Use K2Compiler via JvmFirPipeline to support Kotlin v2 by Crustack · Pull Request #6338 · openrewrite/rewrite

Crustack · 2025-11-25T12:53:45Z

What's changed?

Update kotlin-compiler dependencies to 2.2.21
Implement JvmFirPipeline to use current K2 phased compiler API (with disabled fail on compile errors) to generate FirFiles
Update KotlinIrTypeMapping, IrTreeVisitor, KotlinTypeIrSignatureBuilder to be compilable, but they are not used atm
Update KotlinTypeMapping, KotlinTypeSignatureBuilder, PsiElementAssociations for new compiler dependency versions to be compilable
Check all rewrite-kotlin and rewrite-gradle tests still work and adjust KotlinTypeMapping, KotlinTypeSignatureBuilder, PsiElementAssociations if necessary
For synthetic source files the contents are pasted into a temp folder to provide compiler with actual file path

What's your motivation?

Closes Support for Kotlin 2.2.0 Projects #6007
Groundwork for WIP: Use IR for KotlinParser instead of PSI/FIR #6325 to implement proper kotlin gradle support

Anyone you would like to review specifically?

@shanman190
@jkschneider

Checklist

I've added unit tests to cover both positive and negative cases
I've read and applied the recipe conventions and best practices
I've used the IntelliJ IDEA auto-formatter on affected files

rewrite-kotlin/src/main/java/org/openrewrite/kotlin/KotlinParser.java

Crustack · 2025-12-13T12:07:26Z

@timtebeek @shanman190 @jkschneider PR is now ready for proper review

FYI: I also tested adding support for properly compiling build.gradle.kts with Kotlin DSL, which works great and enables proper Kotlin support for many gradle recipes.
I will add another PR for it if/after this has been merged

timtebeek

Thanks for your continued efforts here @Crustack ! For the uninitiated (me) could you explain a bit about the what the FIR processing is / adds, and any trade offs as compared to what we had before, and impact on say Kotlin v1 support? That would mean we're better able to review this work, as it seems promising but it's a bit hard to say without more context.

timtebeek · 2025-12-15T18:39:54Z

rewrite-kotlin/src/main/java/org/openrewrite/kotlin/KotlinParser.java

+    // TODO: Compiler Source File args need to be an actual file path therefore copying synthetic file to temp folder
+    public static String tempFile(ExecutionContext ctx, Input source, AtomicInteger idx) {
+        String fileName;
+        if ("openRewriteFile.kt".equals(source.getPath().toString())) {
+            fileName = "openRewriteFile" + idx.getAndIncrement() + ".kt";
+        } else if ("openRewriteFile.kts".equals(source.getPath().toString())) {
+            fileName = "openRewriteFile" + idx.getAndIncrement() + ".kts";
+        } else {
+            fileName = source.getPath().toString();
+        }
+        if(TEMP_SOURCE_DIR == null) {
+            try {
+                TEMP_SOURCE_DIR = Files.createTempDirectory("rewrite");
+            } catch (IOException e) {
+                throw new RuntimeException(e);
            }
        }
-        addJvmClasspathRoot(compilerConfiguration, PathUtil.getResourcePathForClass(AnnotationTarget.class));
+        Path tempFile = TEMP_SOURCE_DIR.resolve(fileName);
+        try {
+            Files.createDirectories(tempFile.getParent());
+            Files.copy(source.getSource(ctx), tempFile, StandardCopyOption.REPLACE_EXISTING);
+        } catch (FileAlreadyExistsException ignored) {
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+        return tempFile.toAbsolutePath().toString();
+    }


Calling this out for my colleagues as creating files on disk might be a little different when it concerns the CLI / workers.

I was trying to use the WorkingDirectoryExecutionContextView's working directory to create these temp files (which is only necessary for synthetic temp files in Unit Tests), but executing:

WorkingDirectoryExecutionContextView.view(ctx).getWorkingDirectory()

In Unit Tests throws NullPointerException, because the context has no CURRENT_CYCLE` message. Not sure how to proceed on this.

timtebeek · 2025-12-15T18:41:02Z

rewrite-kotlin/src/main/kotlin/org/openrewrite/kotlin/KotlinIrTypeMapping.kt

+            is IrSimpleType -> {
+                when (type.getPrimitiveType()) {
+                    PrimitiveType.INT -> JavaType.Primitive.Int
+                    PrimitiveType.BOOLEAN -> JavaType.Primitive.Boolean
+                    PrimitiveType.BYTE -> JavaType.Primitive.Byte
+                    PrimitiveType.CHAR -> JavaType.Primitive.Char
+                    PrimitiveType.DOUBLE -> JavaType.Primitive.Double
+                    PrimitiveType.FLOAT -> JavaType.Primitive.Float
+                    PrimitiveType.LONG -> JavaType.Primitive.Long
+                    PrimitiveType.SHORT -> JavaType.Primitive.Short
+                    else -> when {
+                        type.isStringClassType() -> JavaType.Primitive.String
+                        type.isNothing() || type.isNullableNothing() -> JavaType.Primitive.None
+                        else -> JavaType.Primitive.None


Love that you've thought to do this as well; it's been a bit of a sore point to me that some Spring migration method patterns failed to match because they were using Java primitives instead of Kotlin primitives.

timtebeek · 2026-01-14T09:50:23Z

Thanks for your continued efforts here @Crustack ! For the uninitiated (me) could you explain a bit about the what the FIR processing is / adds, and any trade offs as compared to what we had before, and impact on say Kotlin v1 support? That would mean we're better able to review this work, as it seems promising but it's a bit hard to say without more context.

Not sure if you'd seen my earlier comment @Crustack , but it would help us better judge the scope & impact of the work done here, and how it compares to our support for Kotlin v1. Is v1 still supported with your changes for instance?

Crustack · 2026-01-18T12:53:48Z

Not sure if you'd seen my earlier comment @Crustack , but it would help us better judge the scope & impact of the work done here, and how it compares to our support for Kotlin v1. Is v1 still supported with your changes for instance?

Hi @timtebeek , sorry for not responding earlier.
With the changes of this PR:

KotlinParser still uses PSI+FIR as before, but just with the newer Kotlin Compiler API
Uses the new K2 Compiler and supports Kotlin v2 (which was already attempted by Kotlin 2 #5963, Add support for Kotlin 2.x #5575)
All Kotlin Tests also pass for e.g. Kotlin v1.9
I also figured out how to utilize gradle Kotlin Script Templates with the new compiler API to better parse build.gradle.kts files and improve method/field matching for them (which I can submit in a future PR)
In a next step you could improve Kotlin parsing further by compiling to IR by adding the JvmFir2IrPipelinePhase to JvmFirPipeline (see JvmCliPipeline)

timtebeek · 2026-02-18T23:09:28Z

Thanks again for your help here @Crustack ! Youl'll find some of the same changes you've suggested merged in this PR

Upgrade rewrite-kotlin to Kotlin 2 compiler (K2) #6766

Hope that has you going with 2.2 support for your use cases there!

Crustack · 2026-02-19T16:43:23Z

To be honest I'm a bit disappointed that over the course of 3 months this PR has not been actually reviewed and then to see an internal PR being created separately and merged immediately.
I would have gladly provided more info or respond to any given feedback.
I understand that internal contributions are generally preferred over outsiders', but since this took a lot of effort, I feel like I could have worked on something else instead if I knew there was no actual interest in it.
But, I will also admit that I should have probably reached out sooner on Slack, I just thought since there was no activity in #5963 and #5575 that it would be welcomed...

Thanks to @timtebeek for the initial feedback, and I'm glad to see K2 support being added

Have a nice week.

timtebeek · 2026-02-20T09:50:51Z

Hi @Crustack ; understandable that you're disappointed to not see this explicitly evaluated in depth or merge;d know that it's never easy to decide which of competing PRs to continue from, as we had in this case. You might have noticed that in this case Marius' original work in #5575 was reflected in the commits. Know that your explorations did help validate the work done in the PR we merged, and was appreciated.

With larger efforts like these it's often hard to get alignment among all involved, and different folks have different styles of working through changes. Pulling work from different branches can than complicate matters when we're looking to get this delivered, but know that it's not our standard way of working.

Should you have any subsequent work you're considering do please reach out, via Slack or here, and I'll do my best to see things through where I can. In this case I myself wasn't confident enough to continue your work, as also evidenced by my earlier comments. But not that support for v2 is here, it should be easier to extend should you find room for improvement. 🙏🏻

timtebeek · 2026-02-22T21:54:17Z

@Crustack based on your hints above I figured explore Kotlin script templates for .kts; figured you'd be interested

Thanks again!

github-project-automation bot added this to OpenRewrite Nov 25, 2025

github-project-automation bot moved this to In Progress in OpenRewrite Nov 25, 2025

moderne-meeseeks bot assigned Crustack Nov 25, 2025

Crustack mentioned this pull request Nov 25, 2025

WIP: Use IR for KotlinParser instead of PSI/FIR #6325

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Crustack marked this pull request as draft November 25, 2025 12:54

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rewrite-kotlin/src/main/java/org/openrewrite/kotlin/KotlinParser.java Outdated Show resolved Hide resolved

timtebeek added kotlin parser labels Nov 25, 2025

Use K2Compiler via JvmFirPipeline to support Kotlin v2

7abd4c2

Crustack force-pushed the feat/kotlin-v2 branch from 26310be to 7abd4c2 Compare December 13, 2025 12:05

Crustack marked this pull request as ready for review December 13, 2025 12:06

timtebeek reviewed Dec 15, 2025

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timtebeek mentioned this pull request Dec 22, 2025

Support Kotlin String in MigrateUserToContext openrewrite/rewrite-feature-flags#59

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Merge branch 'main' into feat/kotlin-v2

bc429e3

flex-gwanbin mentioned this pull request Jan 28, 2026

When Kotlin 2.x is supported? #6621

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timtebeek mentioned this pull request Feb 18, 2026

Upgrade rewrite-kotlin to Kotlin 2 compiler (K2) #6766

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github-project-automation bot moved this from In Progress to Done in OpenRewrite Feb 18, 2026

Crustack deleted the feat/kotlin-v2 branch February 19, 2026 16:43

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Use K2Compiler via JvmFirPipeline to support Kotlin v2#6338

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