bug#33016: 26.1; (make-process ...) doesn't signal an error, when executable given as absolute Windows path does not exist

[Eli Zaretskii <eliz@gnu.org>]

> From: Klaus-Dieter Bauer <bauer.klaus.dieter@gmail.com>
> Date: Thu, 11 Oct 2018 14:55:27 +0200
> 
> Entering
> 
>     M-x eval-expression RET
>       (make-process :name "test" :command '("No Such Command"))
> 
> will bring up the debugger with 
> 
>     (file-missing "Searching for program" "No such file or directory" "nosuchcommand")
> 
> However, entering
> 
>     M-x eval-expression RET 
>       (make-process :name "test" :command '("c:/No Such Command"))
> 
> will merely display in the echo-area message:
> 
>     eval: Spawning child process: Invalid argument
> 
> I stumbled upon this when debugging a quick-and-dirty
> script, that called a program by absolute path. When a new
> version of the program changed the name of the executable
> (tex2lyx2.3 -> tex2lyx), this issue occurred, and hindered
> debugging the problem.
> 
> The wording of the message might indicate a 
> Windows-specific issue.

The error in the second case is Windows specific, but the
inconsistency isn't: on Unix the second case "succeeds", in that it
returns a process object without any error messages.

The error message you see in the first case is because Emacs searches
for the program along exec-path (because it is not an absolute file
name).  In the second case this search is not done, because the file
name is already absolute.

So I don't think this is a bug.