Use `Mime[:foo]` instead of `Mime::Type[:FOO]` for back compat

Rails 4.x and earlier didn't support `Mime::Type[:FOO]`, so libraries
that support multiple Rails versions would've had to feature-detect
whether to use `Mime::Type[:FOO]` or `Mime::FOO`.

`Mime[:foo]` has been around for ages to look up registered MIME types
by symbol / extension, though, so libraries and plugins can safely
switch to that without breaking backward- or forward-compatibility.

Note: `Mime::ALL` isn't a real MIME type and isn't registered for lookup
by type or extension, so it's not available as `Mime[:all]`. We use it
internally as a wildcard for `respond_to` negotiation. If you use this
internal constant, continue to reference it with `Mime::ALL`.

Ref. efc6dd550ee49e7e443f9d72785caa0f240def53

3 files changed, 3 insertions, 3 deletions

diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index e506c782d6..fa46a22500 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -136,7 +136,7 @@ module ActionView
         tag(
           "link",
           "rel"   => tag_options[:rel] || "alternate",
-          "type"  => tag_options[:type] || Mime::Type.lookup_by_extension(type.to_s).to_s,
+          "type"  => tag_options[:type] || Mime[type].to_s,
           "title" => tag_options[:title] || type.to_s.upcase,
           "href"  => url_options.is_a?(Hash) ? url_for(url_options.merge(:only_path => false)) : url_options
         )
diff --git a/actionview/test/actionpack/controller/render_test.rb b/actionview/test/actionpack/controller/render_test.rb
index 9409775fef..bdb9e0397b 100644
--- a/actionview/test/actionpack/controller/render_test.rb
+++ b/actionview/test/actionpack/controller/render_test.rb
@@ -466,7 +466,7 @@ class TestController < ApplicationController
   end
 
   def render_content_type_from_body
-    response.content_type = Mime::RSS
+    response.content_type = Mime[:rss]
     render body: "hello world!"
   end
 
diff --git a/actionview/test/template/lookup_context_test.rb b/actionview/test/template/lookup_context_test.rb
index 1184cf7da8..2e3a3f9bae 100644
--- a/actionview/test/template/lookup_context_test.rb
+++ b/actionview/test/template/lookup_context_test.rb
@@ -52,7 +52,7 @@ class LookupContextTest < ActiveSupport::TestCase
   end
 
   test "handles explicitly defined */* formats fallback to :js" do
-    @lookup_context.formats = [:js, Mime::Type[:ALL]]
+    @lookup_context.formats = [:js, Mime::ALL]
     assert_equal [:js, *Mime::SET.symbols], @lookup_context.formats
   end