Expand the file name match so that the match end can be used to limit path character substitution.

tools/emacs/trybot.el

 ; To use this,
 ; 1) Add to init.el:
 ;    (setq-default chrome-root "/path/to/chrome/src/")
 ;    (add-to-list 'load-path (concat chrome-root "tools/emacs"))
 ;    (require 'trybot)
 ; 2) Run on trybot output:
 ;    M-x trybot
 ;
 ; To hack on this,
 ; M-x eval-buffer
 ; M-x trybot-test
 
 (defvar chrome-root nil
   "Path to the src/ directory of your Chrome checkout.")
 
 (defun get-chrome-root ()
   (or chrome-root default-directory))
 
+; Hunt down from the top, case correcting each path component as needed.
+; Currently does not keep a cache.  Returns nil if no matching file can be
+; figured out.
+(defun case-corrected-filename (filename)
+  (save-match-data
+    (let ((path-components (split-string filename "/"))
+          (corrected-path (file-name-as-directory (get-chrome-root))))
+      (mapc
+       (function
+        (lambda (elt)
+          (if corrected-path
+              (let ((next-component
+                     (car (member-ignore-case
+                           elt (directory-files corrected-path)))))
+                (setq corrected-path
+                      (and next-component
+                           (file-name-as-directory
+                            (concat corrected-path next-component))))))))
+       path-components)
+      (if corrected-path
+          (file-relative-name (directory-file-name corrected-path)
+                              (get-chrome-root))
+        nil))))
+
 (defun trybot-fixup ()
   "Parse and fixup the contents of the current buffer as trybot output."
 
   ;; Fixup paths.
   (cd (get-chrome-root))
 
   ;; Delete Windows \r.
   (delete-trailing-whitespace)
 
   ;; Fix up path references.
   ; XXX is there something I should so so this stuff doesn't end up on the
   ; undo stack?
   (goto-char (point-min))
   ; Fix Windows paths ("d:\...\src\").
   ; TODO: need to fix case; e.g. third_party/webkit -> third_party/WebKit. :(
-  (while (re-search-forward "^.:\\\\.*\\\\src\\\\" nil t)
-    (replace-match "")
+  (while (re-search-forward "\\(^.:\\\\.*\\\\src\\\\\\)\\(.*?\\)[(:]" nil t)
+    (replace-match "" nil t nil 1)
     ; Line now looks like:
     ;  foo\bar\baz.cc error message here
     ; We want to fixup backslashes in path into forward slashes, without
-    ; modifying the error message.
-    ; XXX current eats backslashes after the filename; how can I limit it to
-    ; changing from current point up to the first space?
-    (subst-char-in-region (point) (line-end-position) ?\\ ?/))
+    ; modifying the error message - by matching up to the first colon above
+    ; (which will be just beyond the end of the filename) we can use the end of
+    ; the match as a limit.
+    (subst-char-in-region (point) (match-end 0) ?\\ ?/)
+    ; See if we can correct the file name casing.
+    (let ((filename (buffer-substring (match-beginning 2) (match-end 2))))
+      (if (and (not (file-exists-p filename))
+               (setq filename (case-corrected-filename filename)))
+          (replace-match filename t t nil 2))))
   (goto-char (point-min))
 
   ;; Switch into compilation mode.
   (compilation-mode))
 
 (defun trybot-test ()
   "Load our test data and do the trybot parse on it."
   (interactive)
 
   (switch-to-buffer (get-buffer-create "*trybot-test*"))
@@ skipping 17 matching lines @@
   ;; TODO: fixup URL to append /text if necessary.
 
   ;; Extract the body out of the URL.
   ; TODO: delete HTTP headers somehow.
   (switch-to-buffer (get-buffer-create "*trybot*"))
   (buffer-swap-text (url-retrieve-synchronously url))
 
   (trybot-fixup))
 
 (provide 'trybot)