Set the compilation-error-regexp-alist in a hook (#126)

Some modes, for instance verilog-mode, adds to the
compilation-error-regexp-alist and friends which could interfere with
rg-mode regexps. Since rg-mode isn't a generic compilation mode we
want to avoid that.
This solution defer setting these regexps to the last run
compilation-mode-hook to be able to override whatever happens in other
hooks.

rg-result.el

@@ -507,6 +507,19 @@ This function is called from `compilation-filter-hook'."
       (when (re-search-backward "^File: \\(.*\\)$" (point-min) t)
         (list (match-string 1))))))
 
+(defun rg-set-compilation-error-regexps ()
+  "Set the compilation mode regexps for errors for rg-mode buffers."
+  (set (make-local-variable 'compilation-error-regexp-alist)
+       '(rg-group-with-column
+         rg-nogroup-with-column
+         rg-group-no-column
+         rg-nogroup-no-column))
+  (set (make-local-variable 'compilation-error-regexp-alist-alist)
+       (list (cons 'rg-nogroup-no-column (list rg-file-line-pattern-nogroup 1 2))
+             (cons 'rg-nogroup-with-column (list rg-file-line-column-pattern-nogroup 1 2 3))
+             (cons 'rg-group-with-column (list (rg-file-line-column-pattern-group) 'rg-match-grouped-filename 1 2))
+             (cons 'rg-group-no-column (list (rg-file-line-pattern-group) 'rg-match-grouped-filename 1)))))
+
 (define-compilation-mode rg-mode "rg"
   "Major mode for `rg' search results.
 Commands:
@@ -528,14 +541,6 @@ Commands:
   (set (make-local-variable 'compilation-line-face) 'rg-line-number-face)
   (set (make-local-variable 'compilation-column-face) 'rg-column-number-face)
 
-  (set (make-local-variable 'compilation-error-regexp-alist)
-       '(rg-group-with-column rg-nogroup-with-column rg-group-no-column  rg-nogroup-no-column))
-  (set (make-local-variable 'compilation-error-regexp-alist-alist)
-       (list (cons 'rg-nogroup-no-column (list rg-file-line-pattern-nogroup 1 2))
-             (cons 'rg-nogroup-with-column (list rg-file-line-column-pattern-nogroup 1 2 3))
-             (cons 'rg-group-with-column (list (rg-file-line-column-pattern-group) 'rg-match-grouped-filename 1 2))
-             (cons 'rg-group-no-column (list (rg-file-line-pattern-group) 'rg-match-grouped-filename 1))))
-
   ;; compilation-directory-matcher can't be nil, so we set it to a regexp that
   ;; can never match.
   (set (make-local-variable 'compilation-directory-matcher) '("\\`a\\`"))
@@ -545,7 +550,11 @@ Commands:
   (set (make-local-variable 'compilation-error-screen-columns) nil)
   (unless rg-search-history
     (setq rg-search-history (rg-history-create)))
-  (set (make-local-variable 'compilation-filter-hook) '(rg-filter)))
+  (set (make-local-variable 'compilation-filter-hook) '(rg-filter))
+  ;; Set compilation error regexps as the last compilation-mode-hook to be
+  ;; able to override these if they were set by other hooks.
+  (add-hook 'compilation-mode-hook
+            'rg-set-compilation-error-regexps 90 'local))
 
 (defun rg-maybe-show-header ()
   "Recreate header if enabled."

test/rg.el-test.el

@@ -974,6 +974,35 @@ and ungrouped otherwise."
     (should (equal (expand-file-name called-dir) project-dir))
     (should (eq called-literal nil))))
 
+
+(defun rg-only-rg-regexps-p ()
+  (and (seq-every-p
+        (lambda (elem) (eq elem t))
+        (mapcar (lambda (regexp)
+                  (s-starts-with-p "rg-" (symbol-name regexp)))
+                compilation-error-regexp-alist))
+       (seq-every-p
+        (lambda (elem) (eq elem t))
+        (mapcar (lambda (pair)
+                  (s-starts-with-p "rg-" (symbol-name (car pair))))
+                compilation-error-regexp-alist-alist))))
+
+(ert-deftest rg-integration/compilation-error-regexp ()
+  "Test that compilation-error-regexp-alist is only using rg regexps."
+  (with-temp-buffer
+    (rg-mode)
+    (should (rg-only-rg-regexps-p)))
+  (with-temp-buffer
+    (setq compilation-error-regexp-alist '(foo-bar))
+    (rg-mode)
+    (should (rg-only-rg-regexps-p)))
+  (with-temp-buffer
+    (add-hook 'compilation-mode-hook
+              (lambda ()
+                (setq compilation-error-regexp-alist '(foo-bar))))
+    (rg-mode)
+    (should (rg-only-rg-regexps-p))))
+
 (provide 'rg.el-test)
 
 ;;; rg.el-test.el ends here