Ensure Action Mailbox processes an email only once when received multiple times

This also adds a new column, message_checksum, to the action_mailbox_inbound_emails table
for storing SHA1 digest of the email source. Additionally, it makes generating the missing
message id deterministic and adds a unique index on message_checksum and message_id to
detect duplicate emails.

2 files changed, 23 insertions, 2 deletions

diff --git a/actionmailbox/test/unit/inbound_email_test.rb b/actionmailbox/test/unit/inbound_email_test.rb
index 993423406f..76f047eb61 100644
--- a/actionmailbox/test/unit/inbound_email_test.rb
+++ b/actionmailbox/test/unit/inbound_email_test.rb
@@ -11,5 +11,27 @@ module ActionMailbox
     test "source returns the contents of the raw email" do
       assert_equal file_fixture("welcome.eml").read, create_inbound_email_from_fixture("welcome.eml").source
     end
+
+    test "email with message id is processed only once when received multiple times" do
+      mail = Mail.from_source(file_fixture("welcome.eml").read)
+      assert mail.message_id
+
+      inbound_email_1 = create_inbound_email_from_source(mail.to_s)
+      assert inbound_email_1
+
+      inbound_email_2 = create_inbound_email_from_source(mail.to_s)
+      assert_nil inbound_email_2
+    end
+
+    test "email with missing message id is processed only once when received multiple times" do
+      mail = Mail.from_source("Date: Fri, 28 Sep 2018 11:08:55 -0700\r\nTo: a@example.com\r\nMime-Version: 1.0\r\nContent-Type: text/plain\r\nContent-Transfer-Encoding: 7bit\r\n\r\nHello!")
+      assert_nil mail.message_id
+
+      inbound_email_1 = create_inbound_email_from_source(mail.to_s)
+      assert inbound_email_1
+
+      inbound_email_2 = create_inbound_email_from_source(mail.to_s)
+      assert_nil inbound_email_2
+    end
   end
 end
diff --git a/actionmailbox/test/unit/mailbox/routing_test.rb b/actionmailbox/test/unit/mailbox/routing_test.rb
index d4dad7eafb..d4ba702ac5 100644
--- a/actionmailbox/test/unit/mailbox/routing_test.rb
+++ b/actionmailbox/test/unit/mailbox/routing_test.rb
@@ -15,11 +15,10 @@ end
 class ActionMailbox::Base::RoutingTest < ActiveSupport::TestCase
   setup do
     $processed = false
-    @inbound_email = create_inbound_email_from_fixture("welcome.eml")
   end
 
   test "string routing" do
-    ApplicationMailbox.route @inbound_email
+    ApplicationMailbox.route create_inbound_email_from_fixture("welcome.eml")
     assert_equal "Discussion: Let's debate these attachments", $processed
   end