in effect:
  recentf-mode: t
  whitespace-mode: t
  global-company-mode: t
  company-mode: t
  shell-dirtrack-mode: t
  winner-mode: t
  show-paren-mode: t
  save-place-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
~/.emacs.d//phil/../custom hides /home/phil/src/emacs/lisp/custom

Features:
(shadow sort mail-extr emacsbug message rmc dired dired-loaddefs rfc822
mml mml-sec epa derived epg epg-config mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail hippie-exp
sh-script executable smerge-mode diff flyspell ispell mhtml-mode
css-mode smie eww xdg url-queue shr kinsoku svg xml browse-url puny
mm-url gnus nnheader gnus-util rmail rmail-loaddefs rfc2047 rfc2045
ietf-drums mail-utils mm-util mail-prsvr js cc-mode cc-fonts cc-guess
cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs sgml-mode
facemenu dom scpaste htmlize url url-proxy url-privacy url-expand
url-methods url-history url-cookie url-domsuf url-util url-parse
auth-source password-cache json map url-vars mailcap cl-print pulse
color xref project eieio eieio-core eieio-loaddefs ielm pp tabify
vc-annotate imenu hi-lock misearch multi-isearch add-log log-view
pcvs-util vc vc-git diff-mode easy-mmode vc-dispatcher bug-reference
find-func shortdoc text-property-search em-tramp em-xtra help-fns
radix-tree recentf tree-widget wid-edit pcmpl-unix time-date paredit
whitespace idle-highlight-mode thingatpt hl-line company-dabbrev-code
company-dabbrev company-files company-capf company pcase em-unix em-term
term disp-table shell ehelp em-script em-prompt em-ls em-hist em-pred
em-glob em-dirs esh-var em-cmpl pcomplete comint ansi-color em-basic
em-banner em-alias esh-mode eshell esh-cmd esh-ext esh-opt esh-proc
esh-io esh-arg esh-module esh-groups esh-util winner ring smex comp
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my-autoload paren edmacro kmacro cl-loaddefs cl-lib saveplace ido seq
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electric uniquify ediff-hook vc-hooks lisp-float-type mwheel term/x-win
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cp51932 hebrew greek romanian slovak czech european ethiopic indian
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hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting font-render-setting cairo move-toolbar gtk x-toolkit x
multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 348427 19451)
 (symbols 48 19549 1)
 (strings 32 73704 4571)
 (string-bytes 1 2519167)
 (vectors 16 37842)
 (vector-slots 8 705331 23605)
 (floats 8 380 691)
 (intervals 56 21516 4320)
 (buffers 992 29))

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