Skip parsing generated sources; use compiled classes instead by timtebeek · Pull Request #1142 · openrewrite/rewrite-maven-plugin

timtebeek · 2026-04-11T22:17:22Z

Summary

Generated sources under the build directory (e.g. target/generated-sources/) were being fully parsed into LSTs only to be filtered out afterward
Since getCompileClasspathElements() already includes target/classes with the compiled .class files, type attribution works without parsing the generated sources
Adds filterGeneratedSourceRoots() to exclude source roots under the build directory before scanning, applied consistently in processMainSources(), processTestSources(), and the parsedPaths pre-population
This improves performance for projects that heavily use code generation (protobuf, MapStruct, annotation processors, etc.)
Closes Do not parse generated sources as source files, but only as compiled classes #667

Impact on related issues

Scan the generated sources but not apply change #968 — Requests generated sources be scanned (for search recipes) but not modified. This PR does not regress that use case: generated sources were already fully discarded after parsing, so search results from them were already lost. Properly supporting Scan the generated sources but not apply change #968 would require a GeneratedSource marker, which is orthogonal to this change.
Recipes no longer applied to generated sources after upgrading from 6.26 to 6.27+ #1107 — Recipes no longer applied to generated sources after 6.27+. This PR does not change the filtering behavior introduced in 6.27 (PR Simplify logic surrounding building of Java & Kotlin parsers. #665); it only moves the exclusion earlier (before parsing instead of after). Users who want recipes applied to generated sources need a separate opt-in mechanism.
Incompatibility with Maven Polyglot leads to ParseError #649 — Maven Polyglot ParseError. Unrelated; that issue is about non-standard POM files, not source file handling.

Test plan

Existing unit tests pass (16/16)
Integration test with a project using annotation processing (e.g. MapStruct or Lombok) to verify type attribution still works
Integration test with a protobuf project to verify generated types resolve correctly

…nstead Generated sources under the build directory (e.g. target/generated-sources/) were being fully parsed into LSTs only to be filtered out afterward. Since getCompileClasspathElements() already includes target/classes with the compiled .class files for these sources, type attribution works without parsing them. This adds filterGeneratedSourceRoots() to exclude source roots under the build directory before scanning for source files, avoiding unnecessary parsing work for projects that heavily use code generation (protobuf, MapStruct, annotation processors, etc.). Closes #667

shanman190 · 2026-04-12T01:59:46Z

+        List<String> mainSourceRoots = filterGeneratedSourceRoots(mavenProject, mavenProject.getExecutionProject().getCompileSourceRoots());
+        List<String> testSourceRoots = filterGeneratedSourceRoots(mavenProject, mavenProject.getExecutionProject().getTestCompileSourceRoots());


Won't this result in the files being present in the model as PlainText? Maybe we should -- like the Gradle plugin -- filter out at the end? Avoiding parsing them ahead of time is useful as well though.

You're right, thanks! Changed the approach slightly to still claim the sources through parsedPaths, but not parse them in processMainSources and processTestSources. That should then still achieve the goals set out on #667 for efficiency, without affecting functionality.

Restore unfiltered source roots for parsedPaths pre-population so that OmniParser does not pick up generated .java files as PlainText. The filtering of generated source roots is still applied in processMainSources and processTestSources to skip expensive language parsing, and the buildDirectory filter at the end acts as a safety net.

shanman190

Should we just add this to the isExcluded check on L241? That could probably be converted to a filter like we did in the Gradle plugin.

Move the build directory filter from processMainSources/processTestSources into the unified isExcluded check, matching the Gradle plugin's approach. Generated sources are now excluded in one place alongside user exclusions and gitignore checks, while filterGeneratedSourceRoots still skips expensive language parsing upfront.

…unchanged Move the buildDirectory exclusion out of isExcluded and into the call site at L241 as an inline check, keeping isExcluded's signature and tests unchanged. Remove build directory unit tests that no longer apply to isExcluded directly.

…cludedTest.java

shanman190 · 2026-04-12T16:58:58Z

optional: We could simplify this to a .filter(sourceFile -> !isExcluded(repository, exclusionMatchers, sourceFile.getSourcePath()) && !source.getSourcePath().startsWith(buildDirectory))

moderne-meeseeks Bot added this to OpenRewrite Apr 11, 2026

moderne-meeseeks Bot assigned timtebeek Apr 11, 2026

github-project-automation Bot moved this to In Progress in OpenRewrite Apr 11, 2026

timtebeek moved this from In Progress to Ready to Review in OpenRewrite Apr 11, 2026

timtebeek requested a review from shanman190 April 11, 2026 22:37

shanman190 reviewed Apr 12, 2026

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timtebeek added the enhancement New feature or request label Apr 12, 2026

timtebeek requested a review from shanman190 April 12, 2026 10:37

shanman190 reviewed Apr 12, 2026

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timtebeek added 2 commits April 12, 2026 17:33

shanman190 reviewed Apr 12, 2026

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Comment thread src/test/java/org/openrewrite/maven/MavenMojoProjectParserIsExcludedTest.java Outdated

Update src/test/java/org/openrewrite/maven/MavenMojoProjectParserIsEx…

8ff300b

…cludedTest.java

shanman190 approved these changes Apr 12, 2026

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shanman190 reviewed Apr 12, 2026

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Simplify exclusion to a single .filter() call

02c006d

timtebeek merged commit 1bab148 into main Apr 12, 2026
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timtebeek deleted the tim/generated-sources-classpath branch April 12, 2026 17:30

github-project-automation Bot moved this from Ready to Review to Done in OpenRewrite Apr 12, 2026

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Skip parsing generated sources; use compiled classes instead#1142

Skip parsing generated sources; use compiled classes instead#1142
timtebeek merged 6 commits intomainfrom
tim/generated-sources-classpath

timtebeek commented Apr 11, 2026 •

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		List<String> mainSourceRoots = filterGeneratedSourceRoots(mavenProject, mavenProject.getExecutionProject().getCompileSourceRoots());
		List<String> testSourceRoots = filterGeneratedSourceRoots(mavenProject, mavenProject.getExecutionProject().getTestCompileSourceRoots());

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timtebeek commented Apr 11, 2026 •

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