From 88accc0c92639355ce8a1c62cfaac0e07bc09de9 Mon Sep 17 00:00:00 2001
From: Lin Jian <me@linj.tech>
Date: Sun, 27 Sep 2026 18:55:45 +0800
Subject: [PATCH] emacs: use PATH instead of exec-path to expose wrapped
 binaries
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(info "(elisp) Subprocess Creation") says:

> Generally, you should not modify ‘exec-path’ directly.  Instead,
> ensure that your ‘PATH’ environment variable is set appropriately
> before starting Emacs.  Trying to modify ‘exec-path’ independently
> of ‘PATH’ can lead to confusing results.

One example of "confusing results" can be found in envrc[1].

This patch follows that recommendation of Emacs lisp manual.

In addition, we added tests for PATH and exec-path.

[1]: https://github.com/purcell/envrc/issues/9
---
 .../wrapper-test/with-packages.el             | 27 +++++++++++++++++--
 .../editors/emacs/build-support/wrapper.nix   |  5 ++--
 .../editors/emacs/build-support/wrapper.sh    |  5 ++++
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/pkgs/applications/editors/emacs/build-support/wrapper-test/with-packages.el b/pkgs/applications/editors/emacs/build-support/wrapper-test/with-packages.el
index 9f0ed7920c2a..30735966656d 100644
--- a/pkgs/applications/editors/emacs/build-support/wrapper-test/with-packages.el
+++ b/pkgs/applications/editors/emacs/build-support/wrapper-test/with-packages.el
@@ -41,6 +41,13 @@ which is generated by nix when building this elisp package."
 (defun with-packages-unwrapped-site-start-is-loaded ()
   (fboundp 'nix--profile-paths))
 
+(defun with-packages-eval-in-sub-emacs (form)
+  "Evaluate FORM in a subprocess Emacs and return its result."
+  (pcase-exhaustive
+      (process-lines "emacs" "--batch"
+                     "--eval" (format "(prin1 %S)" form))
+    (`(,result) (read result))))
+
 ;;;; Tests that can be run in a batch Emacs
 
 (ert-deftest with-packages-requested-packages-are-available ()
@@ -71,8 +78,24 @@ which is generated by nix when building this elisp package."
 (ert-deftest with-packages-unwrapped-site-start-is-loaded ()
   (should (with-packages-unwrapped-site-start-is-loaded)))
 
-(ert-deftest with-packages-bin-dirs-of-requested-packages-are-added-to-exec-path ()
-  (should (executable-find "cowsay")))
+(ert-deftest with-packages-binaries-of-requested-packages-are-available ()
+  (ert-info ("find binary via PATH")
+    (should (equal (call-process-shell-command "cowsay") 0)))
+  (ert-info ("find binary via exec-path")
+    (should (executable-find "cowsay")))
+  (ert-info ("each item is unique")
+    (cl-flet ((item-should-be-unique (items)
+                (should (equal items
+                               (cl-remove-duplicates items :test #'string=)))))
+      (ert-info ("PATH of this Emacs")
+        (item-should-be-unique (parse-colon-path (getenv "PATH"))))
+      (ert-info ("PATH of sub-Emacs")
+        (item-should-be-unique
+         (parse-colon-path (with-packages-eval-in-sub-emacs '(getenv "PATH")))))
+      (ert-info ("exec-path of this Emacs")
+        (item-should-be-unique exec-path))
+      (ert-info ("exec-path of sub-Emacs")
+        (item-should-be-unique (with-packages-eval-in-sub-emacs 'exec-path))))))
 
 (ert-deftest with-packages-tree-sitter-dir-is-added-to-treesit-extra-load-path ()
   (skip-unless (treesit-available-p))
diff --git a/pkgs/applications/editors/emacs/build-support/wrapper.nix b/pkgs/applications/editors/emacs/build-support/wrapper.nix
index 782fa7681974..1f9fbb240c5a 100644
--- a/pkgs/applications/editors/emacs/build-support/wrapper.nix
+++ b/pkgs/applications/editors/emacs/build-support/wrapper.nix
@@ -171,9 +171,6 @@ runCommand (lib.appendToName "with-packages" emacs).name
           cat >"$siteStart" <<EOF
           ;;; -*- lexical-binding: t -*-
           (load "$emacs/share/emacs/site-lisp/site-start" nil t)
-          ;; "$out/share/emacs/site-lisp" is added to load-path in wrapper.sh
-          ;; "$out/share/emacs/native-lisp" is added to native-comp-eln-load-path in wrapper.sh
-          (add-to-list 'exec-path "$out/bin")
           ${lib.optionalString withTreeSitter ''
             (add-to-list 'treesit-extra-load-path "$out/lib/")
           ''}
@@ -213,6 +210,7 @@ runCommand (lib.appendToName "with-packages" emacs).name
         --subst-var-by bash ${emacs.stdenv.shell} \
         --subst-var-by wrapperSiteLisp "$deps/share/emacs/site-lisp" \
         --subst-var-by wrapperSiteLispNative "$deps/share/emacs/native-lisp" \
+        --subst-var-by wrapperBinDir "$deps/bin" \
         --subst-var-by wrapperInvocationDirectory "$out/bin/" \
         --subst-var-by wrapperInvocationName "$progname" \
         --subst-var prog
@@ -239,6 +237,7 @@ runCommand (lib.appendToName "with-packages" emacs).name
         --subst-var-by bash ${emacs.stdenv.shell} \
         --subst-var-by wrapperSiteLisp "$deps/share/emacs/site-lisp" \
         --subst-var-by wrapperSiteLispNative "$deps/share/emacs/native-lisp" \
+        --subst-var-by wrapperBinDir "$deps/bin" \
         --subst-var-by wrapperInvocationDirectory "$out/Applications/Emacs.app/Contents/MacOS/" \
         --subst-var-by wrapperInvocationName "Emacs" \
         --subst-var-by prog "$emacs/Applications/Emacs.app/Contents/MacOS/Emacs"
diff --git a/pkgs/applications/editors/emacs/build-support/wrapper.sh b/pkgs/applications/editors/emacs/build-support/wrapper.sh
index e83308bf5b32..fb334eaf32e4 100755
--- a/pkgs/applications/editors/emacs/build-support/wrapper.sh
+++ b/pkgs/applications/editors/emacs/build-support/wrapper.sh
@@ -53,4 +53,9 @@ export emacsWithPackages_siteLispNative=@wrapperSiteLispNative@
 export emacsWithPackages_invocationDirectory=@wrapperInvocationDirectory@
 export emacsWithPackages_invocationName=@wrapperInvocationName@
 
+if [[ ${PATH-} != *"@wrapperBinDir@":* ]]
+then
+    export PATH="@wrapperBinDir@${PATH:+:$PATH}"
+fi
+
 exec @prog@ "$@"