Forward-port: Log API enhancements and mojo MDC - #12929
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* Backport Log API enhancements and mojo MDC to 4.0.x
Backport four Log-related improvements from master to the 4.0.x branch
for inclusion in rc-7:
1. Log.trace() — new trace level (maps to SLF4J TRACE / JUL FINEST)
to separate Maven core internals from user-facing debug messages.
Currently -X floods debug output with resolver/interpolation details
that drown user-relevant diagnostics.
2. Log.child(name) — creates a sub-logger with an independently
filterable name (e.g. "CompilerMojo.diagnostics"), letting plugin
sub-components log under their own namespace.
3. Logger name alignment — Maven 4 Log now uses the mojo implementation
class name (e.g. "org.apache.maven.plugins.compiler.CompilerMojo")
instead of the goal name ("compiler:compile"). This matches what
Maven 3 mojos already use and enables standard SLF4J hierarchical
level configuration.
4. Mojo MDC propagation — sets "maven.mojo.id" (prefix:goal@executionId)
in the SLF4J MDC during mojo execution. All log messages — including
those arriving through the JUL-to-SLF4J bridge — now carry mojo
context, available to any SLF4J appender via %X{maven.mojo.id}.
Also fixes a pre-existing bug in DefaultLog where warn(Supplier, Throwable)
incorrectly delegated to logger.info() instead of logger.warn().
Co-Authored-By: Claude Opus 4.6 <[email protected]>
* Add isXxxEnabled() guards to Throwable-only log overloads
Align with master by wrapping the five xxx(Throwable) overloads
in level-enabled checks, avoiding unnecessary method calls and
empty string construction when the level is disabled.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
* Address review: default trace methods and fork-aware mojoId
Apply review fixes from #12694 to align the backport:
- Log.java: make all 6 trace methods default (no-ops) to prevent
AbstractMethodError for existing third-party Log implementors.
isTraceEnabled() returns false by default.
- ProjectBuildLogAppender: add FORKING_MOJO_ID ThreadLocal mirroring
the existing FORKING_PROJECT_ID pattern. When setMojoId(null) is
called, the forking mojo's ID is restored instead of clearing.
- LoggingExecutionListener: save current mojoId in forkStarted(),
clear forking mojoId in forkSucceeded/forkFailed. Fix cleanup
ordering in mojoSucceeded/mojoFailed — delegate runs first, then
MDC is cleared.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
* Address review: add DefaultLogTest and clear MDC on mojoSkipped
- Add DefaultLogTest with 5 tests: warn/supplier regression,
trace delegation, trace no-op guard, child() sub-logger,
and default trace methods (AbstractMethodError prevention).
- Clear mojo MDC in mojoSkipped() to prevent stale mojo context
from leaking into subsequent log messages.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
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Co-authored-by: Claude Opus 4.6 <[email protected]>
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gnodet
commented
Aug 30, 2026
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Clean forward-port of #12690 from maven-4.0.x to master. The diff is byte-identical to the merged PR — no adaptation was needed. All findings from 4 prior review rounds on #12690 have been addressed.
Observations (informational):
- Cherry-pick applied with zero conflicts; both diffs are 617 lines and byte-identical
- Other
Logimplementations on master (MojoLogWrapper, compatDefaultLog,SystemStreamLog) implement the legacyorg.apache.maven.plugin.logging.Log, notorg.apache.maven.api.plugin.Log, so they are unaffected by the newtrace/childdefault methods - The
getFullGoalName()→getImplementation()change is consistent with existing usage inDefaultMavenPluginManager.javawhich already usesgetImplementation()for the mojo logger - PR description accurately documents the relationship with #12694 which will add master-only additions
📋 PR Metadata
| Aspect | Current | Suggested |
|---|---|---|
| Labels | (none) | enhancement |
| Milestone | (none) | 4.1.0 |
This review was generated by an AI agent and may contain inaccuracies. Please verify all suggestions before applying.
Claude Code on behalf of Guillaume Nodet
elharo
reviewed
Aug 30, 2026
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| /** | ||
| * Sends a message to the user in the <b>trace</b> error level. |
Contributor
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usually written as "at the trace error level" rather than "in the trace error level"
| * such as resolver negotiation, model interpolation, and lifecycle | ||
| * ordering details. Use {@link #debug(CharSequence)} instead for | ||
| * messages that help <em>users</em> investigate their build | ||
| * (e.g. why a module was recompiled). |
- "in the trace error level" → "at the trace error level" - "e.g." → "for instance," Co-Authored-By: Claude Opus 4.6 <[email protected]>
|
@gnodet Please assign appropriate label to PR according to the type of change. |
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Summary
Forward-port of #12690 (merged into
maven-4.0.x) tomaster.Brings the following Log API enhancements to master:
Log.trace()— new trace level (SLF4J TRACE) withdefaultno-op implementations to preventAbstractMethodErrorfor existing third-partyLogimplementorsLog.child(name)— creates a sub-logger with an independently filterable hierarchical namemaven.mojo.idin SLF4J MDC during mojo execution, fork-aware (saves/restores across forked lifecycles)DefaultLog.warn(Supplier, Throwable)was delegating tologger.info()instead oflogger.warn()isXxxEnabled()guards — added toThrowable-only log overloadsDefaultLogTest— 5 new tests covering trace delegation, warn bug fix, child loggers, and backward compatibilityOnce this merges, #12694 will be rebased on top to layer the master-only additions (structured
LogEvent, JUL handler,LogSink,withMetadata/StackWalker).Related
maven-4.0.x, milestone 4.1.0)Test plan
🤖 Generated with Claude Code