Make OMake support slightly less expensive (bug#39595)

When run with -p or -P, OMake regurgitates error messages that
prevented further progress, indented by 6 spaces.  Use that fact
to ameliorate the modification done to other error message regexps.

* lisp/progmodes/compile.el (compilation-parse-errors):
When 'omake' is enabled, allow error messages to be indented by 0 or 6
spaces instead of any number of spaces, to avoid pathological
behaviour.
(compilation-error-regexp-alist-alist): Anchor the 'omake' pattern to
bol for performance.  Repair the 'ruby-Test::Unit' pattern, which
relied on the previously over-generous 'omake' hack.
* etc/compilation.txt (OMake): Add examples.
* test/lisp/progmodes/compile-tests.el (compile-tests--test-regexps-data)
(compile-test-error-regexps): Add test for OMake (indented error).

1 files changed, 16 insertions, 0 deletions

diff --git a/etc/compilation.txt b/etc/compilation.txt
index c465b4b94aa..ebce6a14d06 100644
--- a/etc/compilation.txt
+++ b/etc/compilation.txt
@@ -384,6 +384,22 @@ symbol: watcom
 ..\src\ctrl\lister.c(120): Warning! W201: Unreachable code
 
 
+* OMake
+
+symbol: omake
+
+When using in -p or -P mode, OMake will detect changes to files and
+report critical build errors indented by 6 spaces.
+
+*** omake: file alpha.c changed
+*** omake: targets were not rebuilt because of errors:
+   alpha.o
+      depends on: alpha.c
+      - build . alpha.o
+      + cc -I. -c -o alpha.o alpha.c
+      alpha.c:5:15: error: expected ';' after expression
+
+
 * Oracle pro*c
 
 symbol: oracle