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

2 files changed, 3 insertions, 3 deletions

diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 38004fe99a..6143cf2dd9 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -31,7 +31,7 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
             raise AbstractController::ActionNotFound, "Email part '#{part_type}' not found in #{@preview.name}##{@email_action}"
           end
         else
-          @part = find_preferred_part(request.format, Mime::Type[:HTML], Mime::Type[:TEXT])
+          @part = find_preferred_part(request.format, Mime[:html], Mime[:text])
           render action: 'email', layout: false, formats: %w[html]
         end
       else
diff --git a/railties/lib/rails/templates/rails/mailers/email.html.erb b/railties/lib/rails/templates/rails/mailers/email.html.erb
index cf95cd8ad0..3adc51b568 100644
--- a/railties/lib/rails/templates/rails/mailers/email.html.erb
+++ b/railties/lib/rails/templates/rails/mailers/email.html.erb
@@ -95,8 +95,8 @@
     <% if @email.multipart? %>
       <dd>
         <select onchange="document.getElementsByName('messageBody')[0].src=this.options[this.selectedIndex].value;">
-          <option <%= request.format == Mime::Type[:HTML] ? 'selected' : '' %> value="?part=text%2Fhtml">View as HTML email</option>
-          <option <%= request.format == Mime::Type[:TEXT] ? 'selected' : '' %> value="?part=text%2Fplain">View as plain-text email</option>
+          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="?part=text%2Fhtml">View as HTML email</option>
+          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="?part=text%2Fplain">View as plain-text email</option>
         </select>
       </dd>
     <% end %>