bug#14411: 24.3.50; compile.el: Better file search for parallel builds

[David Engster]

When doing parallel builds using GNU Make, jumping to the location of a
warning/error from the compilation buffer often does not work. This is
because GNU Make enters different directories at the same time, and the
resulting output is intermixed. The attached patch fixes this by looking
at all directories which were entered up to the point of the
warning/error, instead of just taking the directly preceding one. I'm
aware that this is not a perfect solution, since those directories might
contain files with identical names, in which case Emacs might show the
wrong one, but IMO it's still an improvement over the current
situation. This feature can also be disabled through a new variable.

-David

=== modified file 'lisp/progmodes/compile.el'
--- lisp/progmodes/compile.el   2013-04-24 13:50:22 +0000
+++ lisp/progmodes/compile.el   2013-05-16 18:49:35 +0000
@@ -611,6 +611,18 @@
                         (string :tag "Directory")))
   :group 'compilation)
 
+(defcustom compilation-search-all-directories t
+  "Whether further upward directories should be used when searching a file.
+When doing a parallel build, several files from different
+directories can be compiled at the same time.  This makes it
+difficult to determine the base directory for a relative file
+name in a compiler error or warning.  If this variable is
+non-nil, instead of just relying on the previous directory change
+in the compilation buffer, all other directories further upwards
+will be used as well."
+  :type 'boolean
+  :group 'compilation)
+
 ;;;###autoload
 (defcustom compile-command (purecopy "make -k ")
   "Last shell command used to do a compilation; default for next compilation.
@@ -2616,6 +2628,25 @@
                           (find-file-noselect name))
               fmts (cdr fmts)))
       (setq dirs (cdr dirs)))
+    ;; If we haven't found it, this might be a parallel build.
+    ;; Search the directories further up the buffer.
+    (when (and (null buffer)
+               compilation-search-all-directories)
+      (with-current-buffer (marker-buffer marker)
+        (save-excursion
+          (goto-char (marker-position marker))
+          (goto-char (compilation--previous-directory (point)))
+          (setq dirs (cdr (or (get-text-property (1- (point)) 
'compilation-directory)
+                              (get-text-property (point) 
'compilation-directory))))))
+      (while (and dirs (null buffer))
+        (setq thisdir (car dirs)
+              fmts formats)
+        (while (and fmts (null buffer))
+          (setq name (expand-file-name (format (car fmts) filename) thisdir)
+                buffer (and (file-exists-p name)
+                            (find-file-noselect name))
+                fmts (cdr fmts)))
+        (setq dirs (cdr dirs))))
     (while (null buffer)    ;Repeat until the user selects an existing file.
       ;; The file doesn't exist.  Ask the user where to find it.
       (save-excursion            ;This save-excursion is probably not right.