bug#61014: 29.0.60; flymake-mode stderr warning is confusing when edit the init.el or eary-init.el

[Eli Zaretskii <eliz@gnu.org>]

> From: João Távora <joaotavora@gmail.com>
> Cc: Eason Huang <aqua0210@foxmail.com>,  61014@debbugs.gnu.org
> Date: Thu, 26 Jan 2023 11:16:39 +0000
> 
> First of all, let's make it clear that this warning happens in a hidden
> Flymake buffer, an implementation detail which stores the stderr output
> of the subprocess(es) invoked.  It does not appear in the interactive
> seeion's *Warnings* buffer.  Unless I've missed something, the user is
> never confronted with it or hindered by it in any way.  It seems to be
> largely benign.
> 
> The warning only become visible when switching to a specific hidden
> buffer, like Eason did, and that operation is more accurately described
> as an introspection feature intended for developers, not for users.
> 
> So, to summarize, the warning is coming from the subprocess
> non-interactive Emacs spawned by the interactive Emacs where
> flymake-mode is turned on.  In the interactive Emacs session, nothing
> special is going on.
> 
> The reason elisp-flymake-byte-compile-load-path has a default value of
> "./" is to help with the primary use case for the
> elisp-flymake-byte-compile Flymake backend: developing libraries that
> `require` other .el libraries.  Such .el files often live in the same
> directory of the file/buffer you are editing with flymake-mode turned
> on.  So when you're editing x/y/z/foo.el and you type
> 
>   (require 'foo-utils)
> 
> elisp-flymake-byte-compile will understand that to syntax-check foo.el
> with the byte-compiler it needs to load "x/u/z/foo-utils.el".
> 
> In Eason's case, the user happens to be editing a .el file in a special
> Emacs directory where such a use case is unlikely (though not
> impossible).  So every few changes the user does to the buffer,
> flymake-mdoe will invoke a Emacs subprocess and give it this particular
> load-path initialization, that, in the specific acse of ~/.emacs.d, is
> slightly non-orthodox.  And thus the subprocess emacs complains with
> this warning which is recorded in the special hidden buffer.
> 
> If we're really worries about this, we could special-case this directory
> elisp-mode.el.  But I also don't see what the harm could be.  So my
> advice is to only do this when someone describes real harm.

How about disabling this warning in non-interactive sessions?  That
should be easy, and I don't see why we would want to emit such a
warning in non-interactive sessions anyway.

Stefan, am I missing something?