Use K2Compiler via JvmFirPipeline to support Kotlin v2 #6338

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)

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

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Use K2Compiler via JvmFirPipeline to support Kotlin v2 #6338

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