Subject: Re: bug#8340: 23.2; recompile does not retain compilation-environment needed by vc-git-grep

From: Stefan Monnier <[email-masked]>
Date: Tue, 06 Sep 2011 14:39:58 -0400

> -(defvar compilation-environment nil
> -  "*List of environment variables for compilation to inherit.
> +(defcustom compilation-environment nil
> +  "List of environment variables for compilation to inherit.
>  Each element should be a string of the form ENVVARNAME=VALUE.
>  This list is temporarily prepended to `process-environment' prior to
> -starting the compilation process.")
> +starting the compilation process."
> +  :type '(repeat (string :tag "ENVVARNAME=VALUE"))
> +  :options '(("LANG=C"))
> +  :group 'compilation
> +  :version "24.1")

What is this supposed to fix?

>  ;; History of compile commands.
>  (defvar compile-history nil)
> @@ -1482,6 +1491,7 @@ (defun compilation-start (command &optio
>  	      "compilation"
>  	    (replace-regexp-in-string "-mode\\'" "" (symbol-name mode))))
>  	 (thisdir default-directory)
> +	 (thisenv compilation-environment)
>  	 outwin outbuf)
>      (with-current-buffer
>  	(setq outbuf
> @@ -1530,6 +1541,7 @@ (defun compilation-start (command &optio
>          ;; affected by the special handling of "cd ...;".
>          ;; NB: must be fone after (funcall mode) as that resets local variables
>          (set (make-local-variable 'compilation-directory) thisdir)
> +	(set (make-local-variable 'compilation-environment) thisenv)
>  	(if highlight-regexp
>  	    (set (make-local-variable 'compilation-highlight-regexp)
>  		 highlight-regexp))

> === modified file 'lisp/vc/vc-git.el'
> --- lisp/vc/vc-git.el	2011-09-01 07:29:56 +0000
> +++ lisp/vc/vc-git.el	2011-09-06 09:19:48 +0000
> @@ -998,7 +998,7 @@ (defun vc-git-grep (regexp &optional fil
>  	    (add-to-history 'grep-history command))))
>        (when command
>  	(let ((default-directory dir)
> -	      (compilation-environment '("PAGER=")))
> +	      (compilation-environment (cons "PAGER=" compilation-environment)))
>  	  ;; Setting process-setup-function makes exit-message-function work
>  	  ;; even when async processes aren't supported.
>  	  (compilation-start command 'grep-mode))

Mixing defcustom+bufferlocal+letbinding is really asking for trouble,
although I think in this case it might just fall within the limits of
what does work.
The vc-git.el patch looks perfectly good and so does the (set...thisenv).
But I'd prefer to refrain from making compilation-environment a defcustom
for now, until we find a really good use for it.

        Stefan