Some incoming mails containing attachment are processed but trigger an error in the Mail Audit Logs

Issue Summary

If an incoming mail meant to create a new Jira issue contains 2 attachments of exact name, the following will happen:

• the Jira issue is successfully created and contains the 2 attachments (note that the filename of one attachment was modified by the mail handler with the extra "-1" at the end)
  
• however, the Mail Processing logs from the page ⚙ > Applications > Email Requests show the error "Unexpected error while running action as user '"
  
• also, the following error is thrown in the Jira application logs:

  2020-06-18 15:08:20,706+0200 Caesium-1-4 ERROR julien     [c.a.p.i.util.runner.AuthenticationContextUtilImpl] Unexpected error while running action as user 'julien'
  java.lang.IllegalStateException: Duplicate key com.atlassian.mail.MailUtils$Attachment@6e4443db
  	at java.util.stream.Collectors.lambda$throwingMerger$0(Collectors.java:133)
  	at java.util.HashMap.merge(HashMap.java:1253)
  	at java.util.stream.Collectors.lambda$toMap$58(Collectors.java:1320)
  	at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169)
  	at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
  	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
  	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
  	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
  	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
  	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
  	at com.atlassian.servicedesk.internal.feature.emailchannel.IncomingEmailManagerImpl.postProcessIssueCreation(IncomingEmailManagerImpl.java:773)
  	at com.atlassian.servicedesk.internal.feature.emailchannel.IncomingEmailManagerImpl.lambda$createIssueInJiraContext$22(IncomingEmailManagerImpl.java:554)
  	at com.atlassian.pocketknife.step.EitherStep4.lambda$null$0(EitherStep4.java:29)
  	at io.atlassian.fugue.Either$RightProjection.flatMap(Either.java:937)
  	at io.atlassian.fugue.Either.flatMap(Either.java:231)
  

Steps to Reproduce

• Install a fresh Service Desk 4.8.0 instance
• Create a Service Desk project
• Configure a Service Desk Mail handler in Project Settings > Email Requests
• Send a new email to the mail handler, including 2 attachments of exact same name
  • Note that the 2 files don't need to have the same content. Only the filename matters to replicate the bug

Expected Results

A new ticket is created from this email and no error is thrown in the Mail Processing logs or Jira log file.

Actual Results

A new ticket is created from this email and an error is thrown in the Mail Processing logs or Jira log file.

Workaround

Workaround 1

Remove any attachment with duplicate file name before sending an email to the Service Desk Mail Handler.

Workaround 2

Disable the dark feature sd.email.attachments.store.duplicates by:

• Going to the page: <JIRA_BASE_URL>/secure/SiteDarkFeatures!default.jspa
• Adding sd.email.attachments.store.duplicates.disabled to the list of dark features, as shown in the screenshot below:
  

Important notes

This bug is similar to the bug JSDSERVER-6884, however:

• the steps to replicate it are different
• the fix implemented for this bug is different than for the other one, therefore the fix version is different for both bugs
• the workaround involving the dark feature only works for this bug, but not for the other one