|DEPRECATION| enhance(themes): Auto colorscheme detection and more

- `auto` theme now auto loads available theme for colorschme based on
  g:color_name . If that fails then it generates a theme for that
  colorschme like before.
- Theme from external source is preferred over bundled version in
  lualine . This means if user has a colorschme that provided the same
  theme as lualine the one from colorschme will be loaded.
- Default value of theme is changed to `auto` from `gruvbox`.
- Now when users theme from config fails lualine will fallbavk to
  `auto`. If `auto` fails then lualine will fallback to `gruvbox`
- Some themes have been renamed to their actual name (g:color_name).
  older names have been deprecated. [DEPRECATION]
    oceanicnext -> OceanicNext
    papercolor -> PaperColor
    tomorrow -> Tomorrow
    gruvbox_material -> gruvbox-material
    modus_vivendi -> modus-vivendi
- A few more adaptive themes added (aye, gruvbox, iceberg)
- Updated THEMES.md to reflect changes in theme name

THEMES.md

@@ -37,6 +37,10 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648541-cbb0cc80-74bb-11eb-843f-19c4c58b1d91.png'/>
 </p>
 
+### ayu
+It's a combination of ayu_light, ayu_dark & ayu_mirage. It loads one of these
+them based you your `g:ayucolor` option.
+
 ### codedark
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648568-dff4c980-74bb-11eb-9d16-b68ac68f2ab2.png'/>
@@ -61,7 +65,7 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648675-22b6a180-74bc-11eb-9b8e-45e64a03e062.png'/>
 </p>
 
-### gruvbox
+### gruvbox_dark
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648685-2b0edc80-74bc-11eb-9ec9-9aac3677df43.png'/>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648693-2ea26380-74bc-11eb-831a-9ebbe4f3dd83.png'/>
@@ -77,7 +81,11 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/34294427/118757020-5ffdb600-b896-11eb-95e7-dbf1f08e063d.png'/>
 </p>
 
-### gruvbox_material
+### gruvbox
+It's a combination of gruvbox_light and gruvbox_dark. It loads either of
+them based you your `background` option.
+
+### gruvbox-material
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648725-3f52d980-74bc-11eb-8fa5-a77b0a21cdea.png'/>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648728-41b53380-74bc-11eb-99cf-001eab6cc51b.png'/>
@@ -109,6 +117,10 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648862-7aeda380-74bc-11eb-808c-1b12dde45f3d.png'/>
 </p>
 
+### iceberg
+It's a combination of icrberg_light and icrberg_dark. It loads either of
+them based you your `background` option.
+
 ### jellybeans
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648882-82ad4800-74bc-11eb-91e8-4d38fcdec134.png'/>
@@ -125,7 +137,7 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108648935-a2dd0700-74bc-11eb-9a4b-72eb1e2ab79e.png'/>
 </p>
 
-### modus_vivendi
+### modus-vivendi
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/9327361/114389966-58176b80-9b9e-11eb-944e-1e0079527d74.png'/>
 <img width='700' src='https://user-images.githubusercontent.com/9327361/114390000-606fa680-9b9e-11eb-97dd-ef5bbc23049a.png'/>
@@ -157,7 +169,7 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649021-cf911e80-74bc-11eb-8b4a-9f9eb61c7973.png'/>
 </p>
 
-### oceanicnext
+### OceanicNext
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649039-d7e95980-74bc-11eb-9a33-df413936c645.png'/>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649043-d91a8680-74bc-11eb-9b1b-9c2e88ede3aa.png'/>
@@ -205,6 +217,10 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649137-0cf5ac00-74bd-11eb-8764-765bead5de6e.png'/>
 </p>
 
+### PaperColor
+It's a combination of papercolor_light and papercolor_dark. It loads either of
+them based you your `background` option.
+
 ### powerline
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649147-14b55080-74bd-11eb-9670-713185342eb2.png'/>
@@ -237,7 +253,7 @@ lualine try to match your colorscheme.
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649258-48907600-74bd-11eb-9bba-8e82b56777d9.png'/>
 </p>
 
-### tomorrow
+### Tomorrow
 <p>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649275-51814780-74bd-11eb-881b-1e137a0cbfe0.png'/>
 <img width='700' src='https://user-images.githubusercontent.com/41551030/108649297-59d98280-74bd-11eb-92a5-a8c4af150106.png'/>

lua/lualine/config.lua

@@ -3,7 +3,7 @@
 local config = {
   options = {
     icons_enabled = true,
-    theme = 'gruvbox',
+    theme = 'auto',
     component_separators = {'', ''},
     section_separators = {'', ''},
     disabled_filetypes = {}

lua/lualine/init.lua

@@ -171,20 +171,74 @@ end
 
 local function tabline() return statusline(config.tabline, true) end
 
+local function check_theme_name_deprecation(theme_name)
+  local deprection_table = {
+    oceanicnext      = 'OceanicNext',
+    papercolor       = 'PaperColor',
+    tomorrow         = 'Tomorrow',
+    gruvbox_material = 'gruvbox-material',
+    modus_vivendi    = 'modus-vivendi',
+  }
+  if deprection_table[theme_name] then
+    local correct_name = deprection_table[theme_name]
+    utils_notices.add_notice(string.format([[
+### options.theme
+You're using `%s` as theme name .
+It has recently been renamed to `%s`.
+Please update your config to follow that.
+
+You have something like this in your config.
+```lua
+options = {
+  theme = '%s'
+}
+```
+
+You'll have to change it to something like this.
+```lua
+options = {
+  theme = '%s'
+}
+```
+
+]], theme_name, correct_name, theme_name, correct_name))
+    return  correct_name
+  end
+  return theme_name
+end
+
+local function notify_theme_error(theme_name)
+  local message_template = theme_name ~= 'auto' and [[
+### options.theme
+Theme `%s` not found, falling back to `auto`. Check if spelling is right.
+]] or [[
+### options.theme
+Theme `%s` failed, falling back to `gruvbox`.
+This shouldn't happen.
+Please report the issue at https://github.com/shadmansaleh/lualine.nvim/issues .
+Also provide what colorscheme you're using.
+]]
+  utils_notices.add_notice(string.format(message_template, theme_name))
+end
+
 local function setup_theme()
   local function get_theme_from_config()
     local theme_name = config.options.theme
     if type(theme_name) == 'string' then
-      package.loaded['lualine.themes.'..theme_name] = nil
-      local ok, theme = pcall(require, 'lualine.themes.' .. theme_name)
-      if ok then return theme end
+      theme_name = check_theme_name_deprecation(theme_name)
+      local ok, theme = pcall(loader.load_theme, theme_name)
+      if ok and theme then return theme end
     elseif type(theme_name) == 'table' then
       -- use the provided theme as-is
       return config.options.theme
     end
-    vim.api.nvim_err_writeln('theme ' .. tostring(theme_name) ..
-                                 ' not found, defaulting to gruvbox')
-    return require 'lualine.themes.gruvbox'
+    if theme_name ~= 'auto' then
+      notify_theme_error(theme_name)
+      local ok, theme = pcall(loader.load_theme, 'auto')
+      if ok and theme then return theme end
+    end
+    notify_theme_error('auto')
+    return loader.load_theme('gruvbox')
   end
   local theme = get_theme_from_config()
   highlight.create_highlight_groups(theme)

lua/lualine/themes/auto.lua

@@ -1,4 +1,13 @@
 local utils = require 'lualine.utils.utils'
+local loader = require 'lualine.utils.loader'
+
+local color_name  = vim.g.colors_name
+if color_name then
+  -- Check if there's a theme for current colorscheme
+  -- If there is load that instead of genarating a new one
+  local ok, theme = pcall(loader.load_theme, color_name)
+  if ok and theme then return theme end
+end
 
 ---------------
 -- Constents --

lua/lualine/themes/ayu.lua

@@ -0,0 +1,7 @@
+-- Copyright (c) 2020-2021 shadmansaleh
+-- MIT license, see LICENSE for more details.
+-- Credit: itchyny(lightline)
+-- License: MIT License
+local style = vim.g.ayucolor or 'dark'
+
+return require('lualine.themes.ayu_' .. style)

lua/lualine/themes/gruvbox.lua

@@ -1,48 +1,7 @@
--- Copyright (c) 2020-2021 hoob3rt
+-- Copyright (c) 2020-2021 shadmansaleh
 -- MIT license, see LICENSE for more details.
--- LuaFormatter off
-local colors = {
-  black        = '#282828',
-  white        = '#ebdbb2',
-  red          = '#fb4934',
-  green        = '#b8bb26',
-  blue         = '#83a598',
-  yellow       = '#fe8019',
-  gray         = '#a89984',
-  darkgray     = '#3c3836',
-  lightgray    = '#504945',
-  inactivegray = '#7c6f64',
-}
--- LuaFormatter on
-return {
-  normal = {
-    a = {bg = colors.gray, fg = colors.black, gui = 'bold'},
-    b = {bg = colors.lightgray, fg = colors.white},
-    c = {bg = colors.darkgray, fg = colors.gray}
-  },
-  insert = {
-    a = {bg = colors.blue, fg = colors.black, gui = 'bold'},
-    b = {bg = colors.lightgray, fg = colors.white},
-    c = {bg = colors.lightgray, fg = colors.white}
-  },
-  visual = {
-    a = {bg = colors.yellow, fg = colors.black, gui = 'bold'},
-    b = {bg = colors.lightgray, fg = colors.white},
-    c = {bg = colors.inactivegray, fg = colors.black}
-  },
-  replace = {
-    a = {bg = colors.red, fg = colors.black, gui = 'bold'},
-    b = {bg = colors.lightgray, fg = colors.white},
-    c = {bg = colors.black, fg = colors.white}
-  },
-  command = {
-    a = {bg = colors.green, fg = colors.black, gui = 'bold'},
-    b = {bg = colors.lightgray, fg = colors.white},
-    c = {bg = colors.inactivegray, fg = colors.black}
-  },
-  inactive = {
-    a = {bg = colors.darkgray, fg = colors.gray, gui = 'bold'},
-    b = {bg = colors.darkgray, fg = colors.gray},
-    c = {bg = colors.darkgray, fg = colors.gray}
-  }
-}
+-- Credit: itchyny(lightline)
+-- License: MIT License
+local background = vim.opt.background:get()
+
+return require('lualine.themes.gruvbox_' .. background)

lua/lualine/themes/gruvbox_dark.lua

@@ -0,0 +1,48 @@
+-- Copyright (c) 2020-2021 hoob3rt
+-- MIT license, see LICENSE for more details.
+-- LuaFormatter off
+local colors = {
+  black        = '#282828',
+  white        = '#ebdbb2',
+  red          = '#fb4934',
+  green        = '#b8bb26',
+  blue         = '#83a598',
+  yellow       = '#fe8019',
+  gray         = '#a89984',
+  darkgray     = '#3c3836',
+  lightgray    = '#504945',
+  inactivegray = '#7c6f64',
+}
+-- LuaFormatter on
+return {
+  normal = {
+    a = {bg = colors.gray, fg = colors.black, gui = 'bold'},
+    b = {bg = colors.lightgray, fg = colors.white},
+    c = {bg = colors.darkgray, fg = colors.gray}
+  },
+  insert = {
+    a = {bg = colors.blue, fg = colors.black, gui = 'bold'},
+    b = {bg = colors.lightgray, fg = colors.white},
+    c = {bg = colors.lightgray, fg = colors.white}
+  },
+  visual = {
+    a = {bg = colors.yellow, fg = colors.black, gui = 'bold'},
+    b = {bg = colors.lightgray, fg = colors.white},
+    c = {bg = colors.inactivegray, fg = colors.black}
+  },
+  replace = {
+    a = {bg = colors.red, fg = colors.black, gui = 'bold'},
+    b = {bg = colors.lightgray, fg = colors.white},
+    c = {bg = colors.black, fg = colors.white}
+  },
+  command = {
+    a = {bg = colors.green, fg = colors.black, gui = 'bold'},
+    b = {bg = colors.lightgray, fg = colors.white},
+    c = {bg = colors.inactivegray, fg = colors.black}
+  },
+  inactive = {
+    a = {bg = colors.darkgray, fg = colors.gray, gui = 'bold'},
+    b = {bg = colors.darkgray, fg = colors.gray},
+    c = {bg = colors.darkgray, fg = colors.gray}
+  }
+}

lua/lualine/themes/iceberg.lua

@@ -0,0 +1,7 @@
+-- Copyright (c) 2020-2021 shadmansaleh
+-- MIT license, see LICENSE for more details.
+-- Credit: itchyny(lightline)
+-- License: MIT License
+local background = vim.opt.background:get()
+
+return require('lualine.themes.iceberg_' .. background)

lua/lualine/utils/loader.lua

@@ -75,4 +75,24 @@ local function load_all(config)
   load_extensions(config)
 end
 
-return {load_all = load_all}
+local function load(patern)
+  local files = vim.fn.uniq(vim.api.nvim_get_runtime_file(patern, true))
+  local n_files = #files
+  if n_files == 0 then return nil
+  elseif n_files == 1 then return  dofile(files[1])
+  else
+    for _, file in ipairs(files) do
+      if not file:find('lualine.nvim') then return dofile(file) end
+    end
+  end
+end
+
+local function load_theme(theme_name)
+  return load(table.concat(
+               {'lua', 'lualine', 'themes', theme_name..'.lua'}, package.config:sub(1, 1)))
+end
+
+return {
+  load_all = load_all,
+  load_theme = load_theme
+}

lua/tests/spec/config_spec.lua

@@ -19,7 +19,7 @@ describe('config parsing', function()
     describe('theme', function()
       it('default', function()
         local config = config_module.apply_configuration({})
-        eq(config.options.theme, 'gruvbox')
+        eq(config.options.theme, 'auto')
       end)
       it('custom', function()
         local config = {options = {theme = 'nord'}}