enhance: allow components to be functions too (#81)

Some components like hostname, progress are so simple that
the component class setup is just unnecessary boilerplate.
Allowing them to be function simplifies things.
With this you can put your regular component functions in
~/.config/nvim/lua/lualine/components/ folder and treat then as
regular lualine components just like 'mode' or 'branch'.
Hopefully this will help lualine plugins grow.

lua/lualine/components/encoding.lua

@@ -1,9 +1,7 @@
 -- Copyright (c) 2020-2021 hoob3rt
 -- MIT license, see LICENSE for more details.
-local M = require('lualine.component'):extend()
-
-M.update_status = function()
+local function encoding()
   return [[%{strlen(&fenc)?&fenc:&enc}]]
 end
 
-return M
+return encoding

lua/lualine/components/filesize.lua

@@ -1,8 +1,6 @@
 -- Copyright (c) 2020-2021 shadmansaleh
 -- MIT license, see LICENSE for more details.
-local M = require('lualine.component'):extend()
-
-M.update_status = function()
+local function filesize()
   local file = vim.fn.expand '%:p'
   if file == nil or #file == 0 then
     return ''
@@ -24,4 +22,4 @@ M.update_status = function()
   return string.format('%.1f%s', size, sufixes[i])
 end
 
-return M
+return filesize

lua/lualine/components/hostname.lua

@@ -1,7 +1,7 @@
 -- Copyright (c) 2020-2021 hoob3rt
 -- MIT license, see LICENSE for more details.
-local M = require('lualine.component'):extend()
+local function hostname()
+  return vim.loop.os_gethostname()
+end
 
-M.update_status = vim.loop.os_gethostname
-
-return M
+return hostname

lua/lualine/components/location.lua

@@ -1,9 +1,7 @@
 -- Copyright (c) 2020-2021 hoob3rt
 -- MIT license, see LICENSE for more details.
-local M = require('lualine.component'):extend()
-
-M.update_status = function()
+local function location()
   return [[%3l:%-2c]]
 end
 
-return M
+return location

lua/lualine/components/mode.lua

@@ -1,10 +1,4 @@
 -- Copyright (c) 2020-2021 hoob3rt
 -- MIT license, see LICENSE for more details.
-local require = require('lualine_require').require
 local get_mode = require('lualine.utils.mode').get_mode
-
-local M = require('lualine.component'):extend()
-
-M.update_status = get_mode
-
-return M
+return get_mode

lua/lualine/components/progress.lua

@@ -1,9 +1,7 @@
 -- Copyright (c) 2020-2021 hoob3rt
 -- MIT license, see LICENSE for more details.
-local M = require('lualine.component'):extend()
-
-M.update_status = function()
+local function progress()
   return [[%3P]]
 end
 
-return M
+return progress

lua/lualine/utils/loader.lua

@@ -18,7 +18,12 @@ local component_types = {
     local ok, loaded_component = pcall(require, 'lualine.components.' .. component[1])
     if ok then
       component.component_name = component[1]
+      if type(loaded_component) == 'table' then
         loaded_component = loaded_component(component)
+      elseif type(loaded_component) == 'function' then
+        component[1] = loaded_component
+        loaded_component = require 'lualine.components.special.function_component'(component)
+      end
       return loaded_component
     end
   end,

lua/tests/helpers.lua

@@ -16,8 +16,16 @@ M.assert_component = function(component, opts, result)
   -- for testing global options
   if component == nil then
     component = 'special.function_component'
+  else
+    opts.component_name = component
+  end
+  local comp = require('lualine.components.' .. component)
+  if type(comp) == 'table' then
+    comp = comp(opts)
+  elseif type(comp) == 'function' then
+    opts[1] = comp
+    comp = require 'lualine.components.special.function_component'(opts)
   end
-  local comp = require('lualine.components.' .. component)(opts)
   eq(result, comp:draw(opts.hl))
 end