feat(statusline): vim.diagnostic.status() #33723

Problem:
Not easy to get a status string for diagnostics.

Solution:
- Add vim.diagnostic.status().
- Add it to the default 'statusline'.

runtime/doc/diagnostic.txt

@@ -1019,6 +1019,23 @@ show({namespace}, {bufnr}, {diagnostics}, {opts})
       • {opts}         (`vim.diagnostic.Opts?`) Display options. See
                        |vim.diagnostic.Opts|.
 
+status({bufnr})                                      *vim.diagnostic.status()*
+    Returns formatted string with diagnostics for the current buffer. The
+    severities with 0 diagnostics are left out. Example `E:2 W:3 I:4 H:5`
+
+    To customise appearance, set diagnostic signs text with >lua
+        vim.diagnostic.config({
+          signs = { text = { [vim.diagnostic.severity.ERROR] = 'e', ... } }
+        })
+<
+
+    Parameters: ~
+      • {bufnr}  (`integer?`) Buffer number to get diagnostics from. Defaults
+                 to 0 for the current buffer
+
+    Return: ~
+        (`string`)
+
 toqflist({diagnostics})                            *vim.diagnostic.toqflist()*
     Convert a list of diagnostics to a list of quickfix items that can be
     passed to |setqflist()| or |setloclist()|.

runtime/doc/news.txt

@@ -145,6 +145,7 @@ DEFAULTS
 
 • 'statusline' default is exposed as a statusline expression (previously it
   was implemented as an internal C routine).
+• 'statusline' includes |vim.diagnostic.status()|
 • Project-local configuration ('exrc') is also loaded from parent directories.
   Unset 'exrc' to stop further search.
 • Mappings:
@@ -157,6 +158,8 @@ DIAGNOSTICS
   location/quickfix list.
 • |vim.diagnostic.get()| now accepts an `enabled` filter to only return
   enabled or disabled diagnostics.
+• |vim.diagnostic.status()| returns a formatted string with current buffer
+  diagnostics
 
 EDITOR
 

runtime/doc/options.txt

@@ -6231,7 +6231,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	an expensive expression can negatively affect render performance.
 
 					*'statusline'* *'stl'* *E540* *E542*
-'statusline' 'stl'	string	(default "%<%f %h%w%m%r %=%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}%{% &busy > 0 ? '◐ ' : '' %}%{% &ruler ? ( &rulerformat == '' ? '%-14.(%l,%c%V%) %P' : &rulerformat ) : '' %}")
+'statusline' 'stl'	string	(default is very long)
 			global or local to window |global-local|
 	Sets the |status-line|.
 

runtime/lua/vim/_meta/options.lua

@@ -6909,7 +6909,7 @@ vim.wo.stc = vim.wo.statuscolumn
 ---
 ---
 --- @type string
-vim.o.statusline = "%<%f %h%w%m%r %=%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}%{% &busy > 0 ? '◐ ' : '' %}%{% &ruler ? ( &rulerformat == '' ? '%-14.(%l,%c%V%) %P' : &rulerformat ) : '' %}"
+vim.o.statusline = "%<%f %h%w%m%r %=%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}%{% &busy > 0 ? '◐ ' : '' %}%(%{luaeval('(pcall(require, ''vim.diagnostic'') and vim.diagnostic.status()) or '''' ')} %)%{% &ruler ? ( &rulerformat == '' ? '%-14.(%l,%c%V%) %P' : &rulerformat ) : '' %}"
 vim.o.stl = vim.o.statusline
 vim.wo.statusline = vim.o.statusline
 vim.wo.stl = vim.wo.statusline

runtime/lua/vim/diagnostic.lua

@@ -2840,4 +2840,42 @@ function M.fromqflist(list)
   return diagnostics
 end
 
+--- Returns formatted string with diagnostics for the current buffer.
+--- The severities with 0 diagnostics are left out.
+--- Example `E:2 W:3 I:4 H:5`
+---
+--- To customise appearance, set diagnostic signs text with
+--- ```lua
+--- vim.diagnostic.config({
+---   signs = { text = { [vim.diagnostic.severity.ERROR] = 'e', ... } }
+--- })
+--- ```
+---@param bufnr? integer Buffer number to get diagnostics from.
+---                      Defaults to 0 for the current buffer
+---
+---@return string
+function M.status(bufnr)
+  vim.validate('bufnr', bufnr, 'number', true)
+  bufnr = bufnr or 0
+  local counts = M.count(bufnr)
+  local user_signs = vim.tbl_get(M.config() --[[@as vim.diagnostic.Opts]], 'signs', 'text') or {}
+  local signs = vim.tbl_extend('keep', user_signs, { 'E', 'W', 'I', 'H' })
+  local result_str = vim
+    .iter(pairs(counts))
+    :map(function(severity, count)
+      return ('%s:%s'):format(signs[severity], count)
+    end)
+    :join(' ')
+
+  return result_str
+end
+
+vim.api.nvim_create_autocmd('DiagnosticChanged', {
+  group = vim.api.nvim_create_augroup('nvim.diagnostic.status', {}),
+  callback = function(ev)
+    vim.api.nvim__redraw({ buf = ev.buf, statusline = true })
+  end,
+  desc = 'diagnostics component for the statusline',
+})
+
 return M

src/nvim/options.lua

@@ -8706,15 +8706,19 @@ local options = {
     {
       abbreviation = 'stl',
       cb = 'did_set_statusline',
-      defaults = table.concat({
-        '%<',
-        '%f %h%w%m%r ',
-        '%=',
-        "%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}",
-        "%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}",
-        "%{% &busy > 0 ? '◐ ' : '' %}",
-        "%{% &ruler ? ( &rulerformat == '' ? '%-14.(%l,%c%V%) %P' : &rulerformat ) : '' %}",
-      }),
+      defaults = {
+        if_true = table.concat({
+          '%<',
+          '%f %h%w%m%r ',
+          '%=',
+          "%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}",
+          "%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}",
+          "%{% &busy > 0 ? '◐ ' : '' %}",
+          "%(%{luaeval('(pcall(require, ''vim.diagnostic'') and vim.diagnostic.status()) or '''' ')} %)",
+          "%{% &ruler ? ( &rulerformat == '' ? '%-14.(%l,%c%V%) %P' : &rulerformat ) : '' %}",
+        }),
+        doc = 'is very long',
+      },
       desc = [=[
         Sets the |status-line|.
 

test/functional/lua/diagnostic_spec.lua

@@ -4022,6 +4022,72 @@ describe('vim.diagnostic', function()
     end)
   end)
 
+  describe('status()', function()
+    it('returns empty string if no diagnostics', function()
+      local result = exec_lua(function()
+        vim.diagnostic.set(_G.diagnostic_ns, _G.diagnostic_bufnr, {})
+        return vim.diagnostic.status()
+      end)
+
+      eq('', result)
+    end)
+
+    it('returns count for each diagnostic kind', function()
+      local result = exec_lua(function()
+        vim.diagnostic.set(_G.diagnostic_ns, 0, {
+          _G.make_error('Error 1', 0, 1, 0, 1),
+
+          _G.make_warning('Warning 1', 2, 2, 2, 2),
+          _G.make_warning('Warning 2', 2, 2, 2, 2),
+
+          _G.make_info('Info 1', 3, 3, 3, 3),
+          _G.make_info('Info 2', 3, 3, 3, 3),
+          _G.make_info('Info 3', 3, 3, 3, 3),
+
+          _G.make_hint('Hint 1', 4, 4, 4, 4),
+          _G.make_hint('Hint 2', 4, 4, 4, 4),
+          _G.make_hint('Hint 3', 4, 4, 4, 4),
+          _G.make_hint('Hint 4', 4, 4, 4, 4),
+        })
+        return vim.diagnostic.status()
+      end)
+
+      eq('E:1 W:2 I:3 H:4', result)
+
+      exec_lua('vim.cmd.enew()')
+
+      -- Empty diagnostics for a buffer without diagnostics
+      eq(
+        '',
+        exec_lua(function()
+          return vim.diagnostic.status()
+        end)
+      )
+    end)
+
+    it('uses text from diagnostic.config().signs.text[severity]', function()
+      local result = exec_lua(function()
+        vim.diagnostic.config({
+          signs = {
+            text = {
+              [vim.diagnostic.severity.ERROR] = '⨯',
+              [vim.diagnostic.severity.WARN] = '⚠︎',
+            },
+          },
+        })
+
+        vim.diagnostic.set(_G.diagnostic_ns, 0, {
+          _G.make_error('Error 1', 0, 1, 0, 1),
+          _G.make_warning('Warning 1', 2, 2, 2, 2),
+        })
+
+        return vim.diagnostic.status()
+      end)
+
+      eq('⨯:1 ⚠︎:1', result)
+    end)
+  end)
+
   describe('handlers', function()
     it('checks that a new handler is a table', function()
       matches(

test/functional/ui/statusline_spec.lua

@@ -792,6 +792,7 @@ describe('default statusline', function()
       "%{% &showcmdloc == 'statusline' ? '%-10.S ' : '' %}",
       "%{% exists('b:keymap_name') ? '<'..b:keymap_name..'> ' : '' %}",
       "%{% &busy > 0 ? '◐ ' : '' %}",
+      "%(%{luaeval('(pcall(require, ''vim.diagnostic'') and vim.diagnostic.status()) or '''' ')} %)",
       "%{% &ruler ? ( &rulerformat == '' ? '%-14.(%l,%c%V%) %P' : &rulerformat ) : '' %}",
     })
 

test/old/testdir/test_options.vim

@@ -2690,7 +2690,7 @@ func GetGlobalLocalWindowOptions()
   " Filter for global or local to window
   v/^'.*'.*\n.*global or local to window |global-local/d
   " get option value and type
-  sil %s/^'\([^']*\)'.*'\s\+\(\w\+\)\s\+(default \%(\(".*"\|\d\+\|empty\)\).*/\1 \2 \3/g
+  sil %s/^'\([^']*\)'.*'\s\+\(\w\+\)\s\+(default \%(\(".*"\|\d\+\|empty\|is very long\)\).*/\1 \2 \3/g
   " sil %s/empty/""/g
   " split the result
   " let result=getline(1,'$')->map({_, val -> split(val, ' ')})
@@ -2705,6 +2705,10 @@ func Test_set_option_window_global_local_all()
   let optionlist = GetGlobalLocalWindowOptions()
   for [opt, type, default] in optionlist
     let _old = eval('&g:' .. opt)
+    if opt == 'statusline'
+      " parsed default value is "is very long" as it is a doc string, not actual value
+      let default = "\"" . _old . "\""
+    endif
     if type == 'string'
       if opt == 'fillchars'
         exe 'setl ' .. opt .. '=vert:+'