From 948360a1e2259eb279108b8e6a852d20373fe7f4 Mon Sep 17 00:00:00 2001
From: Tomas Nordin <tomasn@posteo.net>
Date: Sat, 15 Mar 2025 04:08:47 +0200
Subject: [PATCH] Teach diff-apply-hunk to handle hunks with empty context
* lisp/vc/diff-mode.el (diff-find-source-location):
Consider the case when there is no diff context above or below
edited lines. (bug#72556)
* test/lisp/vc/diff-mode-tests.el: Add tests for undoing hunks
from diffs with addtions only in the beginning or end of the
source file.
(cherry picked from commit 4980287e081d3efd29f64973938ca2a0575f521e)
---
lisp/vc/diff-mode.el | 8 +--
test/lisp/vc/diff-mode-tests.el | 96 +++++++++++++++++++++++++++++++++
2 files changed, 101 insertions(+), 3 deletions(-)
diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index 5db61b144b3..acdcb691ae9 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2048,9 +2048,11 @@ SWITCHED is non-nil if the patch is already applied."
(goto-char (point-min)) (forward-line (1- (string-to-number line)))
(let* ((orig-pos (point))
(switched nil)
- ;; FIXME: Check for case where both OLD and NEW are found.
- (pos (or (diff-find-text (car old))
- (progn (setq switched t) (diff-find-text (car new)))
+ (maybe-old (diff-find-text (car old)))
+ (maybe-new (diff-find-text (car new)))
+ (pos (or (and maybe-new maybe-old (null reverse) (setq switched t) maybe-new)
+ maybe-old
+ (progn (setq switched t) maybe-new)
(progn (setq switched nil)
(condition-case nil
(diff-find-approx-text (car old))
diff --git a/test/lisp/vc/diff-mode-tests.el b/test/lisp/vc/diff-mode-tests.el
index bbd66824e48..5611e9abc79 100644
--- a/test/lisp/vc/diff-mode-tests.el
+++ b/test/lisp/vc/diff-mode-tests.el
@@ -597,5 +597,101 @@ baz"))))
(should (eq (get-text-property (match-beginning 0) 'face)
'diff-context)))))
+(ert-deftest diff-mode-test-topmost-addition-undo ()
+ (let ((patch "diff --git a/fruits b/fruits
+index 0dcecd3..d0eb2e7 100644
+--- a/fruits
++++ b/fruits
+@@ -1,2 +1,3 @@
++fruits
+ apple
+ orange
+")
+ (text-before "apple
+orange
+")
+ (text-after "fruits
+apple
+orange
+"))
+ (ert-with-temp-directory temp-dir
+ (let ((buf-after
+ (find-file-noselect (format "%s/%s" temp-dir "fruits"))))
+ (cd temp-dir)
+
+ (with-current-buffer buf-after (insert text-after) (save-buffer))
+ (with-temp-buffer
+ (insert patch)
+ (goto-char (point-min))
+ (diff-hunk-next)
+ ;; Undo hunk by non-nil REVERSE argument (C-u C-c C-a)
+ (diff-apply-hunk t))
+ (with-current-buffer buf-after
+ (should (string-equal (buffer-string) text-before)))
+
+ (with-current-buffer buf-after
+ (erase-buffer) (insert text-after) (save-buffer))
+ (with-temp-buffer
+ (insert patch)
+ (goto-char (point-min))
+ (diff-hunk-next)
+ ;; Undo hunk by dwim behaviour
+ (cl-letf (((symbol-function 'y-or-n-p) #'always))
+ (diff-apply-hunk)))
+ (with-current-buffer buf-after
+ (should (string-equal (buffer-string) text-before)))
+
+ (with-current-buffer buf-after
+ (set-buffer-modified-p nil)
+ (kill-buffer buf-after))))))
+
+(ert-deftest diff-mode-test-bottommost-addition-undo ()
+ (let ((patch "diff --git a/fruits b/fruits
+index 0dcecd3..6f210ff 100644
+--- a/fruits
++++ b/fruits
+@@ -1,2 +1,3 @@
+ apple
+ orange
++plum
+")
+ (text-before "apple
+orange
+")
+ (text-after "apple
+orange
+plum
+"))
+ (ert-with-temp-directory temp-dir
+ (let ((buf-after
+ (find-file-noselect (format "%s/%s" temp-dir "fruits"))))
+ (cd temp-dir)
+
+ (with-current-buffer buf-after (insert text-after) (save-buffer))
+ (with-temp-buffer
+ (insert patch)
+ (goto-char (point-min))
+ (diff-hunk-next)
+ ;; Undo hunk by non-nil REVERSE argument (C-u C-c C-a)
+ (diff-apply-hunk t))
+ (with-current-buffer buf-after
+ (should (string-equal (buffer-string) text-before)))
+
+ (with-current-buffer buf-after
+ (erase-buffer) (insert text-after) (save-buffer))
+ (with-temp-buffer
+ (insert patch)
+ (goto-char (point-min))
+ (diff-hunk-next)
+ ;; Undo hunk by dwim behaviour
+ (cl-letf (((symbol-function 'y-or-n-p) #'always))
+ (diff-apply-hunk)))
+ (with-current-buffer buf-after
+ (should (string-equal (buffer-string) text-before)))
+
+ (with-current-buffer buf-after
+ (set-buffer-modified-p nil)
+ (kill-buffer buf-after))))))
+
(provide 'diff-mode-tests)
;;; diff-mode-tests.el ends here
--
2.39.5