Build Report Foundation — structured report, console modes, warning control

[gnodet]

Summary

Implements the build output overhaul proposed in #12571: a structured BuildReport data model with JSON persistence, a DiagnosticCollector for deduplicated warning summaries, four --console modes (plain, rich, machine, verbose), a --warning-mode CLI flag, automatic Log.warn() interception for Maven 3 plugin warnings, per-key diagnostic suppression, and a mvnlog build report viewer.

What's included

Structured Build Report

• BuildReport → ModuleReport → MojoReport data model in maven-api-core with id() and findModule()/findMojo() lookup methods
• Per-mojo and per-module log capture using structured LogEvent
• FailureReport with timestamp, exception type, and stack trace
• BuildReportCollector (EventSpy, @Named @Singleton) — captures lifecycle events
• BuildReportJsonWriter — hand-written JSON serializer (no library dependency)
• Persists target/build-reports/build-report-latest.json at session end, with timestamped history
• API lives in org.apache.maven.api.build.report sub-package

DiagnosticCollector + Warning Summary

• Diagnostic / DiagnosticCollector / DiagnosticSummary API
• DefaultDiagnosticCollector — thread-safe (ConcurrentHashMap + LongAdder), dedup by key, capped at 1000
• Deduplicated warning summary printed at end of build with counts, suggestions, doc URLs
• Diagnostics written to build-report.json

Console Modes (--console)

Flag	Behavior
--console=auto (default)	CI → plain; TTY → rich; otherwise → verbose
--console=plain	One line per module, no ANSI — auto-selected in CI
--console=rich	JLine status bar with live reactor progress, parallel-build aware
--console=verbose	Full mojo-level output (Maven 4.0 default)
--console=machine	JSON lines — one typed event per line, designed for tools and LLM agents

Plain mode: compact footer, no ANSI control sequences.
Rich mode: live Display bar showing active modules, [n/total] progress, elapsed time, download progress. All output bypasses SLF4J (routed through BuildEventListener.log()) to avoid the ProjectBuildLogAppender filter chain. Warning/error counts are tracked and shown in the compact end-of-build summary. Falls back gracefully on dumb terminals.
Machine mode: one JSON object per line with typed "event" field and ISO-8601 timestamps. Events: build.started/finished, module.started/succeeded/failed/skipped, mojo.*, fork.*, transfer.*.

Warning Mode, Log Interception, Diagnostic Suppression

Flag	Behavior
--warning-mode=summary (default)	Collect and show deduplicated summary at end
--warning-mode=all	Show inline + summary
--warning-mode=none	Suppress diagnostic summary
--warning-mode=fail	Show summary + fail build if warnings exist

• Log.warn() interception — auto-feeds Maven 3 plugin WARN-level output into DiagnosticCollector via synthetic dedup keys (auto:<LoggerSuffix>:<hexHash>), with file-coordinate stripping so the same warning from different files deduplicates
• -Dmaven.diagnostic.suppress=<key> — suppress diagnostics by exact key or prefix wildcard (auto:*)

Version Info on Failure (MNG-7372)

On BUILD FAILURE, all console modes now display the Maven version and Java version/vendor in the summary. This helps with bug reports and Stack Overflow questions where java -version output may not match the JDK Maven actually used.

Build Report Viewer (mvnlog)

A lightweight tool to view previous build reports without running a full Maven build or an external plugin. Available in two forms:

• Standalone command: mvnlog (or mvn --log) — skips DI container setup for fast startup
• Shell subcommand: mvnlog inside mvnsh — shares the shell session context

Flag	Behavior
(no flag)	Summary view — status, module table, timing, warning/failure counts
--diagnostics / -d	Detailed warnings and errors from the build
--failures / -f	Detailed failure information including stack traces
--full / -F	Full per-module, per-mojo timing breakdown
--list / -L	List all available build reports in target/build-reports/

Positional argument accepts a path to a specific report file; defaults to target/build-reports/build-report-latest.json.

Key implementation details:

• LogInvoker extends LookupInvoker but overrides doInvoke() to skip the heavyweight DI container, settings, and repository setup
• SimpleJsonReader — zero-dependency recursive descent JSON parser (matches the zero-dependency spirit of BuildReportJsonWriter)
• BuildReportRenderer — shared rendering logic between standalone and mvnsh subcommand via Consumer<String> output pattern
• LogOptions API interface with CommonsCliLogOptions CLI parsing
• Shell wrapper scripts (mvnlog / mvnlog.cmd) for Unix and Windows

Shell Script Routing-Flag Fix

The mvn / mvn.cmd launcher scripts now strip routing flags (--debug, --yjp, --enc, --shell, --up, --log) from the argument list before invoking Java. Previously these flags were consumed by handle_args() to set MAVEN_MAIN_CLASS but still passed through in $@/%*, where Commons CLI's partial long-option matching would collide (e.g. --log prefix-matched --log-file, causing mvnlog --help to crash).

What's NOT included (separate work)

• Core plugin migration (maven-compiler-plugin, maven-enforcer-plugin, maven-surefire-plugin, maven-dependency-plugin reporting structured Diagnostic objects)

Tests

74 unit tests across 12 test classes covering report assembly, JSON serialization, diagnostic dedup/suppression/concurrency, all console modes, warning modes, SLF4J bypass verification, warning summary display, version-on-failure behavior, JSON parsing, and build report rendering.

12 integration tests (MavenITgh12571BuildReportTest) covering end-to-end behavior:

• Build report JSON generation (single-module and multi-module)
• Console modes: plain, machine, verbose, auto with CI=true
• Warning mode: --warning-mode=none suppresses diagnostics
• Version info displayed on build failure
• mvnlog viewer: summary view, --full per-module detail, --list reports, error when no report exists

Integration tests that assert on verbose log output explicitly set --console=verbose to work correctly under CI auto-detection.

Supersedes

This PR supersedes and unifies the following open issues:

• Redesign Maven console output: smart terminal, log file, structured summaries #11819 — Redesign Maven console output: smart terminal, log file, structured summaries
• [MNG-6662] More concise logging #8571 (MNG-6662) — More concise logging
• [MNG-7484] Collect warnings from different MOJO executions and give a comprehensive summary at the end of the build #8976 (MNG-7484) — Collect warnings from different MOJO executions and give a comprehensive summary at the end of the build
• Change maven cli defaults based on CI env variable #11088 — Change maven CLI defaults based on CI env variable (--console=auto auto-detects CI)
• [MNG-7941] Meaning of -ntp CLI Option vs. --batch-mode #8973 (MNG-7941) — Meaning of -ntp CLI Option vs. --batch-mode (console modes replace this ambiguity)
• [MNG-7372] Maven should display version info in case of error #8043 (MNG-7372) — Maven should display version info in case of error
• [MNG-4639] Be able to profile a maven build #6078 (MNG-4639) — Be able to profile a maven build (build-report.json provides per-mojo timing)

Related:

• [MNG-8071] Build in parallel by default #10872 (MNG-8071) — Build in parallel by default (rich mode provides parallel-aware output, but changing the default to -T is a separate decision)
• [MNG-6899] Maven Runtime Metrics System #8417 (MNG-6899) — Maven Runtime Metrics System (BuildReport captures the core metrics — mojo execution times, module build times; external export to Prometheus etc. is separate work)