vim-patch:8.2.3925: diff mode confused by NUL bytes (#18033)

Problem:    Diff mode confused by NUL bytes.
Solution:   Handle NUL bytes differently. (Christian Brabandt, closes vim/vim#9421,
            closes vim/vim#9418)
https://github.com/vim/vim/commit/06f6095623cfcc72da08748c058d13b465652fd4

2 files changed, 47 insertions, 4 deletions

diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index a6bbe40999..0b55fb877c 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -743,11 +743,16 @@ static int diff_write_buffer(buf_T *buf, diffin_T *din)
   for (linenr_T lnum = 1; lnum <= buf->b_ml.ml_line_count; lnum++) {
     for (char_u *s = ml_get_buf(buf, lnum, false); *s != NUL;) {
       if (diff_flags & DIFF_ICASE) {
+        int c;
         char_u cbuf[MB_MAXBYTES + 1];
 
-        // xdiff doesn't support ignoring case, fold-case the text.
-        int c = utf_ptr2char(s);
-        c = utf_fold(c);
+        if (*s == NL) {
+          c = NUL;
+        } else {
+          // xdiff doesn't support ignoring case, fold-case the text.
+          c = utf_ptr2char(s);
+          c = utf_fold(c);
+        }
         const int orig_len = utfc_ptr2len(s);
         if (utf_char2bytes(c, cbuf) != orig_len) {
           // TODO(Bram): handle byte length difference
@@ -759,7 +764,8 @@ static int diff_write_buffer(buf_T *buf, diffin_T *din)
         s += orig_len;
         len += orig_len;
       } else {
-        ptr[len++] = *s++;
+        ptr[len++] = *s == NL ? NUL : *s;
+        s++;
       }
     }
     ptr[len++] = NL;
diff --git a/src/nvim/testdir/test_diffmode.vim b/src/nvim/testdir/test_diffmode.vim
index 10eb979b45..be9a77ee75 100644
--- a/src/nvim/testdir/test_diffmode.vim
+++ b/src/nvim/testdir/test_diffmode.vim
@@ -1295,4 +1295,41 @@ func Test_diff_filler_cursorcolumn()
 endfunc
 
 
+func Test_diff_binary()
+  CheckScreendump
+
+  let content =<< trim END
+    call setline(1, ['a', 'b', "c\n", 'd', 'e', 'f', 'g'])
+    vnew
+    call setline(1, ['A', 'b', 'c', 'd', 'E', 'f', 'g'])
+    windo diffthis
+    wincmd p
+    norm! gg0
+    redraw!
+  END
+  call writefile(content, 'Xtest_diff_bin')
+  let buf = RunVimInTerminal('-S Xtest_diff_bin', {})
+
+  " Test using internal diff
+  call VerifyScreenDump(buf, 'Test_diff_bin_01', {})
+
+  " Test using internal diff and case folding
+  call term_sendkeys(buf, ":set diffopt+=icase\<cr>")
+  call term_sendkeys(buf, "\<C-l>")
+  call VerifyScreenDump(buf, 'Test_diff_bin_02', {})
+  " Test using external diff
+  call term_sendkeys(buf, ":set diffopt=filler\<cr>")
+  call term_sendkeys(buf, "\<C-l>")
+  call VerifyScreenDump(buf, 'Test_diff_bin_03', {})
+  " Test using external diff and case folding
+  call term_sendkeys(buf, ":set diffopt=filler,icase\<cr>")
+  call term_sendkeys(buf, "\<C-l>")
+  call VerifyScreenDump(buf, 'Test_diff_bin_04', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('Xtest_diff_bin')
+  set diffopt&vim
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab