Add support for inline images to mailer previews

Use a preview interceptor to search for inline cid: urls in src
attributes and convert them to data urls.

2 files changed, 10 insertions, 8 deletions

diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index e727509610..3c9de0115f 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -487,13 +487,14 @@ module ApplicationTests
     end
 
     test "plain text mailer preview with attachment" do
-      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioc\na/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJggg=="
+      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
 
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
+            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
             mail to: "to@example.org"
           end
         end
@@ -523,14 +524,14 @@ module ApplicationTests
     end
 
     test "multipart mailer preview with attachment" do
-      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioc\na/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJggg=="
+      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
 
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png")
+            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
             mail to: "to@example.org"
           end
         end
@@ -568,14 +569,14 @@ module ApplicationTests
     end
 
     test "multipart mailer preview with inline attachment" do
-      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioc\na/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJggg=="
+      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
 
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png")
+            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
             mail to: "to@example.org"
           end
         end
@@ -611,6 +612,7 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo?part=text/html"
       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
     end
 
     test "multipart mailer preview with attached email" do
@@ -693,7 +695,7 @@ module ApplicationTests
       end
 
       def image_file(name, contents)
-        app_file("public/images/#{name}", Base64.decode64(contents))
+        app_file("public/images/#{name}", Base64.urlsafe_decode64(contents), 'wb')
       end
   end
 end
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 4509797da1..65d8a55421 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -270,9 +270,9 @@ module TestHelpers
       File.open(file, "w+") { |f| f.puts contents }
     end
 
-    def app_file(path, contents)
+    def app_file(path, contents, mode = 'w')
       FileUtils.mkdir_p File.dirname("#{app_path}/#{path}")
-      File.open("#{app_path}/#{path}", 'w') do |f|
+      File.open("#{app_path}/#{path}", mode) do |f|
         f.puts contents
       end
     end