From b9455643a4636fc00548917176d059130d91460d Mon Sep 17 00:00:00 2001
From: ncaq <ncaq@ncaq.net>
Date: Tue, 29 Apr 2025 16:23:34 +0900
Subject: [PATCH] fix: run shell with clean environment

The problem was that Nix's initialization script checks for an environment variable
(`__ETC_PROFILE_NIX_SOURCED`) to prevent duplicate execution.
When Emacs calls a shell process,
this variable is inherited,
causing the Nix `PATH` setup to be skipped.
This commit adds a function to run call-process with empty process-environment,
ensuring shell initialization scripts run completely fresh,
properly including Nix paths in the returned environment variables.
---
 exec-path-from-shell.el | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/exec-path-from-shell.el b/exec-path-from-shell.el
index a6e9abb..a0dd24c 100644
--- a/exec-path-from-shell.el
+++ b/exec-path-from-shell.el
@@ -157,6 +157,26 @@ The limit is given by `exec-path-from-shell-warn-duration-millis'."
                (message "Warning: exec-path-from-shell execution took %dms. See the README for tips on reducing this." ,duration-millis)
              (exec-path-from-shell--debug "Shell execution took %dms" ,duration-millis)))))))
 
+(defun exec-path-from-shell--call-process-with-clean-env (program &optional infile destination display &rest args)
+  "Call PROGRAM with a completely clean environment.
+
+This function is a thin wrapper around `call-process'.
+It binds `process-environment' to an empty list so that no inherited
+environment variables from Emacs (e.g. PATH, LANG)
+ are passed to the subprocess.
+
+Arguments are the same as for `call-process':
+
+  PROGRAM     — the executable to run (string)
+  INFILE      — nil, t, or a file name for standard input
+  DESTINATION — nil, t, or a buffer/file for standard output
+  DISPLAY     — if non-nil, redisplay buffer as output is inserted
+  ARGS        — additional arguments passed to PROGRAM
+
+Returns the exit code of the called process."
+  (let ((process-environment nil))
+    (apply #'call-process program infile destination display args)))
+
 (defun exec-path-from-shell-printf (str &optional args)
   "Return the result of printing STR in the user's shell.
 
@@ -183,7 +203,7 @@ shell-escaped, so they may contain $ etc."
     (with-temp-buffer
       (exec-path-from-shell--debug "Invoking shell %s with args %S" shell shell-args)
       (let ((exit-code (exec-path-from-shell--warn-duration
-                        (apply #'call-process shell nil t nil shell-args))))
+                        (apply #'exec-path-from-shell--call-process-with-clean-env shell nil t nil shell-args))))
         (exec-path-from-shell--debug "Shell printed: %S" (buffer-string))
         (unless (zerop exit-code)
           (error "Non-zero exit code from shell %s invoked with args %S.  Output was:\n%S"
@@ -209,7 +229,7 @@ The result is a list of (NAME . VALUE) pairs."
     (with-temp-buffer
       (exec-path-from-shell--debug "Invoking shell %s with args %S" shell shell-args)
       (let ((exit-code (exec-path-from-shell--warn-duration
-                        (apply #'call-process shell nil t nil shell-args))))
+                        (apply #'exec-path-from-shell--call-process-with-clean-env shell nil t nil shell-args))))
         (exec-path-from-shell--debug "Shell printed: %S" (buffer-string))
         (unless (zerop exit-code)
           (error "Non-zero exit code from shell %s invoked with args %S.  Output was:\n%S"