feat(editorconfig): add support for spelling_language (#28638)

runtime/doc/editorconfig.txt

@@ -78,6 +78,10 @@ root                                                       *editorconfig.root*
     directories. This property must be at the top-level of the `.editorconfig`
     file (i.e. it must not be within a glob section).
 
+spelling_language                             *editorconfig.spelling_language*
+    A code of the format ss or ss-TT, where ss is an ISO 639 language code and
+    TT is an ISO 3166 territory identifier. Sets the 'spelllang' option.
+
 tab_width                                             *editorconfig.tab_width*
     The display size of a single tab character. Sets the 'tabstop' option.
 

runtime/doc/news.txt

@@ -128,7 +128,8 @@ PERFORMANCE
 
 PLUGINS
 
-• TODO
+• EditorConfig
+  • spelling_language property is now supported.
 
 STARTUP
 

runtime/lua/editorconfig.lua

@@ -190,6 +190,27 @@ function properties.insert_final_newline(bufnr, val)
   end
 end
 
+--- A code of the format ss or ss-TT, where ss is an ISO 639 language code and TT is an ISO 3166 territory identifier.
+--- Sets the 'spelllang' option.
+function properties.spelling_language(bufnr, val)
+  local error_msg =
+    'spelling_language must be of the format ss or ss-TT, where ss is an ISO 639 language code and TT is an ISO 3166 territory identifier.'
+
+  assert(val:len() == 2 or val:len() == 5, error_msg)
+
+  local language_code = val:sub(1, 2):lower()
+  assert(language_code:match('%l%l'), error_msg)
+  if val:len() == 2 then
+    vim.bo[bufnr].spelllang = language_code
+  else
+    assert(val:sub(3, 3) == '-', error_msg)
+
+    local territory_code = val:sub(4, 5):lower()
+    assert(territory_code:match('%l%l'), error_msg)
+    vim.bo[bufnr].spelllang = language_code .. '_' .. territory_code
+  end
+end
+
 --- @private
 --- Modified version of [glob2regpat()] that does not match path separators on `*`.
 ---

test/functional/plugin/editorconfig_spec.lua

@@ -16,8 +16,16 @@ local testdir = 'Xtest-editorconfig'
 local function test_case(name, expected)
   local filename = testdir .. pathsep .. name
   command('edit ' .. filename)
+
   for opt, val in pairs(expected) do
+    local opt_info = api.nvim_get_option_info2(opt, {})
+    if opt_info.scope == 'win' then
+      eq(val, api.nvim_get_option_value(opt, { win = 0 }), name)
+    elseif opt_info.scope == 'buf' then
       eq(val, api.nvim_get_option_value(opt, { buf = 0 }), name)
+    else
+      eq(val, api.nvim_get_option_value(opt, {}), name)
+    end
   end
 end
 
@@ -93,6 +101,12 @@ setup(function()
 
     [max_line_length.txt]
     max_line_length = 42
+
+    [short_spelling_language.txt]
+    spelling_language = de
+
+    [long_spelling_language.txt]
+    spelling_language = en-NZ
     ]]
   )
 end)
@@ -222,4 +236,9 @@ But not this one
 
     eq(true, ok, err)
   end)
+
+  it('sets spelllang', function()
+    test_case('short_spelling_language.txt', { spelllang = 'de' })
+    test_case('long_spelling_language.txt', { spelllang = 'en_nz' })
+  end)
 end)