Kotlin: support 2.4.20-RC3 by andersfugmann · Pull Request #22404 · github/codeql

andersfugmann · 2026-08-21T11:44:17Z

Summary

Support Kotlin 2.4.20-RC2 in the Kotlin extractor. Kotlin 2.4.20 GA remains unsupported.

The implementation is split between release-driven compatibility changes and two observed RC2 behaviours. The release changelog explicitly removes remaining ComponentRegistrar usage (KT-85816) and applies @K1Deprecation to public K1 APIs (KT-86046). The RC2 compiler also gives generated interface forwarders synthetic source offsets and rejects the previous repeatable-annotation access path. The extractor adapts to those behaviours without changing query results.

Motivation for each change

Change	Motivation
Add standalone, embeddable, and standard-library RC2 artefacts	Build and test the extractor against the published `v2.4.20-RC2` compiler rather than an inferred compatible version.
Add an 2.4.20-specific `CompilerPluginRegistrar` implementation	`ComponentRegistrar` is absent from the 2.4.20 compiler, matching KT-85816. The existing registrar cannot be loaded because it implements both APIs.
Package the legacy `ComponentRegistrar` service only before 2.4.20	Older compilers still require the legacy service, while 2.4.20 fails if that service refers to the removed class. This keeps compatibility selection at the build boundary.
Opt in to `org.jetbrains.kotlin.K1Deprecation` from 2.4.20	The extractor still uses K1 compatibility APIs. KT-86046 makes the opt-in an error-level requirement in 2.4.20.
Reuse the `annotationClass` compatibility extension	2.4.20 rejects the previous IR parent access. The existing extension uses `constructedClass` and also compiles with the oldest supported Kotlin 1.8.0 compiler.
Assign fabricated interface forwarders the enclosing class location	2.4.20 reports synthetic offsets for these generated declarations. They have no direct source declaration, so the enclosing class is the stable location and preserves previous database and query output. This behaviour was observed during extraction and is not called out explicitly in the release changelog.
Make 2.4.20-RC2 the development and Kotlin 2 test default	Exercise the newly supported compiler in the normal Kotlin 2 suite.
Test 2.4.20 GA in the too-new diagnostic	Verify the intended RC2-only boundary directly.
Update documentation and the change note to 2.4.20-RC2	Avoid implying support for 2.4.20 GA.

Compatibility

Compiler variants before 2.4.20 retain their existing registrar and service packaging.
The K1 opt-in changes compilation only and does not change extracted data.
Repeatable annotation extraction uses the existing cross-version compatibility path.
Generated forwarders retain their previous observable locations. No fake-override, AST, expression-type, or inherited-interface-default expectations change.
Kotlin 2.4.20 GA and other prerelease spellings remain unsupported.

Validation

Built all 26 extractor variants: standalone and embeddable for every compiler version declared in VERSIONS
Ran ten representative tests for every supported compiler and applicable language mode: K1 for Kotlin 1.8 through 2.3, and K2 for Kotlin 2.0 through 2.4
Built standalone and embeddable 2.4.20-RC2 extractor variants
Built the oldest supported 1.8.0 extractor variant
Full Kotlin 2 suite passed in eight sequential shards with one test thread
Full Kotlin 1 suite passed with 2.3.20 in eight sequential shards with one test thread
All 36 Kotlin all-platform extraction tests passed in eight sequential shards
All 63 Kotlin all-platform QL integration tests passed in eight sequential shards
The published v2.4.20-RC2 compiler passed the Kotlin basic functionality extraction test
The too-new diagnostic test rejects 2.4.20 GA

No tests are disabled. The only changed generated expectation is the too-new diagnostic.

andersfugmann · 2026-08-28T11:41:57Z

Bumped artifacts to Kotlin 2.4.20-RC2

Copilot

Copilot review overview

Review tier: Balanced
Findings: None

What changed in this PR

Adds preliminary Kotlin 2.4.20-RC2 extractor support while continuing to reject Kotlin 2.4.20 GA.

Changes:

Adds RC2 compiler dependencies and extractor variants.
Adapts compiler registration, annotations, and synthetic forwarder locations.
Updates defaults, diagnostics, documentation, and release notes.

File	Description
`MODULE.bazel`	Registers RC2 dependency repositories.
`java/ql/lib/change-notes/2026-08-21-kotlin-2.4.20.md`	Announces preliminary support.
`java/ql/integration-tests/kotlin/all-platforms/diagnostics/kotlin-version-too-new/fake-kotlinc-source/kotlin/KotlinVersion.java`	Tests the GA rejection boundary.
`java/ql/integration-tests/kotlin/all-platforms/diagnostics/kotlin-version-too-new/diagnostics.expected`	Updates the expected diagnostic.
`java/kotlin-extractor/versions.bzl`	Adds the RC2 extractor version.
`java/kotlin-extractor/src/main/kotlin/utils/versions/v_2_4_20-RC2/Kotlin2ComponentRegistrar.kt`	Implements the supported registrar API.
`java/kotlin-extractor/src/main/kotlin/MetaAnnotationSupport.kt`	Uses compatible annotation-class access.
`java/kotlin-extractor/src/main/kotlin/KotlinFileExtractor.kt`	Stabilizes generated forwarder locations.
`java/kotlin-extractor/dev/wrapper.py`	Makes RC2 the development default.
`java/kotlin-extractor/deps/kotlin-stdlib-2.4.20-RC2.jar`	Adds the RC2 standard library artifact.
`java/kotlin-extractor/deps/kotlin-compiler-embeddable-2.4.20-RC2.jar`	Adds the embeddable compiler artifact.
`java/kotlin-extractor/deps/kotlin-compiler-2.4.20-RC2.jar`	Adds the standalone compiler artifact.
`java/kotlin-extractor/BUILD.bazel`	Configures version-specific APIs and services.
`docs/codeql/reusables/supported-versions-compilers.rst`	Documents preliminary RC2 support.

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jketema

First round of comments. There is an RC3 btw.

andersfugmann · 2026-09-03T12:07:40Z

First round of comments. There is an RC3 btw.

I will address the other comments first and then push an update to move support to RC3.

jketema

One remaining question, otherwise this LGTM.

jketema · 2026-09-03T14:53:21Z

            metaAnnotations.find {
-                it.symbol.owner.parentAsClass.fqNameWhenAvailable ==
-                    JvmAnnotationNames.REPEATABLE_ANNOTATION
+                it.annotationClass.fqNameWhenAvailable == JvmAnnotationNames.REPEATABLE_ANNOTATION


Why does this work with earlier Kotlin versions?

annotationClass resolves the class though symbol.owner.constructedClass, which is available for all Kotlin versions, and is already (prior to this PR) used in groupRepeatableAnnotations.

symbol.owner.constructedClass and parentAsClass are for an IrConstructor semantically equivalent. constructor.constructedClass is implemented as constructor.parent as IrClass. parentAsClass also reads parent and requires it to be an IrClass. The only difference is the exception produces if its not an IrClass

Copilot has scanned all the supported versions (>= 1.8.0) to verify that its supported:

I checked every compiler variant supported by this extractor, from Kotlin 1.8.0 through 2.4.20-RC3. constructedClass has the same implementation in all of them. This is safe for our supported versions because an IrConstructor is expected to be parented by the class it constructs

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin 2.4.20-RC removes the remaining ComponentRegistrar API under KT-85816. Use an RC-specific registrar that only implements CompilerPluginRegistrar, and package the legacy ComponentRegistrar service only for older compilers. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin 2.4.20-RC marks public K1 APIs with K1Deprecation under KT-86046 and rejects the previous repeatable-annotation IR access path. Opt in to K1Deprecation for 2.4.20 and later, and use the existing annotationClass compatibility extension. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin 2.4.20-RC assigns synthetic source offsets to generated interface forwarders. Use the enclosing class location for each fabricated forwarder and its generated body and accesses, preserving existing database and query output. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Replace the previous 2.4.20-RC dependency set and compatibility marker with RC2 while preserving existing extraction output. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

jketema

Approving the current version. I assume this will still need to be rebase/updated a few times, but let's hope the extractor fixes will be stable.

github-actions Bot added documentation Java Kotlin labels Aug 21, 2026

andersfugmann force-pushed the andersfugmann/kotlin-2.4.20rc branch 8 times, most recently from 2fa6f32 to b9c81d5 Compare August 26, 2026 11:25

andersfugmann removed the Java label Aug 26, 2026

andersfugmann self-assigned this Aug 26, 2026

github-actions Bot added the Java label Aug 26, 2026

andersfugmann changed the title ~~Kotlin: support 2.4.20-RC~~ Kotlin: support 2.4.20-RC2 Aug 28, 2026

andersfugmann marked this pull request as ready for review August 28, 2026 11:42

Copilot AI balanced review requested due to automatic review settings August 28, 2026 11:42

andersfugmann requested review from a team as code owners August 28, 2026 11:42

Copilot started reviewing on behalf of andersfugmann August 28, 2026 11:43 View session

Copilot AI reviewed Aug 28, 2026

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andersfugmann mentioned this pull request Aug 28, 2026

Kotlin: cover 2.4.20 language features #22462

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jketema reviewed Sep 2, 2026

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andersfugmann force-pushed the andersfugmann/kotlin-2.4.20rc branch from a07ec7b to 00bb879 Compare September 3, 2026 14:41

andersfugmann changed the title ~~Kotlin: support 2.4.20-RC2~~ Kotlin: support 2.4.20-RC3 Sep 3, 2026

jketema reviewed Sep 3, 2026

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andersfugmann and others added 11 commits September 4, 2026 10:24

Kotlin: add 2.4.20-RC artifacts

b6f5682

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: enable 2.4.20-RC support

6e54904

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: make 2.4.20-RC the test default

77bc0b6

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: document preliminary 2.4.20-RC support

da6394d

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: support 2.4.20-RC2

d05ce39

Replace the previous 2.4.20-RC dependency set and compatibility marker with RC2 while preserving existing extraction output. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: document preliminary 2.4.20 support

0534c6c

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: restore future-version diagnostic test

5e9dec1

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Kotlin: support 2.4.20-RC3

e7e97c4

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

andersfugmann force-pushed the andersfugmann/kotlin-2.4.20rc branch from 00bb879 to e7e97c4 Compare September 4, 2026 08:24

jketema approved these changes Sep 4, 2026

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Kotlin: support 2.4.20-RC3 - #22404

Kotlin: support 2.4.20-RC3#22404
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andersfugmann commented Aug 21, 2026 •

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Summary

Motivation for each change

Compatibility

Validation

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andersfugmann commented Aug 21, 2026 •

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andersfugmann commented Sep 3, 2026 •

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