bug#64198: Feature request: compile.el's "Find this in" prompt should be hookable.

[Eli Zaretskii]

> From: Dave Abrahams <dave@boostpro.com>
> Date: Thu, 22 Jun 2023 10:11:29 -0700
> Cc: 64198@debbugs.gnu.org
> 
> > On Jun 22, 2023, at 10:02 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> From: Dave Abrahams <dave@boostpro.com>
> >> Date: Wed, 21 Jun 2023 09:09:08 -0700
> >> Cc: 64198@debbugs.gnu.org
> >> 
> >> Before discussing patches, could you please describe your situation?
> >> Specifically, how does it happen that neither the compilation
> >> directory plus the file name shown by the diagnostics nor the search
> >> of compilation-search-path succeed to locate the file?  And what would
> >> the hook function you suggest adding do to resolve this, i.e. how
> >> would it know where to look for the file?
> >> 
> >> When Swift asserts, it doesn't write the path to the file into the output, 
> >> because… reasons I grudgingly
> >> accept.  So one needs to guess at the file.  
> >> https://github.com/apple/swift/issues/66777 contains all the
> >> details, but if you want additional info, please ask.
> > 
> > I don't know what Swift is, and that issue talks about something
> > called #fileID, which I again have no idea about.  So yes, please do
> > elaborate, and TIA.
> 
> Swift is a programming language.  When its assertions (like C's assert() 
> macro) fail, a diagnostic is output with a file ID and line. The file ID 
> looks like a path, but it's really not. If it's a path in the filesystem, 
> that's coincidental but it's likely to point to the right file.  I don't want 
> to manually hunt down the file every time an assertion fails; I'd rather 
> emacs made an educated guess based on the current project.  It's obviously 
> not the right answer for everyone, but I'd like to have the hooks needed to 
> implement that without too much hackery.

I'm okay with adding a hook function which will be called from
compilation-find-file if compilation-find-file-1 fails to find the
file.  But I must say that you are trying to use compilation-mode in a
situation for which it was never been designed to be used.