[ISSUE #10774] Reject empty producer message lists

[Aias00]

What changed

• Reject null or empty producer message lists before building the send context.
• Add regression coverage for both empty and null message list inputs.

Fixes #10774.

Verification

mvn -pl proxy -Dtest=ProducerProcessorTest test

Result: BUILD SUCCESS. ProducerProcessorTest ran 8 tests with 0 failures, errors, or skips. Checkstyle and SpotBugs also passed in the Maven run.

[Copilot]

Pull request overview

This PR adds early validation in the proxy producer send path to reject null/empty message lists (avoiding raw NullPointerException / IndexOutOfBoundsException) and adds regression tests to ensure the failure is surfaced as a controlled ProxyException.

Changes:

• Add a null/empty guard at the start of ProducerProcessor#sendMessage.
• Add regression tests covering both Collections.emptyList() and null message list inputs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
proxy/src/main/java/org/apache/rocketmq/proxy/processor/ProducerProcessor.java	Adds an early guard to reject null/empty messageList before accessing messageList.get(0).
proxy/src/test/java/org/apache/rocketmq/proxy/processor/ProducerProcessorTest.java	Adds tests asserting the returned future completes exceptionally for empty/null message lists.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.27%. Comparing base (eddb235) to head (d21c3e2).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10775      +/-   ##
=============================================
- Coverage      48.34%   48.27%   -0.08%     
+ Complexity     13527    13506      -21     
=============================================
  Files           1380     1380              
  Lines         101104   101143      +39     
  Branches       13107    13121      +14     
=============================================
- Hits           48882    48825      -57     
- Misses         46267    46337      +70     
- Partials        5955     5981      +26     

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[RockteMQ-AI]

Review by github-manager-bot

Summary

Adds null/empty guard for messageList in ProducerActivityManagerImpl.sendMessage() before accessing messageList.get(0), throwing ProxyException with FORBIDDEN instead of risking IndexOutOfBoundsException.

Findings

• [Info] The fix is correct and minimal. Throwing ProxyException with FORBIDDEN is appropriate since sending zero messages is a client error.
• [Info] Test coverage covers both null and empty cases, verifying the correct exception code and message.

Suggestions

• Consider whether other entry points in ProducerActivityManagerImpl that access list elements by index (e.g., sendMessage variants with List<MessageView>) have similar guards. Consistency across the API surface would reduce future NPE/IOOBE risk.

LGTM.

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Automated review by github-manager-bot