vim-patch:9.1.1753: defaults: 'diffopt' option value can be improved (#35727)

Problem:  defaults: 'diffopt' option value can be improved
Solution: Update diffopt defaults to include "indent-heuristic" and
          "inline:char" (Yee Cheng Chin)

The default diff options have not been updated much despite new
functionality having been added to Vim.

- indent-heurstic: This has been enabled by default in Git since
  33de716387 in 2017. Given that Vim uses xdiff from Git, it makes sense
  to track the default configuration from Git.

- inline:char: This turns on character-wise inline highlighting which is
  generally much better than the default inline:simple. It has been
  implemented since vim/vim#16881 and we have not seen reports of any issues
  with it, and it has received good feedbacks.

closes: vim/vim#18255

976b365305

Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>

runtime/doc/news.txt

@@ -160,6 +160,7 @@ BUILD
 
 DEFAULTS
 
+• 'diffopt' default value now includes "indent-heuristic" and "inline:char".
 • 'statusline' default is exposed as a statusline expression (previously it
   was implemented as an internal C routine).
 • 'statusline' includes |vim.diagnostic.status()|

runtime/doc/options.txt

@@ -2182,7 +2182,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	security reasons.
 
 						*'diffopt'* *'dip'*
-'diffopt' 'dip'		string	(default "internal,filler,closeoff,inline:simple,linematch:40")
+'diffopt' 'dip'		string	(default "internal,filler,closeoff,indent-heuristic,inline:char,linematch:40")
 			global
 	Option settings for diff mode.  It can consist of the following items.
 	All are optional.  Items must be separated by a comma.

runtime/lua/vim/_meta/options.lua

@@ -1936,7 +1936,7 @@ vim.go.dex = vim.go.diffexpr
 ---
 ---
 --- @type string
-vim.o.diffopt = "internal,filler,closeoff,inline:simple,linematch:40"
+vim.o.diffopt = "internal,filler,closeoff,indent-heuristic,inline:char,linematch:40"
 vim.o.dip = vim.o.diffopt
 vim.go.diffopt = vim.o.diffopt
 vim.go.dip = vim.go.diffopt

src/nvim/diff.c

@@ -95,9 +95,10 @@ static bool diff_need_update = false;  // ex_diffupdate needs to be called
 #define ALL_WHITE_DIFF (DIFF_IWHITE | DIFF_IWHITEALL | DIFF_IWHITEEOL)
 #define ALL_INLINE (DIFF_INLINE_NONE | DIFF_INLINE_SIMPLE | DIFF_INLINE_CHAR | DIFF_INLINE_WORD)
 #define ALL_INLINE_DIFF (DIFF_INLINE_CHAR | DIFF_INLINE_WORD)
-static int diff_flags = DIFF_INTERNAL | DIFF_FILLER | DIFF_CLOSE_OFF | DIFF_LINEMATCH;
+static int diff_flags = DIFF_INTERNAL | DIFF_FILLER | DIFF_CLOSE_OFF
+                        | DIFF_LINEMATCH | DIFF_INLINE_CHAR;
 
-static int diff_algorithm = 0;
+static int diff_algorithm = XDF_INDENT_HEURISTIC;
 static int linematch_lines = 40;
 
 #define LBUFLEN 50               // length of line in diff file

src/nvim/options.lua

@@ -2374,7 +2374,7 @@ local options = {
     {
       abbreviation = 'dip',
       cb = 'did_set_diffopt',
-      defaults = 'internal,filler,closeoff,inline:simple,linematch:40',
+      defaults = 'internal,filler,closeoff,indent-heuristic,inline:char,linematch:40',
       -- Keep this in sync with diffopt_changed().
       values = {
         'filler',

test/functional/ui/diff_spec.lua

@@ -1249,7 +1249,7 @@ end)
 it('diff updates line numbers below filler lines', function()
   local screen = Screen.new(40, 14)
   exec([[
-    set diffopt=internal,filler,closeoff
+    set diffopt=internal,filler
     call setline(1, ['a', 'a', 'a', 'y', 'b', 'b', 'b', 'b', 'b'])
     vnew
     call setline(1, ['a', 'a', 'a', 'x', 'x', 'x', 'b', 'b', 'b', 'b', 'b'])

test/functional/ui/highlight_spec.lua

@@ -1220,7 +1220,7 @@ describe('CursorLine and CursorLineNr highlights', function()
     command('windo diffthis')
     screen:expect([[
       {7:  }{9:line 1 some text       }│{7:  }{9:^line 1 some text      }|
-      {7:  }{4:line 2 mo}{27:Re text!}{4:      }│{7:  }{4:line 2 mo}{27:re text}{4:      }|
+      {7:  }{4:line 2 mo}{27:R}{4:e text}{27:!}{4:      }│{7:  }{4:line 2 mo}{27:r}{4:e text      }|
       {7:  }{22:extra line!            }│{7:  }{23:----------------------}|
       {7:  }extra line!            │{7:  }extra line!           |*2
       {7:  }last line ...          │{7:  }last line ...         |
@@ -1232,7 +1232,7 @@ describe('CursorLine and CursorLineNr highlights', function()
     feed('jjjjj')
     screen:expect([[
       {7:  }line 1 some text       │{7:  }line 1 some text      |
-      {7:  }{4:line 2 mo}{27:Re text!}{4:      }│{7:  }{4:line 2 mo}{27:re text}{4:      }|
+      {7:  }{4:line 2 mo}{27:R}{4:e text}{27:!}{4:      }│{7:  }{4:line 2 mo}{27:r}{4:e text      }|
       {7:  }{22:extra line!            }│{7:  }{23:----------------------}|
       {7:  }extra line!            │{7:  }extra line!           |*2
       {7:  }last line ...          │{7:  }last line ...         |
@@ -1248,7 +1248,7 @@ describe('CursorLine and CursorLineNr highlights', function()
     feed('kkkk')
     screen:expect([[
       {7:  }line 1 some text       │{7:  }line 1 some text      |
-      {7:  }{100:line 2 mo}{101:Re text!}{100:      }│{7:  }{100:^line 2 mo}{101:re text}{100:      }|
+      {7:  }{100:line 2 mo}{101:R}{100:e text}{101:!}{100:      }│{7:  }{100:^line 2 mo}{101:r}{100:e text      }|
       {7:  }{22:extra line!            }│{7:  }{23:----------------------}|
       {7:  }extra line!            │{7:  }extra line!           |*2
       {7:  }last line ...          │{7:  }last line ...         |

test/functional/ui/linematch_spec.lua

@@ -31,7 +31,7 @@ describe('Diff mode screen with 3 diffs open', function()
 
   before_each(function()
     clear()
-    feed(':set diffopt+=linematch:30<cr>')
+    feed(':set diffopt=internal,filler,linematch:30<cr>')
     feed(':e ' .. fname .. '<cr>')
     feed(':vnew ' .. fname_2 .. '<cr>')
     feed(':vnew ' .. fname_3 .. '<cr>')
@@ -218,7 +218,7 @@ describe('Diff mode screen with 2 diffs open', function()
 
   describe('setup a diff with 2 files and set linematch:30', function()
     before_each(function()
-      feed(':set diffopt+=linematch:30<cr>')
+      feed(':set diffopt=internal,filler,linematch:30<cr>')
       local f1 = [[
 
 common line
@@ -701,7 +701,7 @@ something
   end)
   describe('setup a diff with 2 files and set linematch:30', function()
     before_each(function()
-      feed(':set diffopt+=linematch:30<cr>')
+      feed(':set diffopt=internal,filler,linematch:30<cr>')
       local f1 = [[
 // abc d
 // d
@@ -731,7 +731,7 @@ d
   end)
   describe('setup a diff with 2 files and set linematch:30, with ignore white', function()
     before_each(function()
-      feed(':set diffopt+=linematch:30<cr>:set diffopt+=iwhiteall<cr>')
+      feed(':set diffopt=internal,filler,linematch:30,iwhiteall<cr>')
       local f1 = [[
 void testFunction () {
   for (int i = 0; i < 10; i++) {
@@ -767,7 +767,7 @@ void testFunction () {
   end)
   describe('a diff that would result in multiple groups before grouping optimization', function()
     before_each(function()
-      feed(':set diffopt+=linematch:30<cr>')
+      feed(':set diffopt=internal,filler,linematch:30<cr>')
       local f1 = [[
 !A
 !B
@@ -806,7 +806,7 @@ void testFunction () {
   end)
   describe('a diff that would result in multiple groups before grouping optimization', function()
     before_each(function()
-      feed(':set diffopt+=linematch:30<cr>')
+      feed(':set diffopt=internal,filler,linematch:30<cr>')
       local f1 = [[
 !A
 !B
@@ -845,7 +845,7 @@ void testFunction () {
   end)
   describe('setup a diff with 2 files and set linematch:10', function()
     before_each(function()
-      feed(':set diffopt+=linematch:10<cr>')
+      feed(':set diffopt=internal,filler,linematch:10<cr>')
       local f1 = [[
 common line
 HIL
@@ -1024,7 +1024,7 @@ describe('regressions', function()
 
   it("doesn't crash with long lines", function()
     clear()
-    feed(':set diffopt+=linematch:30<cr>')
+    feed(':set diffopt=internal.filler,linematch:30<cr>')
     screen = Screen.new(100, 20)
     -- line must be greater than MATCH_CHAR_MAX_LEN
     n.api.nvim_buf_set_lines(0, 0, -1, false, { string.rep('a', 1000) .. 'hello' })
@@ -1035,7 +1035,7 @@ describe('regressions', function()
 
   it('properly computes filler lines for hunks bigger than linematch limit', function()
     clear()
-    feed(':set diffopt+=linematch:10<cr>')
+    feed(':set diffopt=internal,filler,linematch:10<cr>')
     screen = Screen.new(100, 20)
     local lines = {}
     for i = 0, 29 do
@@ -1093,7 +1093,7 @@ describe('regressions', function()
     n.exec('rightbelow vnew')
     n.api.nvim_buf_set_lines(0, 0, -1, false, { 'hijklm', 'nopqr', 'stuv' })
     n.exec([[
-      set diffopt+=linematch:60
+      set diffopt=internal,filler,linematch:60
       windo diffthis | wincmd t
       call feedkeys("Aq\<esc>")
       call feedkeys("GAklm\<esc>")

test/old/testdir/setup.vim

@@ -6,7 +6,7 @@ if exists('s:did_load')
     set completeopt=menu,preview
   endif
   set define=^\\s*#\\s*define
-  set diffopt=internal,filler,closeoff,inline:simple
+  set diffopt=internal,filler,closeoff,indent-heuristic,inline:char
   set directory^=.
   set display=
   set fillchars=vert:\|,foldsep:\|,fold:-

test/old/testdir/test_diffmode.vim

@@ -850,6 +850,7 @@ func Test_diff_nomodifiable()
 endfunc
 
 func Test_diff_hlID()
+  set diffopt=internal,filler
   new
   call setline(1, [1, 2, 3, 'Yz', 'a dxxg',])
   diffthis
@@ -892,6 +893,7 @@ func Test_diff_hlID()
   call assert_equal(synIDattr(diff_hlID(3, 1), "name"), "")
 
   %bwipe!
+  set diffopt&
 endfunc
 
 func Test_diff_filler()
@@ -1060,18 +1062,18 @@ func Test_diff_screen()
   call term_sendkeys(buf, ":set diffopt+=algorithm:histogram\<cr>")
   call VerifyScreenDump(buf, 'Test_diff_09', {})
 
-  " Test 10-11: normal/indent-heuristic
+  " Test 10-11: with/without indent-heuristic
   call term_sendkeys(buf, ":set diffopt&vim\<cr>")
   call WriteDiffFiles(buf, ['', '  def finalize(values)', '', '    values.each do |v|', '      v.finalize', '    end'],
       \ ['', '  def finalize(values)', '', '    values.each do |v|', '      v.prepare', '    end', '',
       \ '    values.each do |v|', '      v.finalize', '    end'])
   call term_sendkeys(buf, ":diffupdate!\<cr>")
-  call term_sendkeys(buf, ":set diffopt+=internal\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=internal\<cr>:\<cr>")
-  call VerifyScreenDump(buf, 'Test_diff_10', {})
+  call VerifyScreenDump(buf, 'Test_diff_11', {})
 
   " Leave trailing : at commandline!
-  call term_sendkeys(buf, ":set diffopt+=indent-heuristic\<cr>:\<cr>")
+  call term_sendkeys(buf, ":set diffopt-=indent-heuristic\<cr>:\<cr>")
-  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'one')
+  call VerifyScreenDump(buf, 'Test_diff_10', {}, 'one')
   " shouldn't matter, if indent-algorithm comes before or after the algorithm
   call term_sendkeys(buf, ":set diffopt&\<cr>")
   call term_sendkeys(buf, ":set diffopt+=indent-heuristic,algorithm:patience\<cr>:\<cr>")
@@ -1312,6 +1314,7 @@ func Test_diff_with_syntax()
   call writefile(lines, 'Xprogram2.c', 'D')
 
   let lines =<< trim END
+    set diffopt=internal,filler
 	edit Xprogram1.c
 	diffsplit Xprogram2.c
   END
@@ -1454,9 +1457,7 @@ func Test_diff_rnu()
   CheckScreendump
 
   let content =<< trim END
-    call setline(1, ['a', 'a', 'a', 'y', 'b', 'b', 'b', 'b', 'b'])
+    set diffopt=internal,filler
-    vnew
-    call setline(1, ['a', 'a', 'a', 'x', 'x', 'x', 'b', 'b', 'b', 'b', 'b'])
     call setline(1, ['a', 'a', 'a', 'y', 'b', 'b', 'b', 'b', 'b'])
     vnew
     call setline(1, ['a', 'a', 'a', 'x', 'x', 'x', 'b', 'b', 'b', 'b', 'b'])
@@ -1544,6 +1545,7 @@ endfunc
 " Test for adding/removing lines inside diff chunks, between diff chunks
 " and before diff chunks
 func Test_diff_modify_chunks()
+  set diffopt=internal,filler
   enew!
   let w2_id = win_getid()
   call setline(1, ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i'])
@@ -1623,6 +1625,7 @@ func Test_diff_modify_chunks()
   call assert_equal(['', '', '', '', '', '', '', '', ''], hl)
 
   %bw!
+  set diffopt&
 endfunc
 
 func Test_diff_binary()
@@ -2616,7 +2619,7 @@ func Test_linematch_diff()
   call delete('.Xdifile2.swp')
   call WriteDiffFiles(0, [], [])
   let buf = RunVimInTerminal('-d Xdifile1 Xdifile2', {})
-  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
+  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
 
   " enable linematch
   call term_sendkeys(buf, ":set diffopt=internal,filler,linematch:30\<CR>")
@@ -2644,7 +2647,7 @@ func Test_linematch_diff_iwhite()
   call delete('.Xdifile2.swp')
   call WriteDiffFiles(0, [], [])
   let buf = RunVimInTerminal('-d Xdifile1 Xdifile2', {})
-  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
+  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
 
   " setup a diff with 2 files and set linematch:30, with ignore white
   call term_sendkeys(buf, ":set diffopt=internal,filler,linematch:30\<CR>")
@@ -2671,7 +2674,7 @@ func Test_linematch_diff_grouping()
   call delete('.Xdifile2.swp')
   call WriteDiffFiles(0, [], [])
   let buf = RunVimInTerminal('-d Xdifile1 Xdifile2', {})
-  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
+  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
 
   " a diff that would result in multiple groups before grouping optimization
   call term_sendkeys(buf, ":set diffopt=internal,filler,linematch:30\<CR>")
@@ -2709,7 +2712,7 @@ func Test_linematch_diff_scroll()
   call delete('.Xdifile2.swp')
   call WriteDiffFiles(0, [], [])
   let buf = RunVimInTerminal('-d Xdifile1 Xdifile2', {})
-  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
+  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
 
   " a diff that would result in multiple groups before grouping optimization
   call term_sendkeys(buf, ":set diffopt=internal,filler,linematch:30\<CR>")
@@ -2740,7 +2743,7 @@ func Test_linematch_line_limit_exceeded()
   call delete('.Xdifile1.swp')
   call delete('.Xdifile2.swp')
   call WriteDiffFiles(0, [], [])
-  let buf = RunVimInTerminal('-d Xdifile1 Xdifile2', {})
+  let buf = RunVimInTerminal('-d Xdifile1 Xdifile2', {})
   call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
 
   call term_sendkeys(buf, ":set diffopt=internal,filler,linematch:10\<CR>")
@@ -2792,7 +2795,7 @@ func Test_linematch_3diffs()
   call delete('.Xdifile3.swp')
   call WriteDiffFiles3(0, [], [], [])
   let buf = RunVimInTerminal('-d Xdifile1 Xdifile2 Xdifile3', {})
-  call term_sendkeys(buf, "1\<c-w>w:set autoread\<CR>")
+  call term_sendkeys(buf, "1\<c-w>w:set autoread\<CR>")
   call term_sendkeys(buf, "2\<c-w>w:set autoread\<CR>")
   call term_sendkeys(buf, "3\<c-w>w:set autoread\<CR>")
   call term_sendkeys(buf, ":set diffopt=internal,filler,linematch:30\<CR>")
@@ -2827,7 +2830,7 @@ func Test_linematch_3diffs_sanity_check()
 func Test_linematch_3diffs_sanity_check()
   CheckScreendump
   call delete('.Xfile_linematch1.swp')
-  call delete('.Xfile_linematch2.swp')
+  call delete('.Xfile_linematch2.swp')
   call delete('.Xfile_linematch3.swp')
   let lines =<< trim END
     set diffopt=internal,filler,linematch:60

test/old/testdir/test_scroll_opt.vim

@@ -302,11 +302,43 @@ func Test_smoothscroll_diff_mode()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_smoothscroll_diff_change_line_default()
+  CheckScreendump
+
+  " Uses the new diffopt default with indent-heuristic and inline:char
+  let lines =<< trim END
+    set diffopt=internal,filler,closeoff,indent-heuristic,inline:char,followwrap smoothscroll
+    call setline(1, repeat(' abc', &columns))
+    call setline(2, 'bar')
+    call setline(3, repeat(' abc', &columns))
+    vnew
+    call setline(1, repeat(' abc', &columns))
+    call setline(2, 'foo')
+    call setline(3, 'bar')
+    call setline(4, repeat(' abc', &columns))
+    windo exe "normal! 2gg5\<C-E>"
+    windo diffthis
+  END
+  call writefile(lines, 'XSmoothDiffChangeLine', 'D')
+  let buf = RunVimInTerminal('-S XSmoothDiffChangeLine', #{rows: 20, columns: 55})
+
+  call VerifyScreenDump(buf, 'Test_smooth_diff_change_line_1', {})
+  call term_sendkeys(buf, "Abar")
+  call VerifyScreenDump(buf, 'Test_smooth_diff_change_line_2', {})
+  call term_sendkeys(buf, "\<Esc>")
+  call VerifyScreenDump(buf, 'Test_smooth_diff_change_line_3a', {})
+  call term_sendkeys(buf, "yyp")
+  call VerifyScreenDump(buf, 'Test_smooth_diff_change_line_4', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_smoothscroll_diff_change_line()
   CheckScreendump
 
+  " Uses the old diffopt default
   let lines =<< trim END
-    set diffopt+=followwrap smoothscroll
+    set diffopt=internal,filler,closeoff,followwrap,inline:simple smoothscroll
     call setline(1, repeat(' abc', &columns))
     call setline(2, 'bar')
     call setline(3, repeat(' abc', &columns))