After upgrading my production Redmine to 4.0.0, I encountered a critical problem that I cannot add issue notes by replying emails.

On investigation, it turned out that NoMethodError that is raised at source:tags/4.0.0/app/models/mail_handler.rb#L240 causes the problem.

     # ignore CLI-supplied defaults for new issues
     handler_options[:issue].clear

The code expects that the class of @handler_options[:issue]@ is Hash, however, it is actually ActionController::Parameters. Since the class does not have a "clear" method, the code raises exception and Redmine fails to add the email to the issue note.

The error cannot be detected by running the unit test because the class of @handler_options[:issue]@ is not ActionController::Parameters but Hash in a test environment.

The following is a workaround for this issue.

Index: app/models/mail_handler.rb
===================================================================
--- app/models/mail_handler.rb  (revision 17805)
+++ app/models/mail_handler.rb  (working copy)
@@ -237,7 +237,7 @@
     end

     # ignore CLI-supplied defaults for new issues
-    handler_options[:issue].clear
+    handler_options[:issue] = {}

     journal = issue.init_journal(user)
     if from_journal && from_journal.private_notes?