enhance: check for new diagnostics highlight groups

- Now DiagnosticError, DiagnosticWarn, DiagnosticInfo, DiagnosticHint
  are also consider3d for default highlight in diagnostics component.
- Moved getHl from auto theme to utils as extract_color_from_hllist

closes #56

lua/lualine/components/diagnostics.lua

@@ -53,24 +53,32 @@ local default_options = {
   sections = { 'error', 'warn', 'info', 'hint' },
   diagnostics_color = {
     error = {
-      fg = modules.utils.extract_highlight_colors('LspDiagnosticsDefaultError', 'fg')
-        or modules.utils.extract_highlight_colors('DiffDelete', 'fg')
-        or '#e32636',
+      fg = modules.utils.extract_color_from_hllist(
+        'fg',
+        { 'DiagnosticError', 'LspDiagnosticsDefaultError', 'DiffDelete' },
+        '#e32636'
+      ),
     },
     warn = {
-      fg = modules.utils.extract_highlight_colors('LspDiagnosticsDefaultWarning', 'fg')
-        or modules.utils.extract_highlight_colors('DiffText', 'fg')
-        or '#ffa500',
+      fg = modules.utils.extract_color_from_hllist(
+        'fg',
+        { 'DiagnosticWarn', 'LspDiagnosticsDefaultWarning', 'DiffText' },
+        '#ffa500'
+      ),
     },
     info = {
-      fg = modules.utils.extract_highlight_colors('LspDiagnosticsDefaultInformation', 'fg')
-        or modules.utils.extract_highlight_colors('Normal', 'fg')
-        or '#ffffff',
+      fg = modules.utils.extract_color_from_hllist(
+        'fg',
+        { 'DiagnosticInfo', 'LspDiagnosticsDefaultInformation', 'Normal' },
+        '#ffffff'
+      ),
     },
     hint = {
-      fg = modules.utils.extract_highlight_colors('LspDiagnosticsDefaultHint', 'fg')
-        or modules.utils.extract_highlight_colors('DiffChange', 'fg')
-        or '#273faf',
+      fg = modules.utils.extract_color_from_hllist(
+        'fg',
+        { 'DiagnosticHint', 'LspDiagnosticsDefaultHint', 'DiffChange' },
+        '#273faf'
+      ),
     },
   },
 }

lua/lualine/themes/auto.lua

@@ -19,27 +19,6 @@ local contrast_threshold = 0.3
 -- how much brightness is changed in percentage for light and dark themes
 local brightness_modifier_parameter = 10
 
--- retrives color value from highlight group name in syntax_list
--- first present highlight is returned
-local function getHi(scope, syntaxlist)
-  for _, highlight_name in pairs(syntaxlist) do
-    if vim.fn.hlexists(highlight_name) ~= 0 then
-      local color = utils.extract_highlight_colors(highlight_name)
-      if color.reverse then
-        if scope == 'bg' then
-          scope = 'fg'
-        else
-          scope = 'bg'
-        end
-      end
-      if color[scope] then
-        return color[scope]
-      end
-    end
-  end
-  return '#000000'
-end
-
 -- truns #rrggbb -> { red, green, blue }
 local function rgb_str2num(rgb_color_str)
   if rgb_color_str:find '#' == 1 then
@@ -124,14 +103,14 @@ end
 -- Get the colors to create theme
 -- stylua: ignore
 local colors = {
-  normal  = getHi('bg', { 'PmenuSel', 'PmenuThumb', 'TabLineSel' }),
-  insert  = getHi('fg', { 'String', 'MoreMsg' }),
-  replace = getHi('fg', { 'Number', 'Type' }),
-  visual  = getHi('fg', { 'Special', 'Boolean', 'Constant' }),
-  command = getHi('fg', { 'Identifier' }),
-  back1   = getHi('bg', { 'Normal', 'StatusLineNC' }),
-  fore    = getHi('fg', { 'Normal', 'StatusLine' }),
-  back2   = getHi('bg', { 'StatusLine' }),
+  normal  = utils.extract_color_from_hllist('bg', { 'PmenuSel', 'PmenuThumb', 'TabLineSel' }, '#000000'),
+  insert  = utils.extract_color_from_hllist('fg', { 'String', 'MoreMsg' }, '#000000'),
+  replace = utils.extract_color_from_hllist('fg', { 'Number', 'Type' }, '#000000'),
+  visual  = utils.extract_color_from_hllist('fg', { 'Special', 'Boolean', 'Constant' }, '#000000'),
+  command = utils.extract_color_from_hllist('fg', { 'Identifier' }, '#000000'),
+  back1   = utils.extract_color_from_hllist('bg', { 'Normal', 'StatusLineNC' }, '#000000'),
+  fore    = utils.extract_color_from_hllist('fg', { 'Normal', 'StatusLine' }, '#000000'),
+  back2   = utils.extract_color_from_hllist('bg', { 'StatusLine' }, '#000000'),
 }
 
 -- Change brightness of colors

lua/lualine/utils/utils.lua

@@ -23,6 +23,27 @@ function M.extract_highlight_colors(color_group, scope)
   return color
 end
 
+-- retrives color value from highlight group name in syntax_list
+-- first present highlight is returned
+function M.extract_color_from_hllist(scope, syntaxlist, default)
+  for _, highlight_name in ipairs(syntaxlist) do
+    if vim.fn.hlexists(highlight_name) ~= 0 then
+      local color = M.extract_highlight_colors(highlight_name)
+      if color.reverse then
+        if scope == 'bg' then
+          scope = 'fg'
+        else
+          scope = 'bg'
+        end
+      end
+      if color[scope] then
+        return color[scope]
+      end
+    end
+  end
+  return default
+end
+
 -- remove empty strings from list
 function M.list_shrink(list)
   local new_list = {}