tests: add test for hg-test-mode emacs code

This is just coverage for the compilation-mode support, but that was
enough of a hassle that I wanted to have it covered somehow. Test
methodology is _extremely_ cargo-culted from the test for
compilation-mode in emacs, so I still have no idea what I'm doing.

Differential Revision: https://phab.mercurial-scm.org/D6003

tests/test-contrib-emacs.t

@@ -0,0 +1,8 b''
+#require emacs
+  $ emacs -q -no-site-file -batch -l $TESTDIR/../contrib/hg-test-mode.el \
+  >  -f ert-run-tests-batch-and-exit
+  Running 1 tests (*) (glob)
+     passed  1/1  hg-test-mode--compilation-mode-support
+  
+  Ran 1 tests, 1 results as expected (*) (glob)
+  

contrib/hg-test-mode.el

@@ -1,68 +1,97 b''
 ;; hg-test-mode.el - Major mode for editing Mercurial tests
 ;;
 ;; Copyright 2014 Matt Mackall <[e-mail]>
 ;; "I have no idea what I'm doing"
 ;;
 ;; This software may be used and distributed according to the terms of the
 ;; GNU General Public License version 2 or any later version.
 ;;
 ;; To enable, add something like the following to your .emacs:
 ;;
 ;; (if (file-exists-p "~/hg/contrib/hg-test-mode.el")
 ;;    (load "~/hg/contrib/hg-test-mode.el"))
 
 (defvar hg-test-mode-hook nil)
 
 (defvar hg-test-mode-map
   (let ((map (make-keymap)))
     (define-key map "\C-j" 'newline-and-indent)
     map)
   "Keymap for hg test major mode")
 
 (add-to-list 'auto-mode-alist '("\\.t\\'" . hg-test-mode))
 
 (defconst hg-test-font-lock-keywords-1
   (list
    '("^  \\(\\$\\|>>>\\) " 1 font-lock-builtin-face)
    '("^  \\(>\\|\\.\\.\\.\\) " 1 font-lock-constant-face)
    '("^  \\([[][0-9]+[]]\\)$" 1 font-lock-warning-face)
    '("^  \\(.*?\\)\\(\\( [(][-a-z]+[)]\\)*\\)$" 1 font-lock-string-face)
    '("\\$?\\(HG\\|TEST\\)\\w+=?" . font-lock-variable-name-face)
    '("^  \\(.*?\\)\\(\\( [(][-a-z]+[)]\\)+\\)$" 2 font-lock-type-face)
    '("^#.*" . font-lock-preprocessor-face)
    '("^\\([^ ].*\\)$" 1 font-lock-comment-face)
    )
   "Minimal highlighting expressions for hg-test mode")
 
 (defvar hg-test-font-lock-keywords hg-test-font-lock-keywords-1
   "Default highlighting expressions for hg-test mode")
 
 (defvar hg-test-mode-syntax-table
   (let ((st (make-syntax-table)))
     (modify-syntax-entry ?\" "w" st) ;; disable standard quoting
     st)
 "Syntax table for hg-test mode")
 
 (defun hg-test-mode ()
   (interactive)
   (kill-all-local-variables)
   (use-local-map hg-test-mode-map)
   (set-syntax-table hg-test-mode-syntax-table)
   (set (make-local-variable 'font-lock-defaults) '(hg-test-font-lock-keywords))
   (setq major-mode 'hg-test-mode)
   (setq mode-name "hg-test")
   (run-hooks 'hg-test-mode-hook))
 
 (with-eval-after-load "compile"
   ;; Link to Python sources in tracebacks in .t failures.
   (add-to-list 'compilation-error-regexp-alist-alist
                '(hg-test-output-python-tb
                  "^\\+ +File ['\"]\\([^'\"]+\\)['\"], line \\([0-9]+\\)," 1 2))
   (add-to-list 'compilation-error-regexp-alist 'hg-test-output-python-tb)
   ;; Link to source files in test-check-code.t violations.
   (add-to-list 'compilation-error-regexp-alist-alist
                '(hg-test-check-code-output
                  "\\+  \\([^:\n]+\\):\\([0-9]+\\):$" 1 2))
   (add-to-list 'compilation-error-regexp-alist 'hg-test-check-code-output))
 
+(defun hg-test-mode--test-one-error-line-regexp (test)
+  (erase-buffer)
+  (setq compilation-locs (make-hash-table))
+  (insert (car test))
+  (compilation-parse-errors (point-min) (point-max))
+  (let ((msg (get-text-property 1 'compilation-message)))
+    (should msg)
+    (let ((loc (compilation--message->loc msg))
+          (line (nth 1 test))
+          (file (nth 2 test)))
+      (should (equal (compilation--loc->line loc) line))
+      (should (equal (caar (compilation--loc->file-struct loc)) file)))
+      msg))
+
+(require 'ert)
+(ert-deftest hg-test-mode--compilation-mode-support ()
+  "Test hg-specific compilation-mode regular expressions"
+  (require 'compile)
+  (with-temp-buffer
+    (font-lock-mode -1)
+    (mapc 'hg-test-mode--test-one-error-line-regexp
+          '(
+            ("+  contrib/debugshell.py:37:" 37 "contrib/debugshell.py")
+            ("+    File \"/tmp/hg/mercurial/commands.py\", line 3115, in help_"
+             3115 "/tmp/hg/mercurial/commands.py")
+            ("+    File \"mercurial/dispatch.py\", line 225, in dispatch"
+             225 "mercurial/dispatch.py")))))
+
+
 (provide 'hg-test-mode)