vim-patch:8.2.0064: diffmode completion doesn't use per-window setting

Problem:    Diffmode completion doesn't use per-window setting.
Solution:   Check if a window is in diff mode. (Dominique Pell, closes vim/vim#5419)
efcc329020

src/nvim/buffer.c

@@ -2309,6 +2309,10 @@ int ExpandBufnames(char_u *pat, int *num_file, char_u ***file, int options)
   *num_file = 0;                    // return values in case of FAIL
   *file = NULL;
 
+  if ((options & BUF_DIFF_FILTER) && !curwin->w_p_diff) {
+    return FAIL;
+  }
+
   // Make a copy of "pat" and change "^" to "\(^\|[\/]\)".
   if (*pat == '^') {
     patc = xmalloc(STRLEN(pat) + 11);
@@ -2348,9 +2352,7 @@ int ExpandBufnames(char_u *pat, int *num_file, char_u ***file, int options)
         if (options & BUF_DIFF_FILTER) {
           // Skip buffers not suitable for
           // :diffget or :diffput completion.
-          if (buf == curbuf
+          if (buf == curbuf || !diff_mode_buf(buf)) {
-              || !diff_mode_buf(curbuf)
-              || !diff_mode_buf(buf)) {
             continue;
           }
         }

src/nvim/testdir/test_diffmode.vim

@@ -242,43 +242,60 @@ func Test_diffput_two()
   bwipe! b
 endfunc
 
-func Test_diffget_diffput_completion()
-  new Xdiff1 | diffthis
-  new Xdiff2 | diffthis
-  new Xdiff3 | diffthis
-  new Xdiff4
-
 " :diffput and :diffget completes names of buffers which
 " are in diff mode and which are different then current buffer.
-  b Xdiff1
+" No completion when the current window is not in diff mode.
-  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+func Test_diffget_diffput_completion()
-  call assert_equal('"diffput Xdiff2 Xdiff3', @:)
+  e            Xdiff1 | diffthis
-  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  botright new Xdiff2
-  call assert_equal('"diffget Xdiff2 Xdiff3', @:)
+  botright new Xdiff3 | split | diffthis
-  call assert_equal(['Xdiff2', 'Xdiff3'], getcompletion('', 'diff_buffer'))
+  botright new Xdiff4 | diffthis
 
-  b Xdiff2
+  wincmd t
+  call assert_equal('Xdiff1', bufname('%'))
   call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_equal('"diffput Xdiff1 Xdiff3', @:)
+  call assert_equal('"diffput Xdiff3 Xdiff4', @:)
   call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_equal('"diffget Xdiff1 Xdiff3', @:)
+  call assert_equal('"diffget Xdiff3 Xdiff4', @:)
-  call assert_equal(['Xdiff1', 'Xdiff3'], getcompletion('', 'diff_buffer'))
+  call assert_equal(['Xdiff3', 'Xdiff4'], getcompletion('', 'diff_buffer'))
 
-  b Xdiff3
+  " Xdiff2 is not in diff mode, so no completion for :diffput, :diffget
-  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  wincmd j
-  call assert_equal('"diffput Xdiff1 Xdiff2', @:)
+  call assert_equal('Xdiff2', bufname('%'))
-  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_equal('"diffget Xdiff1 Xdiff2', @:)
-  call assert_equal(['Xdiff1', 'Xdiff2'], getcompletion('', 'diff_buffer'))
-
-  " No completion when in Xdiff4, it's not in diff mode.
-  b Xdiff4
   call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"diffput ', @:)
   call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"diffget ', @:)
   call assert_equal([], getcompletion('', 'diff_buffer'))
 
+  " Xdiff3 is split in 2 windows, only the top one is in diff mode.
+  " So completion of :diffput :diffget only happens in the top window.
+  wincmd j
+  call assert_equal('Xdiff3', bufname('%'))
+  call assert_equal(1, &diff)
+  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffput Xdiff1 Xdiff4', @:)
+  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffget Xdiff1 Xdiff4', @:)
+  call assert_equal(['Xdiff1', 'Xdiff4'], getcompletion('', 'diff_buffer'))
+
+  wincmd j
+  call assert_equal('Xdiff3', bufname('%'))
+  call assert_equal(0, &diff)
+  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffput ', @:)
+  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffget ', @:)
+  call assert_equal([], getcompletion('', 'diff_buffer'))
+
+  wincmd j
+  call assert_equal('Xdiff4', bufname('%'))
+  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffput Xdiff1 Xdiff3', @:)
+  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffget Xdiff1 Xdiff3', @:)
+  call assert_equal(['Xdiff1', 'Xdiff3'], getcompletion('', 'diff_buffer'))
+
   %bwipe
 endfunc