refactor: migrate all Xtend files to Java 21 by joaodinissf · Pull Request #1274 · dsldevkit/dsl-devkit

joaodinissf · 2026-03-01T08:34:53Z

Summary

Migrate all 88 Xtend (.xtend) source files to Java 21, leveraging modern language features (text blocks, enhanced switch, pattern matching, records). This eliminates the Xtend compilation step, significantly improving build times.

What's included

Xtend-to-Java migration of all .xtend files across check, checkcfg, export, expression, format, scope, and generator modules (Batches 1–9)
Xtend build infrastructure removal (maven-xtend-plugin, xtend-maven-plugin configs)
Code quality fixes: resolve all PMD, Checkstyle, and SpotBugs violations in migrated code
Modern Java idioms: replace StringBuilder patterns with String.format() and text blocks, convert string concatenation to text blocks in test DSL sources
Eclipse formatter applied to all migrated files
@SuppressWarnings("nls") added to suppress non-externalized string literal warnings

Build impact

Clean Eclipse build ~2.8x faster: from 14.44s down to 5.13s (measured on MacBook).

Test plan

CI maven-verify passes
CI PMD and Checkstyle checks pass
Manual verification in Eclipse IDE

🤖 Generated with Claude Code

rubenporras · 2026-03-02T09:39:16Z

+   * @return the model stub string
+   */
+  public String modelWithGrammar() {
+    StringBuilder builder = new StringBuilder(512);


@joaodinissf it is not using multi line strings...

Good catch, I'll try to get it to clean this up later today.

rubenporras · 2026-04-16T12:46:35Z

-       *
-       * Also see {@link org.eclipse.xtext.xtext.XtextFormatter} as an example
-       */
-      public class «grammar.formatterStub.simpleName» extends «FormatGeneratorUtil::getFormatterName(grammar, "Abstract")» {


I think that for this kind of files were use use Xtend string interpolation, it actually makes sense to keep Xtend.

@accessors

Convert all 8 Xtend source files in com.avaloq.tools.ddk.check.core to plain Java 21, eliminating the org.eclipse.xtend2.lib dependency: - CheckGeneratorConfig: @accessors → manual getter/setter - CheckTypeComputer: override → @OverRide, typeof → .class - CheckGeneratorNaming: static utilities, explicit types - CheckScopeProvider: dispatch methods → if-instanceof dispatcher - CheckGeneratorExtensions: 4 dispatch families, switch expressions - CheckFormatter: dispatch _format methods, extension→explicit calls - CheckGenerator: template expressions → StringBuilder (no StringConcatenation) - CheckJvmModelInferrer: extension fields, JvmTypesBuilder lambdas Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Xtend doesn't enforce checked exceptions, but Java does. Moved file.getContents() call inside try-with-resources block to properly handle CoreException. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Migrate 28 Xtend files across 14 modules to idiomatic Java 21. All files are Trivial/Easy complexity (≤100 lines each). Modules touched: check.core.test, check.test.runtime, check.test.runtime.tests, check.ui, checkcfg.core, checkcfg.core.test, sample.helloworld.ui.test, xtext.check.generator, xtext.expression, xtext.format, xtext.format.ide, xtext.format.test, xtext.format.ui, xtext.generator Progress: 36/94 files migrated (38%) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Migrate 13 Xtend files across 8 modules: - check.core.test: CheckApiAccessValidationsTest, ProjectBasedTests, IssueCodeValueTest, BasicModelTest - check.test.runtime.tests: CheckExecutionEnvironmentProjectTest - sample.helloworld.ui.test: CheckExecutionEnvironmentProjectTest - checkcfg.core: PropertiesInferenceHelper - checkcfg.core.test: CheckCfgScopeProviderTest, CheckCfgContentAssistTest, CheckCfgSyntaxTest - xtext.export.generator: ExportFragment2 - xtext.scope.generator: ScopingFragment2 - xtext.test.core: Tag Progress: 49/94 files migrated (52%). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

@Inject

Migrate all 9 remaining Xtend files in the xtext.export module to idiomatic Java 21, completing the module. Includes template expressions converted to StringBuilder, dispatch methods with Java 21 pattern matching, and @Inject extension rewrites. Files: ResourceDescriptionConstantsGenerator, ExportFeatureExtensionGenerator, ResourceDescriptionManagerGenerator, ExportedNamesProviderGenerator, FragmentProviderGenerator, ExportGenerator, FingerprintComputerGenerator, ExportGeneratorX, ResourceDescriptionStrategyGenerator. Progress: 58/94 files migrated (62%). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Migrate 10 Xtend files across 5 modules: xtext.expression (3), xtext.scope (4), xtext.test.core (1), xtext.ui (1), xtext.ui.test (1). Heavy use of dispatch methods (ExpressionExtensionsX, GenModelUtilX, CodeGenerationX, ScopeNameProviderGenerator, ScopeProviderX, ScopeProviderGenerator) converted to Java 21 pattern matching dispatchers. Template expressions converted to StringBuilder. Modules fully migrated: xtext.expression, xtext.scope, xtext.test.core, xtext.ui, xtext.ui.test. Progress: 68/94 files migrated (72%). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…mplete! All 94 Xtend source files have been migrated to Java 21. Zero .xtend files remain in src/ directories. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Remove all xtend-gen references from .classpath, build.properties, pom.xml (xtend-maven-plugin, xtend.version property, PMD exclude, clean plugin fileset), PMD ruleset, Checkstyle config, and .gitignore. Remove org.eclipse.xtend.lib from MANIFEST.MF where no longer needed (kept in xtext.generator, check.core.test, sample.helloworld.ui, and xtext.test.core which still use xtend2.lib runtime classes or xtend.lib annotations). Remove migration section from AGENTS.md. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Fix ~396 violations across 12 files in 5 modules (xtext.expression, xtext.format, xtext.ui, xtext.ui.test, xtext.check.generator): - Suppress dispatch method naming and unused params at class level - Rename underscore-prefixed fields and lambda parameters - Use char literals in StringBuilder.append for single characters - Add StringBuilder capacity, extract string constants, fix Javadoc - Simplify boolean returns, fix loose coupling, remove unnecessary boxing - Extract long lambdas into private methods, fix varargs array creation Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

@OverRide

- Remove superfluous instanceof check in CodeGenerationX - Simplify inferConstants boolean return in FormatJvmModelInferrer - Add @OverRide on infer() dispatch method - Cast null to Object[] to clarify varargs intent in test Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…nd export modules Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Resolve ~600 PMD and Checkstyle violations across all modules affected by the Xtend-to-Java migration: check.core, check.core.test, check.ui, check.ui.test, checkcfg.core, checkcfg.core.test, format.generator, export.generator, generator.test, and generator. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

… MissingOverride, LooseCoupling) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…t blocks Replace StringBuilder.append() chains with more readable alternatives: - Text blocks with String.format() for file skeleton generators (CheckNewProject, CheckQuickfixProvider, CheckProjectFactory, ExportGenerator) - String.format() for toString() methods in scope classes and resource descriptions - Simple string concatenation for trivial cases (EObjectUtil, AbstractLabelProvider, ClasspathBasedChecks, DirectLinkingResourceStorageLoadable) - String.join() for loop-based string building (ScopeTrace) Also widens toClient() parameter from StringBuilder to CharSequence in StandaloneBuilderIntegrationFragment2 and LspBuilderIntegrationFragment2, and removes unused INITIAL_BUFFER_CAPACITY constants. 18 files changed, net -106 lines removed. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…rces Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

… simple concatenation Replace StringBuilder.append() chains with Java 21 text blocks, String.format(), and simple concatenation across 11 files where the pattern was a mechanical artifact of the Xtend-to-Java migration. Remaining StringBuilder instances (74 across 20 files) are intentionally kept where loops, interleaved conditionals, or dispatch group consistency make them the better choice. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Fixes PMD UseTryWithResources violation introduced during Xtend-to-Java migration, now that upstream enabled this rule. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

@SuppressWarnings

Xtend didn't enforce NLS externalization. Adding @SuppressWarnings("nls") at class level for all 76 migrated files to silence Eclipse warnings. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Fixes PMD UseTryWithResources violation for ByteArrayInputStream. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Plan for landing the completed migration on master in 12 reviewable weekly slices, cut leaves-to-trunk by plugin family, with a shared per-file review checklist. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Add a structured project skill encoding the Xtend → Java conversion rules and methodology that previously lived only in the stale PR dsldevkit#1274 (`docs/xtend-to-java-conversion-prompt.md` and `docs/xtend-migration.md`). The skill is split into a 1-line entry point, 10 rule files, 4 workflow docs, 2 examples, and 1 reference table — Claude (or any LLM) can load only the parts it needs. Cross-tool generic location at `.agents/skills/` is the source of truth. A POSIX shell script `.agents/sync.sh` mirrors it into `.claude/skills/` (gitignored) for Claude Code's auto-discovery: symlink on macOS/Linux, recursive copy on Windows where Git symlinks need Developer Mode. After cloning, run `./.agents/sync.sh` once. Re-run after pulling changes that touch `.agents/skills/`. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

joaodinissf changed the title ~~[CLAUDE] Xtend to Java migration~~ [WIP] Xtend to Java migration Mar 1, 2026

rubenporras reviewed Mar 2, 2026

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joaodinissf marked this pull request as ready for review March 3, 2026 08:24

joaodinissf changed the title ~~[WIP] Xtend to Java migration~~ refactor: migrate all Xtend files to Java 21 Mar 3, 2026

joaodinissf force-pushed the feature/xtend-to-java-migration branch 3 times, most recently from 84de93f to 76087e2 Compare March 3, 2026 18:38

joaodinissf marked this pull request as draft March 5, 2026 08:41

joaodinissf force-pushed the feature/xtend-to-java-migration branch 2 times, most recently from dee50e3 to 4163b68 Compare April 4, 2026 11:55

rubenporras reviewed Apr 16, 2026

View reviewed changes

joaodinissf force-pushed the feature/xtend-to-java-migration branch from 77c62fd to 169f93c Compare April 17, 2026 23:11

joaodinissf and others added 18 commits April 20, 2026 10:22

fix: handle checked CoreException in CheckGeneratorExtensions

008a92a

Xtend doesn't enforce checked exceptions, but Java does. Moved file.getContents() call inside try-with-resources block to properly handle CoreException. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

chore: add migration docs and update project files

57c7cbb

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

feat: migrate Batch 7 Xtend files to Java 21 (6 files)

360c6eb

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

feat: migrate Batch 8 Xtend files to Java 21 (17 files)

8ebe1ec

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

feat: migrate Batch 9 Xtend files to Java 21 (5 files) — migration co…

7ff519f

…mplete! All 94 Xtend source files have been migrated to Java 21. Zero .xtend files remain in src/ directories. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

style: resolve all PMD and checkstyle warnings in generator, scope, a…

47c266d

…nd export modules Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

style: fix UnnecessaryBoxing in AnnotationAwareAntlrGrammarGenerator

94d45c5

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

style: fix remaining PMD violations (StringToString, UnnecessaryCast,…

8b2d6cb

… MissingOverride, LooseCoupling) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

style: fix UseCollectionIsEmpty in PropertiesInferenceHelper

ea767d8

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

joaodinissf and others added 9 commits April 20, 2026 10:22

fix: resolve BasicEList compilation error in XbaseGeneratorFragmentTest

b88ab42

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs: add handover summary for Xtend-to-Java migration session

ab99b1a

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

refactor: convert string concatenation to text blocks in test DSL sou…

34ea17f

…rces Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fix: use try-with-resources in ProjectBasedTests.isEmpty()

9974245

Fixes PMD UseTryWithResources violation introduced during Xtend-to-Java migration, now that upstream enabled this rule. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

style: suppress NLS warnings on migrated Xtend-to-Java classes

01ac135

Xtend didn't enforce NLS externalization. Adding @SuppressWarnings("nls") at class level for all 76 migrated files to silence Eclipse warnings. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fix: use try-with-resources in IssueCodeValueTest

542aaf6

Fixes PMD UseTryWithResources violation for ByteArrayInputStream. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs: add Xtend-to-Java migration roadmap

5710dd2

Plan for landing the completed migration on master in 12 reviewable weekly slices, cut leaves-to-trunk by plugin family, with a shared per-file review checklist. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

joaodinissf force-pushed the feature/xtend-to-java-migration branch from fddb296 to 5710dd2 Compare April 20, 2026 08:22

joaodinissf mentioned this pull request May 19, 2026

build: add Xtend → Java migration skill at .agents/skills/ #1351

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refactor: migrate all Xtend files to Java 21#1274

refactor: migrate all Xtend files to Java 21#1274
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joaodinissf commented Mar 1, 2026 •

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Summary

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rubenporras Mar 2, 2026

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joaodinissf commented Mar 1, 2026 •

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