Support custom Log4j2 configurations

[alexander-yevsyukov]

What

The Log4j2 backend threw IllegalStateException ("Unable to format a message for the configuration: ...") from LogEvents.toLog4jLogEvent whenever the current Log4j2 configuration was not DefaultConfiguration — i.e., whenever an application provides its own log4j2.xml. This made the backend unusable in any configured application (reported from delivery-server, which packages log4j2.xml in its fat JAR).

The fix

Following the upstream Flogger approach: with a user-provided configuration, only the literal log message becomes the Log4j2 message. The metadata keeps traveling in the log event's context data map (populated by createContextMap()), where a user-defined layout renders it, e.g., via %X. Under DefaultConfiguration, whose hard-wired layout ignores context data, the metadata is still appended to the message itself in the [CONTEXT ... ] form, as before. Spine's LogData carries no template arguments (the Kotlin lambda API evaluates messages before the backend sees them), so Flogger's BaseMessageFormatter branch reduces to the literal message.

The refactoring

The configuration check now reads the configuration of the context owning the logger that renders the event (logger.context.configuration) instead of the statically looked-up LoggerContext.getContext(false). This makes the branch decision consistent with the rendering context in multi-context deployments (per-webapp or OSGi context selectors) and replaces a per-event stack-walking global lookup with a field read. This is a deliberate, documented divergence from the original Flogger implementation. The conversion functions became internal extensions — LogData.toLog4jEvent(logger) and LogData.toLog4jEvent(logger, error); the previous public functions had no external usages.

Testing

• New Log4j2CustomConfigSpec runs against a private, started LoggerContext (no global-state mutation): plain message without the [CONTEXT ... ] suffix, metadata via the context data map, the cause via LogEvent.thrown, and a multi-context test — two backends in one JVM, each formatting per the configuration of its own context.
• Shared test helpers extracted into given/TestLoggers.kt.
• :log4j2-backend:test: 41 tests green; full build and dokkaGenerate pass.
• End-to-end smoke check: with the artifacts published to Maven Local, a Java app using WithLogging and the actual delivery-serverlog4j2.xml on the classpath (XmlConfiguration) logs per the pattern with no exception.

Note for consumers

With a custom configuration, %msg now carries only the log message. To render Spine metadata (tags, key-value context), add %X (e.g., %notEmpty{ [%X]}) to the pattern layout.

Additional changes riding along

Besides the backend work, this branch carries routine housekeeping:

• A config submodule float, which brings the config-distributed updates: buildSrc/** dependency objects, the Gradle wrapper (9.6.1 → 9.7.1), the wrapper-validation workflow, .gitignore, and IDE settings. Per this organization's convention, config-distributed files are reviewed in the config repository, not here.
• Regenerated dependency/license reports under docs/dependencies/.
• Unused-import cleanups in build.gradle.kts and SimpleMessageFormatter.kt.
• The version bump 2.0.0-SNAPSHOT.423 → .424 per the versioning policy.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR updates the Log4j2 backend to work correctly when an application provides a non-DefaultConfiguration (e.g., via log4j2.xml), avoiding runtime failures and ensuring metadata is still available via Log4j2 context data. In addition, the PR includes a substantial set of build/dependency-reporting and dependency/version/tooling updates.

Changes:

• Log4j2 backend: format %msg as the literal message under custom configurations, while keeping metadata in LogEvent context data (and preserving the existing [CONTEXT ...] suffix behavior under DefaultConfiguration).
• Tests: add coverage for custom Log4j2 configuration and multi-context behavior; extract shared test logger helpers.
• Build/dependencies/tooling: version bumps, dependency-reporting changes (POM generation), dependency coordinate updates, and Gradle wrapper/workflow churn.

Reviewed changes

Copilot reviewed 41 out of 46 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
version.gradle.kts	Bumps the published snapshot version.
logging/src/commonMain/kotlin/io/spine/logging/backend/SimpleMessageFormatter.kt	Removes an unused import (no functional change).
gradle/wrapper/gradle-wrapper.properties	Updates the Gradle wrapper distribution URL.
docs/dependencies/pom.xml	Updates the documented/generated dependency POM (versions/coordinates changed).
buildSrc/src/test/kotlin/io/spine/gradle/report/pom/PomGeneratorIgTest.kt	Adds Gradle TestKit-based functional coverage for generatePom.
buildSrc/src/test/kotlin/io/spine/gradle/report/pom/DependencyWriterSpec.kt	Updates dependency writer tests to use resolved-version collection.
buildSrc/src/main/kotlin/io/spine/gradle/report/pom/ResolvedVersions.kt	Introduces per-project resolved-version collection and persistence.
buildSrc/src/main/kotlin/io/spine/gradle/report/pom/PomXmlWriter.kt	Wires resolved versions into POM XML writing.
buildSrc/src/main/kotlin/io/spine/gradle/report/pom/PomGenerator.kt	Makes generatePom depend on per-project resolved-version collectors.
buildSrc/src/main/kotlin/io/spine/gradle/report/pom/DependencyWriter.kt	Refactors dependency collection to take per-project resolved versions.
buildSrc/src/main/kotlin/io/spine/gradle/report/license/LicenseReporter.kt	Adjusts path constants usage and opts license report task out of build cache.
buildSrc/src/main/kotlin/io/spine/dependency/test/Testcontainers.kt	Updates Testcontainers coordinates/version and adds PostgreSQL module.
buildSrc/src/main/kotlin/io/spine/dependency/local/Validation.kt	Bumps Validation version; removes some artifacts.
buildSrc/src/main/kotlin/io/spine/dependency/local/ToolBase.kt	Updates ToolBase version and splits artifacts; deprecates old all-in-one artifact.
buildSrc/src/main/kotlin/io/spine/dependency/local/Time.kt	Bumps Spine Time version.
buildSrc/src/main/kotlin/io/spine/dependency/local/ProtoTap.kt	Bumps ProtoTap version.
buildSrc/src/main/kotlin/io/spine/dependency/local/ModelCompiler.kt	Removes ModelCompiler dependency definition.
buildSrc/src/main/kotlin/io/spine/dependency/local/Logging.kt	Bumps Logging dependency version reference.
buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvmCompiler.kt	Refactors artifact naming and bumps CoreJvmCompiler versions.
buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvm.kt	Bumps CoreJvm version.
buildSrc/src/main/kotlin/io/spine/dependency/local/Compiler.kt	Bumps fallback versions; renames fat CLI artifact; removes CLI API reference.
buildSrc/src/main/kotlin/io/spine/dependency/local/Change.kt	Bumps Spine Change version.
buildSrc/src/main/kotlin/io/spine/dependency/local/BaseTypes.kt	Bumps BaseTypes version.
buildSrc/src/main/kotlin/io/spine/dependency/local/Base.kt	Bumps Spine Base versions.
buildSrc/src/main/kotlin/io/spine/dependency/lib/Roaster.kt	Removes outdated comment about Java 11 compatibility.
buildSrc/src/main/kotlin/io/spine/dependency/lib/PalantirJavaFormat.kt	Bumps Palantir Java Format version.
buildSrc/src/main/kotlin/io/spine/dependency/lib/Log4j2.kt	Bumps Log4j2 version; adds SLF4J 2 bridge coordinate.
buildSrc/src/main/kotlin/io/spine/dependency/lib/JacksonV2.kt	Introduces a dedicated Jackson 2.x BOM/dependency set.
buildSrc/src/main/kotlin/io/spine/dependency/lib/Jackson.kt	Switches Jackson definitions to 3.x (tools.jackson) and updates module declarations.
buildSrc/src/main/kotlin/io/spine/dependency/boms/Boms.kt	Points optional Jackson BOM to Jackson 2.x BOM (via JacksonV2).
buildSrc/src/main/kotlin/BuildExtensions.kt	Adds helper to exclude JetBrains annotations from published deps.
buildSrc/build.gradle.kts	Clarifies buildSrc Jackson pin rationale; configures TestKit and classpath injection.
build.gradle.kts	Removes ToolBase forcing and an exclusion entry.
backends/log4j2-backend/src/test/kotlin/io/spine/logging/backend/log4j2/Log4j2LoggerBackendSpec.kt	Refactors test logger creation to shared helpers.
backends/log4j2-backend/src/test/kotlin/io/spine/logging/backend/log4j2/Log4j2CustomConfigSpec.kt	Adds tests for custom Log4j2 configuration behavior + multi-context check.
backends/log4j2-backend/src/test/kotlin/io/spine/logging/backend/log4j2/given/TestLoggers.kt	Extracts shared test logger/appender utilities.
backends/log4j2-backend/src/main/kotlin/io/spine/logging/backend/log4j2/LogEvents.kt	Implements configuration-aware message formatting and refactors conversion helpers to LogData extensions.
backends/log4j2-backend/src/main/kotlin/io/spine/logging/backend/log4j2/Log4j2LoggerBackend.kt	Updates backend to use the new LogData.toLog4jEvent(...) conversions.
.idea/kotlinc.xml	Removes IDE-local Kotlin compiler settings file.
.gitignore	Clarifies .idea/kotlinc.xml should remain ignored.
.github/workflows/gradle-wrapper-validation.yml	Removes Gradle wrapper validation workflow.
.agents/tasks/log4j2-context-binding.md	Adds an internal task note/document for the Log4j2 context-binding change.
.agents/tasks/custom-log4j2-formatting.md	Adds an internal task note/document for custom Log4j2 formatting support.

Files not reviewed (1)

• .idea/kotlinc.xml: Generated file

Suppressed comments (1)

backends/log4j2-backend/src/main/kotlin/io/spine/logging/backend/log4j2/Log4j2LoggerBackend.kt:51

• Same as above: avoid logger.get() here; log via the logger API directly to avoid relying on the internal get() contract.

 logger.get().log(badData.toLog4jEvent(logger, error))

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[codecov]

Codecov Report

❌ Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 68.67%. Comparing base (584faa2) to head (9b5ecbc).

Additional details and impacted files

@@ Coverage Diff @@## master #149 +/- ##
============================================
+ Coverage 67.80% 68.67% +0.87% - Complexity 464 470 +6 
============================================
Files 109 109 Lines 2578 2586 +8 Branches 403 403 ============================================
+ Hits 1748 1776 +28 + Misses 696 675 -21 - Partials 134 135 +1 

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.