[Breaking] Refactor: switch to %{%expr%} from %!expr

Huge change to internal mechanics.
- Now %{%expr%} blocks are used for evaluating statusline instead of
  %!expr . Pros for this is statusline is evaluated on current win and
  buf context instead of active win & bufs context.
- Now all components branch & diff(These two are cached) including users
  function components updates on inactive status.
  - now components update status and function components receive an
    argument (is_focused) when called. It indicates whether it's running
    for active or inactive statusline.
- Now lualine no longer aggrasively takes over 'statusline' option.
  instead it sets the global version of statusline option. So it's
  possible to unset it to hide lualine . Or set buffer local version
  of that option to have different statusline then lualine on thay
  buffer
- Switch vim.o to vim.go or vim.opt.
- BugFix autcommands being set everytime an instence of diff or branch
  component is created
- Added new utils functions define_autocmd & is_focused
- Remove utils function lualine_eval
- Removed hacky require cache modification from component.lua

lua/lualine/component.lua

@@ -5,14 +5,6 @@ local highlight = require 'lualine.highlight'
 -- Used to provide a unique id for each component
 local component_no = 1
 
--- Here we're manupulation the require() cache so when we
--- require('lualine.component.components') it will return this table
--- It's hacky but package.loaded is documented in lua docs so from
--- standereds point of view we're good ]. I think it's better than
--- modifiying global state
-package.loaded['lualine.component.components'] = {}
-local components = package.loaded['lualine.component.components']
-
 local Component = {
   -- Creates a new component
   new = function(self, options, child)
@@ -27,7 +19,6 @@ local Component = {
         new_component.options.component_name = tostring(component_no)
       end
       new_component.component_no = component_no
-      components[component_no] = new_component
       new_component:set_separator()
       new_component:create_option_highlights()
     end
@@ -157,22 +148,13 @@ local Component = {
   -- luacheck: pop
 
   -- Driver code of the class
-  draw = function(self, default_highlight, statusline_inactive)
-    -- Check if we are in in inactive state and need to enable inactive_eval
-    -- for this compoennt
-    if self.inactive_eval and not statusline_inactive and vim.g.statusline_winid ~=
-        vim.fn.win_getid() then
-      -- In that case we'll return a evaluator
-      self.status = '%' .. string.format(
-                        '{%%v:lua.require\'lualine.utils.utils\'.lualine_eval(%s,\'\',v:true)%%}',
-                        tostring(self.component_no))
-      return self.status
-    end
+  draw = function(self, default_highlight, is_focused)
     self.status = ''
+
     if self.options.condition ~= nil and self.options.condition() ~= true then
       return self.status
     end
-    local status = self:update_status()
+    local status = self:update_status(is_focused)
     if self.options.format then status = self.options.format(status or '') end
     if type(status) == 'string' and #status > 0 then
       self.status = status
@@ -181,10 +163,8 @@ local Component = {
       self:apply_padding()
       self:apply_section_separators()
       self:apply_highlights(default_highlight)
-      if not (statusline_inactive and self.last_component) then
       self:apply_separator()
     end
-    end
     return self.status
   end
 }

lua/lualine/components/branch.lua

@@ -1,14 +1,14 @@
 -- Copyright (c) 2020-2021 shadmansaleh
 -- MIT license, see LICENSE for more details.
+local utils = require('lualine.utils.utils')
 local Branch = require('lualine.component'):new()
-
 -- vars
 Branch.git_branch = ''
 -- os specific path separator
 Branch.sep = package.config:sub(1, 1)
 -- event watcher to watch head file
 Branch.file_changed = vim.loop.new_fs_event()
-
+local branch_cache = {} -- stores last known branch for a buffer
 -- Initilizer
 Branch.new = function(self, options, child)
   local new_branch = self._parent:new(options, child or Branch)
@@ -18,11 +18,14 @@ Branch.new = function(self, options, child)
   -- run watch head on load so branch is present when component is loaded
   Branch.update_branch()
   -- update branch state of BufEnter as different Buffer may be on different repos
-  vim.cmd [[autocmd lualine BufEnter * lua require'lualine.components.branch'.update_branch()]]
+  utils.define_autocmd('BufEnter', "lua require'lualine.components.branch'.update_branch()")
   return new_branch
 end
 
-Branch.update_status = function() return Branch.git_branch end
+Branch.update_status = function(_, is_focused)
+  if not is_focused then return branch_cache[vim.fn.bufnr()] or '' end
+  return Branch.git_branch
+end
 
 -- returns full path to git directory for current directory
 function Branch.find_git_dir()
@@ -90,6 +93,7 @@ function Branch.update_branch()
     -- set to '' when git dir was not found
     Branch.git_branch = ''
   end
+  branch_cache[vim.fn.bufnr()] = Branch.git_branch
 end
 
 return Branch

lua/lualine/components/diff.lua

@@ -20,6 +20,8 @@ Diff.default_colors = {
   modified = '#ff0038'
 }
 
+local diff_cache = {} -- Stores last known value of diff of a buffer
+
 -- Initializer
 Diff.new = function(self, options, child)
   local new_instance = self._parent:new(options, child or Diff)
@@ -64,22 +66,22 @@ Diff.new = function(self, options, child)
 
   if type(new_instance.options.source) ~= 'function' then
     -- setup internal source
-    vim.cmd [[
-      autocmd lualine BufEnter     * lua require'lualine.components.diff'.update_diff_args()
-      autocmd lualine BufWritePost * lua require'lualine.components.diff'.update_git_diff()
-    ]]
+    utils.define_autocmd('BufEnter', "lua require'lualine.components.diff'.update_diff_args()")
+    utils.define_autocmd('BufWritePost', "lua require'lualine.components.diff'.update_git_diff()")
   end
 
   return new_instance
 end
 
 -- Function that runs everytime statusline is updated
-Diff.update_status = function(self)
+Diff.update_status = function(self, is_focused)
+  local git_diff = Diff.git_diff
   if self.options.source then
-    Diff.git_diff = self.options.source()
+    git_diff = self.options.source()
   end
 
-  if Diff.git_diff == nil then return '' end
+  if not is_focused then git_diff = diff_cache[vim.fn.bufnr()] or {} end
+  if git_diff == nil then return '' end
 
   local colors = {}
   if self.options.colored then
@@ -92,12 +94,12 @@ Diff.update_status = function(self)
   local result = {}
   -- loop though data and load available sections in result table
   for _, name in ipairs {'added', 'modified', 'removed'} do
-    if Diff.git_diff[name] and Diff.git_diff[name] > 0 then
+    if git_diff[name] and git_diff[name] > 0 then
       if self.options.colored then
         table.insert(result, colors[name] .. self.options.symbols[name] ..
-                         Diff.git_diff[name])
+                         git_diff[name])
       else
-        table.insert(result, self.options.symbols[name] .. Diff.git_diff[name])
+        table.insert(result, self.options.symbols[name] .. git_diff[name])
       end
     end
   end
@@ -180,6 +182,7 @@ function Diff.update_diff_args()
       else
         Diff.git_diff = {added = 0, modified = 0, removed = 0}
       end
+      diff_cache[vim.fn.bufnr()] = Diff.git_diff
     end
   }
   Diff.update_git_diff()

lua/lualine/components/filename.lua

@@ -2,8 +2,6 @@
 -- MIT license, see LICENSE for more details.
 local FileName = require('lualine.component'):new()
 
-FileName.inactive_eval = true
-
 local function count(base, pattern)
   return select(2, string.gsub(base, pattern, ''))
 end

lua/lualine/components/filetype.lua

@@ -30,7 +30,7 @@ function FileType:apply_icon()
     if icon and self.options.colored then
       local highlight_color = utils.extract_highlight_colors(
                                   icon_highlight_group, 'fg')
-      local is_focused = vim.g.statusline_winid == vim.fn.win_getid()
+      local is_focused = utils.is_focused()
       local default_highlight = highlight.format_highlight(is_focused,
                                                            self.options.self
                                                                .section)

lua/lualine/components/special/function_component.lua

@@ -1,8 +1,8 @@
 local FunctionComponent = require('lualine.component'):new()
 
-FunctionComponent.update_status = function(self)
+FunctionComponent.update_status = function(self, is_focused)
   -- 1st element in options table is the function provided by config
-  return self.options[1]()
+  return self.options[1](is_focused)
 end
 
 return FunctionComponent

lua/lualine/highlight.lua

@@ -51,7 +51,7 @@ end
 function M.create_highlight_groups(theme)
   utils.clear_highlights()
   active_theme = theme
-  if not vim.o.termguicolors then
+  if not vim.opt.termguicolors:get() then
     cterm_colors = require 'lualine.utils.cterm_colors'
   end
   for mode, sections in pairs(theme) do
@@ -154,7 +154,7 @@ function M.component_format_highlight(highlight_name)
   if highlight_name:find('no_mode') == #highlight_name - #'no_mode' + 1 then
     return '%#' .. highlight_group .. '#'
   end
-  if vim.g.statusline_winid == vim.fn.win_getid() then
+  if utils.is_focused() then
     highlight_group = append_mode(highlight_group)
   else
     highlight_group = highlight_group .. '_inactive'

lua/lualine/init.lua

@@ -3,6 +3,7 @@
 local highlight = require('lualine.highlight')
 local loader = require('lualine.utils.loader')
 local utils_section = require('lualine.utils.section')
+local utils = require('lualine.utils.utils')
 local config_module = require('lualine.config')
 
 local config = config_module.config
@@ -145,9 +146,8 @@ end
 
 local function status_dispatch()
   -- disable on specific filetypes
-  local current_ft = vim.api.nvim_buf_get_option(
-                         vim.fn.winbufnr(vim.g.statusline_winid), 'filetype')
-  local is_focused = vim.g.statusline_winid == vim.fn.win_getid()
+  local current_ft = vim.bo.filetype
+  local is_focused = utils.is_focused()
   for _, ft in pairs(config.options.disabled_filetypes) do
     if ft == current_ft then
       vim.wo.statusline = ''
@@ -195,19 +195,17 @@ end
 
 local function set_tabline()
   if next(config.tabline) ~= nil then
-    vim.o.tabline = '%!v:lua.require\'lualine\'.tabline()'
-    vim.o.showtabline = 2
+    vim.go.tabline = "%{%v:lua.require'lualine'.tabline()%}"
+    vim.go.showtabline = 2
   end
 end
 
 local function set_statusline()
   if next(config.sections) ~= nil or next(config.inactive_sections) ~= nil then
-    vim.o.statusline = '%!v:lua.require\'lualine\'.statusline()'
-    vim.api.nvim_exec([[
-      autocmd lualine WinLeave,BufLeave * lua vim.wo.statusline=require'lualine'.statusline()
-      autocmd lualine BufWinEnter,WinEnter,BufEnter,SessionLoadPost * set statusline<
+    vim.go.statusline = "%{%v:lua.require'lualine'.statusline()%}"
+    vim.cmd([[
       autocmd lualine VimResized * redrawstatus
-    ]], false)
+    ]])
   end
 end
 

lua/lualine/themes/papercolor.lua

@@ -1,6 +1,6 @@
 -- Copyright (c) 2020-2021 shadmansaleh
 -- MIT license, see LICENSE for more details.
 -- Credit: itchyny(lightline)
-local background = vim.o.background
+local background = vim.opt.background:get()
 
 return require('lualine.themes.papercolor_' .. background)

lua/lualine/themes/solarized.lua

@@ -2,6 +2,6 @@
 -- MIT license, see LICENSE for more details.
 -- Credit: itchyny(lightline)
 -- License: MIT License
-local background = vim.o.background
+local background = vim.opt.background:get()
 
 return require('lualine.themes.solarized_' .. background)

lua/lualine/utils/section.lua

@@ -15,7 +15,7 @@ function M.draw_section(section, section_name, is_focused)
         (type(component) == 'table' and not component.component_no) then
       return '' -- unknown element in section. section posibly not yet loaded
     end
-    table.insert(status, component:draw(highlight_name))
+    table.insert(status, component:draw(highlight_name, is_focused))
   end
 
   -- Flags required for knowing when to remove component separator
@@ -38,7 +38,6 @@ function M.draw_section(section, section_name, is_focused)
                                                    .options.section_separators[1])
         end
       end
-      section[component_no].last_component = true
     end
     -- Remove component separator when color option is used in next component
     if strip_next_component then

lua/lualine/utils/utils.lua

@@ -56,14 +56,23 @@ function M.list_shrink(list)
   return new_list
 end
 
--- Wvaluate a component
-function M.lualine_eval(id, ...)
-  local ok, components = pcall(require, 'lualine.component.components')
-  if ok and components then
-    return components[id]:draw(...)
-  else
-    return ''
+-- Check if a auto command is already defined
+local function autocmd_is_defined(event, patern, command_str)
+  return vim.api.nvim_exec(string.format("au lualine %s %s",
+                           event, patern), true):find(command_str) ~= nil
+end
+
+-- Define a auto command if it's not already defined
+function M.define_autocmd(event, patern, cmd)
+  if not cmd then cmd = patern; patern = '*' end
+  if not autocmd_is_defined(event, patern, cmd) then
+    vim.cmd(string.format("autocmd lualine %s %s %s", event, patern, cmd))
   end
 end
 
+-- Check if statusline is on focused window or not
+function M.is_focused()
+  return tonumber(vim.g.actual_curwin) == vim.fn.win_getid()
+end
+
 return M