patch 9.1.0740: incorrect internal diff with empty file

ynkdir · chrisbra · commit f1694b439bb1 · 2024-09-22T11:26:13.000+02:00
Problem:  incorrect internal diff with an empty file
Solution: Set pointer to NULL, instead of using an empty line file
          (Yukihiro Nakadaira)

When using internal diff, empty file is read as one empty line file.
So result differs from external diff.

closes: #15719

Signed-off-by: Yukihiro Nakadaira &lt;yukihiro.nakadaira@gmail.com&gt;
Signed-off-by: Christian Brabandt &lt;cb@256bit.org&gt;
diff --git a/src/diff.c b/src/diff.c
@@ -760,6 +760,13 @@ diff_write_buffer(buf_T *buf, diffin_T *din)
     long	len = 0;
     char_u	*ptr;
 
+    if (buf->b_ml.ml_flags & ML_EMPTY)
+    {
+	din->din_mmfile.ptr = NULL;
+	din->din_mmfile.size = 0;
+	return OK;
+    }
+
     // xdiff requires one big block of memory with all the text.
     for (lnum = 1; lnum <= buf->b_ml.ml_line_count; ++lnum)
 	len += ml_get_buf_len(buf, lnum) + 1;
diff --git a/src/testdir/dumps/Test_diff_21.dump b/src/testdir/dumps/Test_diff_21.dump
@@ -0,0 +1,20 @@
+| +0#0000e05#a8a8a8255@1|0+0#0000000#5fd7ff255| @33||+1&#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@34
+|~+0&#ffffff0| @35||+1#0000000&| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@34
+|~+0#4040ff13&| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|X+3#0000000&|d|i|f|i|l|e|1| @10|1|,|1| @11|A|l@1| |X+1&&|d|i|f|i|l|e|2| @10|0|,|0|-|1| @9|A|l@1
+|:+0&&> @73
diff --git a/src/testdir/dumps/Test_diff_22.dump b/src/testdir/dumps/Test_diff_22.dump
@@ -0,0 +1,20 @@
+| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@34||+1#0000000#ffffff0| +0#0000e05#a8a8a8255@1|0+0#0000000#5fd7ff255| @33
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@34||+1&&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|X+3#0000000&|d|i|f|i|l|e|1| @10|0|,|0|-|1| @9|A|l@1| |X+1&&|d|i|f|i|l|e|2| @10|1|,|1| @11|A|l@1
+|:+0&&> @73
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
@@ -1015,9 +1015,17 @@ func Test_diff_screen()
   call WriteDiffFiles(buf, ['a ', 'x', 'cd', 'ef', 'xx  xx', 'foo', 'bar'], ['a', 'x', 'c d', ' ef', 'xx xx', 'foo', '', 'bar'])
   call VerifyInternal(buf, 'Test_diff_19', " diffopt+=iwhiteeol")
 
-  " Test 19: test diffopt+=iwhiteall
+  " Test 20: test diffopt+=iwhiteall
   call VerifyInternal(buf, 'Test_diff_20', " diffopt+=iwhiteall")
 
+  " Test 21: Delete all lines
+  call WriteDiffFiles(buf, [0], [])
+  call VerifyBoth(buf, "Test_diff_21", "")
+
+  " Test 22: Add line to empty file
+  call WriteDiffFiles(buf, [], [0])
+  call VerifyBoth(buf, "Test_diff_22", "")
+
   " clean up
   call StopVimInTerminal(buf)
   call delete('Xdifile1')
diff --git a/src/version.c b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    740,
 /**/
     739,
 /**/
