[perNyfelt]

Summary

Upgrades the build from Groovy 5.1.3 to 6.0.0 and fixes the source incompatibilities Groovy 6 exposed. All source fixes also compile on Groovy 5.1.3.

Breaking for consumers: artifacts compiled with Groovy 6 require a Groovy 6 runtime. Statically compiled call sites bind to new Groovy 6 overloads (e.g. DefaultGroovyMethods.getAt(Map, String)), which throw NoSuchMethodError on Groovy 5. The Matrix static initializer now rejects Groovy < 6 with a clear IllegalStateException; code paths that do not load Matrix (e.g. Stat.frequency(List)) may still fail with NoSuchMethodError on Groovy 5. The published modules' next-release sections note the requirement.

Source fixes

File	Groovy 6 issue	Fix
matrix-core ValueConverter	val is now a keyword; val / x lexed as a slashy string (reported as a misleading "Missing ')'" at line 116)	Renamed variable, use intdiv
matrix-core ValueConverter	default -> try {…} not allowed in switch expressions	Block arm with yield in both branches
matrix-charts MapCoord	Block arm in switch expression must yield	yield 'identity'
matrix-stats Normalize	Unqualified enum case LOG -> rejected at compile time (on Groovy 5 it worked under @CompileStatic, only dynamic code threw MissingPropertyException)	case Normalization.LOG ->
matrix-charts WktReader, matrix-ggplot GgCharmMappingRegistry	default -> null arm infers Object	Cast null to the target type
matrix-gsheets GsUtil, matrix-spreadsheet SpreadsheetUtil	char arithmetic now inferred as Number	Explicit int casts
matrix-gsheets GsUtil	Long/BigInteger ternary no longer typed BigInteger	Explicit cast
matrix-stats Accuracy	def locals mutated in a closure inferred as Number	Declared as BigDecimal
matrix-stats FormulaModelFrameTest	Stricter map literal generics with putAt	Typed locals

Version pins and docs

• gradle/libs.versions.toml: Groovy 6.0.0
• matrix-bom/pom.xml groovy.version 5.1.2 → 6.0.0; BomResolutionIT runtime assertion updated
• matrix-smile/src/test/consumer/build.gradle → 6.0.0
• Groovy versions in module READMEs, root/BOM readmes, docs/tutorial/*, AGENTS.md, matrix-bom/api-coverage.md
• "Targets Groovy 5" statements in readme.md, docs/tutorial/1-introduction.md, docs/tutorial/2-matrix-core.md, docs/cookbook/matrix-core.md, matrix-smile/README.md
• Matrix runtime version check: minimum raised from Groovy 5 to 6
• New "Groovy 6 Pitfalls" section in docs/agents/groovy-style-guide.md
• Release notes: Groovy 6 runtime note in the next-release section of 21 published modules (matrix-logging excluded; matrix-groovy-ext states the requirement without the Matrix-specific failure modes; matrix-bom tells consumers to declare Groovy 6.0.0+) (new "(unreleased)" sections added, using the build.gradle snapshot version, where the top section was already released)

Release tooling

• .github/workflows/release-all-tools.yml: release CLI groovy, groovy-json, groovy-xml 5.1.1 → 6.0.0
• scripts/release-all/staged-settings.groovy: find { … } as Node throws on Groovy 6 (the new XmlExtensions.asType tries to construct a Node), which the catch block reported as a generic "Cannot prepare isolated Maven settings" error. Replaced with (Node) casts; verified on Groovy 5.1.3 and 6.0.0.

Modules touched: matrix-core, matrix-stats, matrix-charts, matrix-ggplot, matrix-gsheets, matrix-spreadsheet, matrix-smile (consumer test), matrix-bom, docs.

Tests

• ./gradlew compileGroovy compileTestGroovy --continue on Groovy 6.0.0: all modules pass

• Same command with v_groovy temporarily set to 5.1.3: all modules pass

• ./gradlew :matrix-core:test :matrix-stats:test :matrix-gsheets:test :matrix-spreadsheet:test :matrix-charts:test :matrix-ggplot:test --continue: all pass (core 680; others 170, 161, 1122, 760, and 1665 with 7 skipped)

• cd matrix-bom && mvn test: MatrixModulesTest 15/15

• cd matrix-bom && mvn verify -Papi-it: all 21 IT classes pass

• After the review fixes: ./gradlew :matrix-core:test 680/680

• ./matrix-bom/preReleaseVerify.sh (Groovy CLI 6.0.0): exit 0. japicmp flags matrix-core changes vs 3.8.0. The only public API changes are Grid.leftShift (def → Grid<T>) and Column.subList(IntRange) (List → Column); both are intentional source changes made on main since 3.8.0, not from this PR. The rest are compiler-generated closure classes.

• Release tooling with Groovy CLI 6.0.0 (same commands as CI): groovy scripts/release-all/test-tools.groovy . (61 assertions), test-inventory-inheritance.groovy ., test-workflow.groovy ., test-manifest-verifier.groovy . .bom-verify-repo: all pass. Before the staged-settings.groovy fix, test-tools and the manifest verifier failed.

Not run: full ./gradlew test for modules without source changes, and shellcheck (no shell scripts changed).

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