Fix #309: make channelName available in Postprocessor script

[ggiannola]

Summary

Fixes #309. The channelName variable was not available in Postprocessor scripts, even though it is available in Deploy, Undeploy, and Preprocessor scripts.

Root cause

The Postprocessor scope (JavaScriptScopeUtil.getPostprocessorScope) derives channelName from message.getMergedConnectorMessage().getChannelName().

However, Message.getMergedConnectorMessage() built the merged ConnectorMessage setting channelId, messageId, serverId, and receivedDate — but never channelName. The value therefore resolved to null in Postprocessor scripts.

This also explains why the other script contexts were unaffected: they receive the channel name directly (Deploy/Undeploy via getDeployScope/getUndeployScope, Preprocessor from the connector message) rather than through the merged connector message.

Fix

In Message.getMergedConnectorMessage(), populate channelName on the merged connector message:

• from the Message's own channelName field, and
• falling back to the source connector message's channelName, which is reliably set during processing (see the ConnectorMessage construction in Channel).

The fallback matters because the Message created during processing does not always carry channelName, while the source connector message does.

Tests

Added MessageTest covering three cases:

1. The merged message inherits channelName from the source connector message.
2. The merged message uses the Message-level channelName when set.
3. channelName stays null when unavailable, so the fix does not fabricate a value.

Verified with ./gradlew :donkey:test: 21 tests pass, 0 failures (MessageTest 3, StatisticsTest 9, JdbcDaoTest 8, ChannelTest 1).

[pacmano1]

@ggiannola, this works in the post processor.

logger.info(ChannelUtil.getChannelName(channelId))

Not that your PR is "wrong", but based on this trivial workaround it seems unnecessary.

[jonbartels]

Approved.

I have a non-blocking comment - Are there other fields missing from the post-processor?

You found that channelName was missing. Are there other common fields from other scripts that are missing that could also be added in this PR?

[ggiannola]

@ggiannola, this works in the post processor.

logger.info(ChannelUtil.getChannelName(channelId))

Not that your PR is "wrong", but based on this trivial workaround it seems unnecessary.

Thanks @pacmano1 agreed.

Worth noting the postprocessor scope already tries to supply channelName; it was wired in deliberately back in 2015 (2fd0148, MIRTH-1763) and has silently been null ever since because Message.getMergedConnectorMessage() never populated the field. So this is a latent bug rather than a new feature.

It's also broader than the variable, message.getMergedConnectorMessage().getChannelName() is public userutil API and returns null in every postprocessor, which ChannelUtil doesn't address.

4 lines, no API change. But if you'd rather leave it, happy to close.

[github-actions]

Test Results

658 tests  +3   658 ✅ +3   2m 14s ⏱️ + 1m 0s
110 suites +1     0 💤 ±0 
110 files   +1     0 ❌ ±0 

Results for commit c556c59. ± Comparison against base commit 776690e.

♻️ This comment has been updated with latest results.

[pacmano1]

@ggiannola , I'll defer to the other maintainers. I am wishy washy on it, lol.

[tonygermano]

Looks good to me. Thanks for the fix and added tests!