feat: add draw_empty option to always draw component event when it's empty (#964)

* feat: add draw_empty option to always draw component event when it's empty

Closes #963

* tests: add test for component draw_empty option

* docs: add docs for component draw_empty option

---------

Co-authored-by: Carl Johnson <carl.darick.johnson@gmail.com>

README.md

@@ -419,6 +419,9 @@ sections = {
 
       cond = nil,           -- Condition function, the component is loaded when the function returns `true`.
 
+      draw_empty = false,   -- Whether to draw component even if it's empty.
+                            -- Might be useful if you want just the separator.
+
       -- Defines a custom color for the component:
       --
       -- 'highlight_group_name' | { fg = '#rrggbb'|cterm_value(0-255)|'color_name(red)', bg= '#rrggbb', gui='style' } | function

lua/lualine/component.lua

@@ -274,7 +274,7 @@ function M:draw(default_highlight, is_focused)
   if self.options.fmt then
     status = self.options.fmt(status or '', self)
   end
-  if type(status) == 'string' and #status > 0 then
+  if type(status) == 'string' and (#status > 0 or self.options.draw_empty) then
     self.status = status
     self:apply_icon()
     self:apply_padding()

tests/spec/component_spec.lua

@@ -211,6 +211,19 @@ describe('Component:', function()
       assert.stub(hl.component_format_highlight).was_called_with(comp2.options.color_highlight)
       hl.component_format_highlight:revert()
     end)
+
+    it('draw_empty', function()
+      local opts = build_component_opts {
+        component_separators = { left = '', right = '' },
+        padding = 0,
+        separator = '>',
+        fmt = function()
+          return ''
+        end,
+        draw_empty = true,
+      }
+      assert_component(nil, opts, '>')
+    end)
   end)
 end)