bug#3418: Issue with compile.el and compilation-parse-errors-filename-function

[Gary Oberbrunner <garyo@genarts.com>]

Hi emacs folks.  I submitted a patch to compilation-get-file-structure 
in compile.el in 2001, introducing this stanza:

	;; If compilation-parse-errors-filename-function is
	;; defined, use it to process the filename.
	(when compilation-parse-errors-filename-function
	  (setq filename
		(funcall
			 filename)))

At some point since then, the filename was changed to not always be 
absolute; there's now a variable spec-directory in that function.  This 
means that implementations of compilation-parse-errors-filename-function 
can't always work correctly since it doesn't know the full path of the file.

I'm happy to work on a fix, but I see a few issues.

Solution 1: add 2nd arg SPEC-DIRECTORY to 
compilation-parse-errors-filename-function.
Problem: existing implementations will get an incorrect number of args 
error and will have to change.

Solution 2: make filename absolute before passing to 
compilation-parse-errors-filename-function.
Problem: the rest of the code is pretty careful not to absolutize the 
filename; this would change the behavior in ways I don't completely 
understand.

Of course I am personally happy with solution 1, but since it affects 
compatibility I thought I should bring it up on this list.  I am not on 
the list, so please cc me with any replies, thanks!

-- 
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Gary Oberbrunner                garyo@genarts.com
GenArts, Inc.                   Tel: 617-492-2888
955 Mass. Ave                   Fax: 617-492-2852
Cambridge, MA 02139 USA         www.genarts.com