gnodet opened a new pull request, #12694:
URL: https://github.com/apache/maven/pull/12694
## Summary
Focused, reviewable PR that lays the logging infrastructure foundation for
the build report work (#12572). Split out from #12572 to enable focused review
and discussion of the logging architecture.
### What's included
**Log API enhancements** (`maven-api-core`)
- `Log.trace()` — 5 overloads + `isTraceEnabled()` to separate Maven core
internals (trace) from user-facing debug output (debug). Maps to SLF4J TRACE /
JUL FINEST.
- `Log.child(name)` — hierarchical sub-loggers for plugins that want to
separate concerns while keeping level control. Default implementation returns
`this` for backward compatibility.
**Structured LogEvent** (`maven-api-core`, `maven-core`)
- `LogEvent` / `LogLevel` API for structured log event representation
- Optional JUL metadata fields: `sourceClassName()`, `sourceMethodName()`,
`threadId()` — populated only for events originating from `java.util.logging`,
`null` for SLF4J/Log API events
**Custom JUL Handler** (`maven-logging`)
- `MavenJulHandler` replaces `SLF4JBridgeHandler` — reimplements JUL→SLF4J
bridging while preserving the full `LogRecord` metadata that the standard
bridge silently drops
- Uses a ThreadLocal to pass JUL metadata synchronously to
`ProjectBuildLogAppender` during the same `publish()` call
- Three code paths, one pipeline: Log API → SLF4J, SLF4J direct, JUL →
`MavenJulHandler` → SLF4J — all converge on the same structured `LogEvent`
**Structured LogSink** (`maven-logging`, `maven-core`)
- `MavenSimpleLogger.LogSink` — structured callback with `(level,
loggerName, cleanMessage, formattedMessage, throwable)` replacing the old
`Consumer<String>` sink
- `ProjectBuildLogAppender` produces `LogEvent` objects (with JUL metadata
when available) instead of raw strings
- `BuildEventListener.projectLogMessage()` now takes `LogEvent` instead of
`String`
**Mojo MDC & logger name** (`maven-core`)
- `maven.mojo.id` MDC key set during mojo execution (format:
`prefix:goal@executionId`)
- Logger name changed from `getFullGoalName()` ("compiler:compile") to
`getImplementation()` (FQCN like
`org.apache.maven.plugins.compiler.CompilerMojo`) for proper hierarchical SLF4J
level configuration
**Bug fix**
- `DefaultLog.warn(Supplier<String>, Throwable)` was calling `logger.info()`
instead of `logger.warn()`
### Context
This is Part 1 of the #12572 split. The build report, console modes, and
warning mode features will follow as separate PRs on top of this foundation.
See discussion in the [dev@ thread](https://lists.apache.org/thread/...) and
Martin's feedback on JUL field preservation.
### Depends on / blocks
- Blocks: #12572 (remaining build report features)
- Related: #12690 (4.0.x backport of Log API changes)
- Related: apache/maven-compiler-plugin#1101 (compiler plugin using Log API)
## Test plan
- [x] `mvn test -pl impl/maven-core,impl/maven-logging` — 580 tests pass
- [ ] Full CI validation
- [ ] IT suite with JUL-using plugins (verify metadata preservation)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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