List inline attachments separately in AM previews

This commit separates inline attachments from normal attachments when
listing attachments in Action Mailer previews.  For example, attachments
that were previously listed like

  > Attachments: logo.png file1.pdf file2.pdf

will now be listed like

  > Attachments: file1.pdf file2.pdf (Inline: logo.png)

Co-authored-by: Jonathan Hefner <[email protected]>

Author: c960657

railties/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   In Action Mailer previews, list inline attachments separately from normal
+    attachments. For example, attachments that were previously listed like
+
+      > Attachments: logo.png file1.pdf file2.pdf
+
+    will now be listed like
+
+      > Attachments: file1.pdf file2.pdf (Inline: logo.png)
+
+    *Christian Schmidt* and *Jonathan Hefner*
+
 *   In mailer preview, only show SMTP-To if it differs from the union of To, Cc and Bcc.
 
     *Christian Schmidt*

railties/lib/rails/mailers_controller.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "rails/application_controller"
+require "active_support/core_ext/enumerable"
 
 class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugView::RESCUES_TEMPLATE_PATHS
@@ -9,7 +10,7 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
   before_action :find_preview, only: [:preview, :download]
   before_action :require_local!, unless: :show_previews?
 
-  helper_method :part_query, :locale_query
+  helper_method :attachment_url, :part_query, :locale_query
 
   content_security_policy(false)
 
@@ -38,6 +39,8 @@ def preview
       if @preview.email_exists?(@email_action)
         @page_title = "Mailer Preview for #{@preview.preview_name}##{@email_action}"
         @email = @preview.call(@email_action, params)
+        @attachments = attachments_for(@email).reject { |filename, attachment| attachment.inline? }
+        @inline_attachments = attachments_for(@email).select { |filename, attachment| attachment.inline? }
 
         if params[:part]
           part_type = Mime::Type.lookup(params[:part])
@@ -95,6 +98,16 @@ def find_part(format) # :doc:
       end
     end
 
+    def attachments_for(email)
+      email.all_parts.to_a.select(&:attachment?).index_by do |attachment|
+        attachment.respond_to?(:original_filename) ? attachment.original_filename : attachment.filename
+      end
+    end
+
+    def attachment_url(attachment)
+      "data:application/octet-stream;charset=utf-8;base64,#{Base64.encode64(attachment.body.to_s)}"
+    end
+
     def part_query(mime_type)
       request.query_parameters.merge(part: mime_type).to_query
     end

railties/lib/rails/templates/rails/mailers/email.html.erb

@@ -98,12 +98,16 @@
     <dt>Subject:</dt>
     <dd><strong id="subject"><%= @email.subject %></strong></dd>
 
-    <% unless @email.attachments.nil? || @email.attachments.empty? %>
+    <% if @attachments.any? || @inline_attachments.any? %>
       <dt>Attachments:</dt>
       <dd>
-        <% @email.attachments.each do |a| %>
-          <% filename = a.respond_to?(:original_filename) ? a.original_filename : a.filename %>
-          <%= link_to filename, "data:application/octet-stream;charset=utf-8;base64,#{Base64.encode64(a.body.to_s)}", download: filename %>
+        <% @attachments.each do |filename, attachment| %>
+          <%= link_to filename, attachment_url(attachment), download: filename %>
+        <% end %>
+
+        <% if @inline_attachments.any? %>
+          (Inline: <% @inline_attachments.each do |filename, attachment| %>
+            <%= link_to filename, attachment_url(attachment), download: filename %><% end %>)
         <% end %>
       </dd>
     <% end %>

railties/test/application/mailer_previews_test.rb

@@ -771,7 +771,10 @@ def foo
 
       get "/rails/mailers/notifier/foo"
       assert_equal 200, last_response.status
-      assert_match %r[<iframe name="messageBody"], last_response.body
+      assert_match %[<iframe name="messageBody"], last_response.body
+      assert_match %[<dt>Attachments:</dt>], last_response.body
+      assert_no_match %[Inline:], last_response.body
+      assert_match %[<a download="pixel.png" href="data:application/octet-stream;charset=utf-8;base64,iVBORw0K], last_response.body
 
       get "/rails/mailers/notifier/foo?part=text/plain"
       assert_equal 200, last_response.status
@@ -819,7 +822,10 @@ def foo
 
       get "/rails/mailers/notifier/foo"
       assert_equal 200, last_response.status
-      assert_match %r[<iframe name="messageBody"], last_response.body
+      assert_match %[<iframe name="messageBody"], last_response.body
+      assert_match %[<dt>Attachments:</dt>], last_response.body
+      assert_no_match %[Inline:], last_response.body
+      assert_match %[<a download="pixel.png" href="data:application/octet-stream;charset=utf-8;base64,iVBORw0K], last_response.body
 
       get "/rails/mailers/notifier/foo?part=text/plain"
       assert_equal 200, last_response.status
@@ -838,7 +844,7 @@ class Notifier < ActionMailer::Base
           default from: "[email protected]"
 
           def foo
-            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
+            attachments.inline['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "[email protected]"
           end
         end
@@ -865,7 +871,9 @@ def foo
 
       get "/rails/mailers/notifier/foo"
       assert_equal 200, last_response.status
-      assert_match %r[<iframe name="messageBody"], last_response.body
+      assert_match %[<iframe name="messageBody"], last_response.body
+      assert_match %[<dt>Attachments:</dt>], last_response.body
+      assert_match %r[\(Inline:\s+<a download="pixel.png" href="data:application/octet-stream;charset=utf-8;base64,iVBORw0K], last_response.body
 
       get "/rails/mailers/notifier/foo?part=text/plain"
       assert_equal 200, last_response.status
@@ -875,6 +883,10 @@ def foo
       assert_equal 200, last_response.status
       assert_match %r[<p>Hello, World!</p>], last_response.body
       assert_match %r[src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="], last_response.body
+
+      get "/rails/mailers/download/notifier/foo"
+      email = Mail.read_from_string(last_response.body)
+      assert_equal "inline; filename=pixel.png", email.attachments.inline["pixel.png"].content_disposition
     end
 
     test "multipart mailer preview with attached email" do
@@ -923,7 +935,10 @@ def foo
 
       get "/rails/mailers/notifier/foo"
       assert_equal 200, last_response.status
-      assert_match %r[<iframe name="messageBody"], last_response.body
+      assert_match %[<iframe name="messageBody"], last_response.body
+      assert_match %[<dt>Attachments:</dt>], last_response.body
+      assert_no_match %[Inline:], last_response.body
+      assert_match %[<a download="message.eml" href="data:application/octet-stream;charset=utf-8;base64,RGF0ZTog], last_response.body
 
       get "/rails/mailers/notifier/foo?part=text/plain"
       assert_equal 200, last_response.status