bug#9226: 23.3; [rgrep]; (matches found) ?

[Juri Linkov <juri@jurta.org>]

> Sounds like an improvement to me.

This patch below fixes the case you reported and also the case of
"find | xargs grep" because it checks the value of buffer-modified
set in `compilation-start', whereas empty output doesn't change it.
It still relies on unreliable heuristics, but I carefully tested it with
all known test cases and it displays correct messages in all of them.
Running grep on the dir with a file containing "test", I get the following
results (command and exit status message):

grep -inH -e "test" *
Grep finished (matches found)

grep -inH -e "testx" *
Grep finished with no matches found

grepx -inH -e "test" *
Grep exited abnormally with code 127

find . -exec grep -i test {} \;
Grep finished (matches found)

find . -exec grep -i testx {} \;
Grep finished with no matches found

find . -name testx -exec grep -i testx {} \;
Grep finished with no matches found

find . -print0 | xargs -0 -e grep -i -nH -e test
Grep finished (matches found)

find . -print0 | xargs -0 -e grep -i -nH -e testx
Grep finished with no matches found

=== modified file 'lisp/progmodes/grep.el'
--- lisp/progmodes/grep.el	2011-08-10 20:31:17 +0000
+++ lisp/progmodes/grep.el	2011-08-17 16:47:24 +0000
@@ -463,9 +463,9 @@ (defun grep-process-setup ()
   (set (make-local-variable 'compilation-exit-message-function)
        (lambda (status code msg)
 	 (if (eq status 'exit)
-	     (cond ((zerop code)
+	     (cond ((and (zerop code) (buffer-modified-p))
 		    '("finished (matches found)\n" . "matched"))
-		   ((= code 1)
+		   ((or (= code 1) (not (buffer-modified-p)))
 		    '("finished with no matches found\n" . "no match"))
 		   (t
 		    (cons msg code)))