update ContentAttachment so that it works with "content" attributes

this makes it possible for an application to embed markup in a document
that would otherwise be undesirable or expensive to process. For example,
an incoming email may include a complicated bit of DOM in a quote, and
while you don't want to have to process and rewrite it, you also don't want
to discard it; the content attribute of ContentAttachment allows you to
make that work.

actiontext/app/views/action_text/attachables/_content_attachment.html.erb

@@ -0,0 +1,3 @@
+<figure class="attachment attachment--content">
+  <%= content_attachment.attachable %>
+</figure>

actiontext/lib/action_text/attachables/content_attachment.rb

@@ -6,33 +6,35 @@ class ContentAttachment
       include ActiveModel::Model
 
       def self.from_node(node)
-        if node["content-type"]
-          if matches = node["content-type"].match(/vnd\.rubyonrails\.(.+)\.html/)
-            attachment = new(name: matches[1])
-            attachment if attachment.valid?
-          end
-        end
+        attachment = new(content_type: node["content-type"], content: node["content"])
+        attachment if attachment.valid?
       end
 
-      attr_accessor :name
-      validates_inclusion_of :name, in: %w( horizontal-rule )
+      attr_accessor :content_type, :content
+
+      validates_format_of :content_type, with: /html/
+      validates_presence_of :content
 
       def attachable_plain_text_representation(caption)
-        case name
-        when "horizontal-rule"
-          " ┄ "
-        else
-          " "
-        end
+        content_instance.fragment.source
+      end
+
+      def to_html
+        @to_html ||= content_instance.render
+      end
+
+      def to_s
+        to_html
       end
 
       def to_partial_path
         "action_text/attachables/content_attachment"
       end
 
-      def to_trix_content_attachment_partial_path
-        "action_text/attachables/content_attachments/#{name.underscore}"
-      end
+      private
+        def content_instance
+          @content_instance ||= ActionText::Content.new(content)
+        end
     end
   end
 end

actiontext/lib/action_text/attachment.rb

@@ -8,7 +8,7 @@ class Attachment
 
     mattr_accessor :tag_name, default: "action-text-attachment"
 
-    ATTRIBUTES = %w( sgid content-type url href filename filesize width height previewable presentation caption )
+    ATTRIBUTES = %w( sgid content-type url href filename filesize width height previewable presentation caption content )
 
     class << self
       def fragment_by_canonicalizing_attachments(content)

actiontext/test/unit/attachment_test.rb

@@ -55,6 +55,20 @@ class ActionText::AttachmentTest < ActiveSupport::TestCase
     assert_equal "[racecar.jpg]", ActionText::Attachment.from_attachable(attachable).to_plain_text
   end
 
+  test "converts HTML content attachment" do
+    attachment = attachment_from_html(%Q(<action-text-attachment content-type="text/html" content="abc"></action-text-attachment>))
+    attachable = attachment.attachable
+
+    assert_kind_of ActionText::Attachables::ContentAttachment, attachable
+    assert_equal "text/html", attachable.content_type
+    assert_equal "abc", attachable.content
+
+    trix_attachment = attachment.to_trix_attachment
+    assert_kind_of ActionText::TrixAttachment, trix_attachment
+    assert_equal "text/html", trix_attachment.attributes["contentType"]
+    assert_equal "abc", trix_attachment.attributes["content"]
+  end
+
   test "defaults trix partial to model partial" do
     attachable = Page.create! title: "Homepage"
     assert_equal "pages/page", attachable.to_trix_content_attachment_partial_path