vim-patch:8.2.2518: 'listchars' should be window-local

Problem:    'listchars' should be window-local.
Solution:   Make 'listchars' global-local. (Yegappan Lakshmanan, Marco Hinz,
            closes vim/vim#5206, closes vim/vim#7850)
eed9d46293

Nvim already has this feature, but it implements :set listchars the same
as :setglobal listchars, which is incorrect. Vim's implementation of
:set listchars is correct: using :set listchars clears local value.

src/nvim/option.c

@@ -2650,14 +2650,19 @@ ambw_end:
       }
       s = skip_to_option_part(s);
     }
-  } else if (varp == &p_lcs) {  // 'listchars'
+  } else if (varp == &p_lcs) {  // global 'listchars'
     errmsg = set_chars_option(curwin, varp, false);
-    if (!errmsg) {
+    if (errmsg == NULL) {
+      // The current window is set to use the global 'listchars' value.
+      // So clear the window-local value.
+      if (!(opt_flags & OPT_GLOBAL)) {
+        clear_string_option(&curwin->w_p_lcs);
+      }
       FOR_ALL_TAB_WINDOWS(tp, wp) {
         set_chars_option(wp, &wp->w_p_lcs, true);
       }
+      redraw_all_later(NOT_VALID);
     }
-    redraw_all_later(NOT_VALID);
   } else if (varp == &curwin->w_p_lcs) {  // local 'listchars'
     errmsg = set_chars_option(curwin, varp, true);
   } else if (varp == &p_fcs) {  // 'fillchars'

src/nvim/testdir/test_listchars.vim

@@ -112,7 +112,7 @@ func Test_listchars()
 
   " Test lead and trail
   normal ggdG
-  set listchars=eol:$
+  set listchars=eol:$  " Accommodate Nvim default
   set listchars+=lead:>,trail:<,space:x
   set list
 
@@ -142,7 +142,7 @@ func Test_listchars()
 
   " Test multispace
   normal ggdG
-  set listchars=eol:$
+  set listchars=eol:$  " Accommodate Nvim default
   set listchars+=multispace:yYzZ
   set list
 
@@ -301,7 +301,7 @@ func Test_listchars_invalid()
   enew!
   set ff=unix
 
-  set listchars=eol:$
+  set listchars=eol:$  " Accommodate Nvim default
   set list
   set ambiwidth=double
 
@@ -365,3 +365,112 @@ func Test_listchars_composing()
   enew!
   set listchars& ff&
 endfunction
+
+" Check for the value of the 'listchars' option
+func s:CheckListCharsValue(expected)
+  call assert_equal(a:expected, &listchars)
+  call assert_equal(a:expected, getwinvar(0, '&listchars'))
+endfunc
+
+" Test for using a window local value for 'listchars'
+func Test_listchars_window_local()
+  %bw!
+  set list listchars&
+  let l:default_listchars = &listchars  " Accommodate Nvim default
+  new
+  " set a local value for 'listchars'
+  setlocal listchars=tab:+-,eol:#
+  call s:CheckListCharsValue('tab:+-,eol:#')
+  " When local value is reset, global value should be used
+  setlocal listchars=
+  call s:CheckListCharsValue(l:default_listchars)  " Accommodate Nvim default
+  " Use 'setlocal <' to copy global value
+  setlocal listchars=space:.,extends:>
+  setlocal listchars<
+  call s:CheckListCharsValue(l:default_listchars)  " Accommodate Nvim default
+  " Use 'set <' to copy global value
+  setlocal listchars=space:.,extends:>
+  set listchars<
+  call s:CheckListCharsValue(l:default_listchars)  " Accommodate Nvim default
+  " Changing global setting should not change the local setting
+  setlocal listchars=space:.,extends:>
+  setglobal listchars=tab:+-,eol:#
+  call s:CheckListCharsValue('space:.,extends:>')
+  " when split opening a new window, local value should be copied
+  split
+  call s:CheckListCharsValue('space:.,extends:>')
+  " clearing local value in one window should not change the other window
+  set listchars&
+  call s:CheckListCharsValue(l:default_listchars)  " Accommodate Nvim default
+  close
+  call s:CheckListCharsValue('space:.,extends:>')
+
+  " use different values for 'listchars' items in two different windows
+  call setline(1, ["\t  one  two  "])
+  setlocal listchars=tab:<->,lead:_,space:.,trail:@,eol:#
+  split
+  setlocal listchars=tab:[.],lead:#,space:_,trail:.,eol:&
+  split
+  set listchars=tab:+-+,lead:^,space:>,trail:<,eol:%
+  call assert_equal(['+------+^^one>>two<<%'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['[......]##one__two..&'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['<------>__one..two@@#'], ScreenLines(1, virtcol('$')))
+  " changing the global setting should not change the local value
+  setglobal listchars=tab:[.],lead:#,space:_,trail:.,eol:&
+  call assert_equal(['<------>__one..two@@#'], ScreenLines(1, virtcol('$')))
+  set listchars<
+  call assert_equal(['[......]##one__two..&'], ScreenLines(1, virtcol('$')))
+
+  " Using setglobal in a window with local setting should not affect the
+  " window. But should impact other windows using the global setting.
+  enew! | only
+  call setline(1, ["\t  one  two  "])
+  set listchars=tab:[.],lead:#,space:_,trail:.,eol:&
+  split
+  setlocal listchars=tab:+-+,lead:^,space:>,trail:<,eol:%
+  split
+  setlocal listchars=tab:<->,lead:_,space:.,trail:@,eol:#
+  setglobal listchars=tab:{.},lead:-,space:=,trail:#,eol:$
+  call assert_equal(['<------>__one..two@@#'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['+------+^^one>>two<<%'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['{......}--one==two##$'], ScreenLines(1, virtcol('$')))
+
+  " Setting the global setting to the default value should not impact a window
+  " using a local setting
+  split
+  setlocal listchars=tab:<->,lead:_,space:.,trail:@,eol:#
+  setglobal listchars=eol:$  " Accommodate Nvim default
+  call assert_equal(['<------>__one..two@@#'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['^I  one  two  $'], ScreenLines(1, virtcol('$')))
+
+  " Setting the local setting to the default value should not impact a window
+  " using a global setting
+  set listchars=tab:{.},lead:-,space:=,trail:#,eol:$
+  split
+  setlocal listchars=tab:<->,lead:_,space:.,trail:@,eol:#
+  call assert_equal(['<------>__one..two@@#'], ScreenLines(1, virtcol('$')))
+  setlocal listchars=eol:$  " Accommodate Nvim default
+  call assert_equal(['^I  one  two  $'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['{......}--one==two##$'], ScreenLines(1, virtcol('$')))
+
+  " Using set in a window with a local setting should change it to use the
+  " global setting and also impact other windows using the global setting
+  split
+  setlocal listchars=tab:<->,lead:_,space:.,trail:@,eol:#
+  call assert_equal(['<------>__one..two@@#'], ScreenLines(1, virtcol('$')))
+  set listchars=tab:+-+,lead:^,space:>,trail:<,eol:%
+  call assert_equal(['+------+^^one>>two<<%'], ScreenLines(1, virtcol('$')))
+  close
+  call assert_equal(['+------+^^one>>two<<%'], ScreenLines(1, virtcol('$')))
+
+  %bw!
+  set list& listchars&
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab

src/nvim/testdir/test_listlbr.vim

@@ -43,6 +43,7 @@ endfunc
 
 func Test_linebreak_with_list()
   throw 'skipped: Nvim does not support enc=latin1'
+  set listchars=
   call s:test_windows('setl ts=4 sbr=+ list listchars=')
   call setline(1, "\tabcdef hijklmn\tpqrstuvwxyz_1060ABCDEFGHIJKLMNOP ")
   let lines = s:screen_lines([1, 4], winwidth(0))
@@ -54,6 +55,7 @@ func Test_linebreak_with_list()
 \ ]
   call s:compare_lines(expect, lines)
   call s:close_windows()
+  set listchars&vim
 endfunc
 
 func Test_linebreak_with_nolist()

test/functional/options/chars_spec.lua

@@ -122,7 +122,7 @@ describe("'listchars'", function()
                                                         |
     ]])
   end)
-  it('has value local to window', function()
+  it('has window-local value', function()
     feed('i<tab><tab><tab><esc>')
     command('set list laststatus=0')
     command('setl listchars=tab:<->')
@@ -136,4 +136,18 @@ describe("'listchars'", function()
                                                         |
     ]])
   end)
+  it('using :set clears window-local value', function()
+    feed('i<tab><tab><tab><esc>')
+    command('set list laststatus=0')
+    command('setl listchars=tab:<->')
+    command('vsplit')
+    command('set listchars=tab:>-,eol:$')
+    screen:expect([[
+      >------->-------^>-------$│<------><------><------>|
+      ~                        │~                       |
+      ~                        │~                       |
+      ~                        │~                       |
+                                                        |
+    ]])
+  end)
 end)