* bug#49197: [PATCH] 28.0.50; Inability to find "diff" prevents `font-lock-add-keywords' from working in `diff-mode'
@ 2021-06-23 21:00 Jim Porter
2021-06-24 16:07 ` Lars Ingebrigtsen
0 siblings, 1 reply; 2+ messages in thread
From: Jim Porter @ 2021-06-23 21:00 UTC (permalink / raw)
To: 49197
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This is a very minor issue that I happened to stumble upon. On systems
without "diff", adding a new font-lock rule via
`font-lock-add-keywords' doesn't do anything. This is (if I'm
understanding things correctly) because the diff-refined code will
signal an error, terminating the font-lock code early. Since
`diff--font-lock-refined' is normally the last element in the list,
this only causes issues when a user has added more font-lock rules. To
see the problem in action, you can do the following:
emacs -Q
(setq diff-command "nonexist")
(add-hook 'diff-mode-hook
(lambda ()
(font-lock-add-keywords
nil
'(("^..*?\\([[:blank:]]+\\)$" 1
'trailing-whitespace prepend))
t)))
C-x C-f diff-trailing-ws.patch ;; Attached
;; The added line should be highlighted with `trailing-whitespace',
;; but it isn't.
I've attached a patch for this which ignores `file-missing' errors
when using diff-refined during font-locking. With the patch, running
the above steps correctly highlights trailing whitespace.
[-- Attachment #2: 0001-Ignore-file-missing-errors-during-diff-refined-font-.patch --]
[-- Type: application/octet-stream, Size: 1978 bytes --]
From 5154533da7af1e07d1ce2630cbae5c4892eeb449 Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Wed, 23 Jun 2021 13:52:54 -0700
Subject: [PATCH] Ignore file-missing errors during diff-refined font-locking
* lisp/vc/diff-mode.el (diff--font-lock-refined): Ignore file-missing
errors.
---
lisp/vc/diff-mode.el | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index a0093391c6..4652afa1f9 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2265,17 +2265,20 @@ diff--font-lock-refined
;; same hunk.
(goto-char (next-single-char-property-change
(point) 'diff--font-lock-refined nil max)))
- (diff--iterate-hunks
- max
- (lambda (beg end)
- (unless (get-char-property beg 'diff--font-lock-refined)
- (diff--refine-hunk beg end)
- (let ((ol (make-overlay beg end)))
- (overlay-put ol 'diff--font-lock-refined t)
- (overlay-put ol 'diff-mode 'fine)
- (overlay-put ol 'evaporate t)
- (overlay-put ol 'modification-hooks
- '(diff--overlay-auto-delete))))))))
+ ;; Ignore errors that diff cannot be found so that custom font-lock
+ ;; keywords after `diff--font-lock-refined' can still be evaluated.
+ (ignore-error file-missing
+ (diff--iterate-hunks
+ max
+ (lambda (beg end)
+ (unless (get-char-property beg 'diff--font-lock-refined)
+ (diff--refine-hunk beg end)
+ (let ((ol (make-overlay beg end)))
+ (overlay-put ol 'diff--font-lock-refined t)
+ (overlay-put ol 'diff-mode 'fine)
+ (overlay-put ol 'evaporate t)
+ (overlay-put ol 'modification-hooks
+ '(diff--overlay-auto-delete)))))))))
(defun diff--overlay-auto-delete (ol _after _beg _end &optional _len)
(delete-overlay ol))
--
2.25.1
[-- Attachment #3: diff-trailing-ws.patch --]
[-- Type: application/octet-stream, Size: 123 bytes --]
--- pre.txt 2021-06-23 13:40:48.850659087 -0700
+++ post.txt 2021-06-23 13:40:53.942533907 -0700
@@ -1 +1 @@
-text
+text
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2021-06-23 21:00 bug#49197: [PATCH] 28.0.50; Inability to find "diff" prevents `font-lock-add-keywords' from working in `diff-mode' Jim Porter
2021-06-24 16:07 ` Lars Ingebrigtsen
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