fix(statusline): default 'statusline' improvements #41597

Problem: there should be exactly one cell of padding between sections,
and exactly one cell of minimum padding between the left and the right.
- Spaces between sections waste space when a section is empty.
  According to a comment in #33036, this was the reason to avoid `%k`
  and implement the keymap section with a vim expression, but other
  sections still have this problem.
- The diagnostics section wastes space because it is not entirely empty
  when there are diagnostics in another buffer.
- The terminal exit code section can touch the right side, e.g. the
  ruler, even though it belongs to the left side.
Solution:
- Use auto-hiding item groups (`%(` without width fields) to get rid of
  unneeded spaces when a section shows no information.
  This simplifies the 'showcmd' and 'keymap' sections in particular.
- As a slight simplification, `term_exitcode` is moved into the flags
  section since it is formatted with square brackets like a flag.
- Count the diagnostics for the current buffer specifically.
- Ensure at least one cell of padding between the left and the right
  side by adding a space next to the separator `%=`.

Problem: some sections are implemented with `%{%`, even though
reevaluation of the expression result is not needed.
This leads to otherwise needless %-escaping in `progress_status`.
Solution: use `%{` instead.

Problem: `%{` and `%{%` (without items) replace spaces with fillchars.
This looks out-of-place inside the terminal exit code section, and in
contrast to all other sections, the 'busy' section is surrounded by
fillchars, which looks inconsistent, and with some terminal-font
combinations, ◐ overlaps the fillchar, e.g. Alacritty & JetBrains Mono.
Solution: use non-breaking spaces U+202F to avoid fillchar substitution.

Problem: sections that appear/disappear frequently can make otherwise
more stable sections jump around a lot.
Solution: sort the sections on the right roughly by volatility:
'showcmd' in first place, 'keymap' next to the ruler.

runtime/lua/vim/_core/util.lua

@@ -121,7 +121,8 @@ function M.term_exitcode()
 
   local info = vim.api.nvim_get_chan_info(chan_id)
   if info.exitcode and info.exitcode >= 0 then
-    return string.format('[Exit: %d]', info.exitcode)
+    -- use non-breaking space to avoid fillchar
+    return string.format('[Exit:\226\128\175%d]', info.exitcode)
   end
   return ''
 end

runtime/lua/vim/_meta/options.gen.lua

@@ -7074,7 +7074,7 @@ vim.wo.stc = vim.wo.statuscolumn
 ---
 ---
 --- @type string
-vim.o.statusline = "%<%f %h%w%m%r %{% v:lua.require('vim._core.util').term_exitcode() %}%=%{% luaeval('(package.loaded[''vim.ui''] and vim.api.nvim_get_current_win() == tonumber(vim.g.actual_curwin or -1) and vim.ui.progress_status()) or '''' ')%}%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}%{% &busy > 0 ? '◐ ' : '' %}%{% luaeval('(package.loaded[''vim.diagnostic''] and next(vim.diagnostic.count()) and vim.diagnostic.status() .. '' '') or '''' ') %}%{% &ruler ? &rulerformat : '' %}"
+vim.o.statusline = "%<%f%( %h%w%m%r%{ v:lua.require('vim._core.util').term_exitcode() }%)%= %(%-10S %)%{ &busy > 0 ? '◐ ' : '' }%(%{ luaeval('(package.loaded[''vim.ui''] and vim.api.nvim_get_current_win() == tonumber(vim.g.actual_curwin or -1) and vim.ui.progress_status()) or '''' ')} %)%{% luaeval('(package.loaded[''vim.diagnostic''] and next(vim.diagnostic.count(0)) and vim.diagnostic.status() .. '' '') or '''' ') %}%(%k %)%{% &ruler ? &rulerformat : '' %}"
 vim.o.stl = vim.o.statusline
 vim.wo.statusline = vim.o.statusline
 vim.wo.stl = vim.wo.statusline

runtime/lua/vim/ui.lua

@@ -385,7 +385,7 @@ do
         sum = sum + (progress_item.percent or 0)
       end
       local avg = math.floor(sum / count)
-      return string.format('%d%%%%(%d) ', avg, count)
+      return string.format('%d%%(%d)', avg, count)
     end
   end
 

src/nvim/options.lua

@@ -9114,14 +9114,14 @@ local options = {
       defaults = {
         if_true = table.concat({
           '%<', -- guards the default truncation from the left against a %< injected via rulerformat
-          '%f %h%w%m%r ',
-          "%{% v:lua.require('vim._core.util').term_exitcode() %}",
-          '%=',
-          "%{% luaeval('(package.loaded[''vim.ui''] and vim.api.nvim_get_current_win() == tonumber(vim.g.actual_curwin or -1) and vim.ui.progress_status()) or '''' ')%}",
-          "%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}",
-          "%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}",
-          "%{% &busy > 0 ? '◐ ' : '' %}",
-          "%{% luaeval('(package.loaded[''vim.diagnostic''] and next(vim.diagnostic.count()) and vim.diagnostic.status() .. '' '') or '''' ') %}",
+          '%f',
+          "%( %h%w%m%r%{ v:lua.require('vim._core.util').term_exitcode() }%)",
+          '%= ',
+          '%(%-10S %)',
+          "%{ &busy > 0 ? '◐\226\128\175' : '' }", -- use non-breaking space to avoid fillchar
+          "%(%{ luaeval('(package.loaded[''vim.ui''] and vim.api.nvim_get_current_win() == tonumber(vim.g.actual_curwin or -1) and vim.ui.progress_status()) or '''' ')} %)",
+          "%{% luaeval('(package.loaded[''vim.diagnostic''] and next(vim.diagnostic.count(0)) and vim.diagnostic.status() .. '' '') or '''' ') %}",
+          '%(%k %)',
           "%{% &ruler ? &rulerformat : '' %}",
         }),
         doc = 'is very long',

test/functional/ui/statusline_spec.lua

@@ -1152,14 +1152,14 @@ describe('default statusline', function()
 
     local default_statusline = table.concat({
       '%<',
-      '%f %h%w%m%r ',
-      "%{% v:lua.require('vim._core.util').term_exitcode() %}",
-      '%=',
-      "%{% luaeval('(package.loaded[''vim.ui''] and vim.api.nvim_get_current_win() == tonumber(vim.g.actual_curwin or -1) and vim.ui.progress_status()) or '''' ')%}",
-      "%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}",
-      "%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}",
-      "%{% &busy > 0 ? '◐ ' : '' %}",
-      "%{% luaeval('(package.loaded[''vim.diagnostic''] and next(vim.diagnostic.count()) and vim.diagnostic.status() .. '' '') or '''' ') %}",
+      '%f',
+      "%( %h%w%m%r%{ v:lua.require('vim._core.util').term_exitcode() }%)",
+      '%= ',
+      '%(%-10S %)',
+      "%{ &busy > 0 ? '◐\226\128\175' : '' }",
+      "%(%{ luaeval('(package.loaded[''vim.ui''] and vim.api.nvim_get_current_win() == tonumber(vim.g.actual_curwin or -1) and vim.ui.progress_status()) or '''' ')} %)",
+      "%{% luaeval('(package.loaded[''vim.diagnostic''] and next(vim.diagnostic.count(0)) and vim.diagnostic.status() .. '' '') or '''' ') %}",
+      '%(%k %)',
       "%{% &ruler ? &rulerformat : '' %}",
     })
 
@@ -1210,7 +1210,7 @@ describe('default statusline', function()
     screen:expect([[
       ^                                                            |
       {1:~                                                           }|*13
-      {3:[No Name]                               ◐ 0,0-1          All}|
+      {3:[No Name]                               ◐ 0,0-1          All}|
                                                                   |
     ]])
 
@@ -1229,7 +1229,7 @@ describe('default statusline', function()
     api.nvim_set_option_value('shellcmdflag', 'EXIT', {})
     api.nvim_set_option_value('shellxquote', '', {}) -- win: avoid extra quotes
     command('terminal 9')
-    screen:expect({ any = '%[Exit: 9%]' })
+    screen:expect({ any = '%[Exit:\226\128\1759%]' })
     expect_exitcode(9)
   end)
 
@@ -1237,8 +1237,7 @@ describe('default statusline', function()
     exec_lua("vim.o.statusline = ''")
     local function get_progress()
       return exec_lua(function()
-        local stl_str = vim.ui.progress_status()
-        return vim.api.nvim_eval_statusline(stl_str, {}).str
+        return vim.ui.progress_status()
       end)
     end
 
@@ -1249,7 +1248,7 @@ describe('default statusline', function()
       true,
       { kind = 'progress', source = 'tests', title = 'test', status = 'running', percent = 10 }
     )
-    eq('10%(1) ', get_progress())
+    eq('10%(1)', get_progress())
 
     api.nvim_echo({ { 'searching' } }, true, {
       id = id1,
@@ -1259,7 +1258,7 @@ describe('default statusline', function()
       status = 'running',
       title = 'terminal(ripgrep)',
     })
-    eq('50%(1) ', get_progress())
+    eq('50%(1)', get_progress())
 
     api.nvim_echo({ { 'searching...' } }, true, {
       kind = 'progress',
@@ -1268,7 +1267,7 @@ describe('default statusline', function()
       status = 'running',
       percent = 20,
     })
-    eq('35%(2) ', get_progress())
+    eq('35%(2)', get_progress())
 
     api.nvim_echo({ { 'searching' } }, true, {
       id = id1,
@@ -1278,7 +1277,7 @@ describe('default statusline', function()
       status = 'success',
       title = 'terminal(ripgrep)',
     })
-    eq('20%(1) ', get_progress())
+    eq('20%(1)', get_progress())
 
     exec('redrawstatus')
     screen:expect([[