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pigweed/third_party/github/JetBrains/kotlin/refs/heads/upstream/ic/direct-java-4-dev/./compiler/java-direct
tree: 2a9d464388e678f3c23d00c392a22726e4d16897 [search]
  1. implDocs/
  2. src/
  3. test/
  4. testFixtures/
  5. AGENT_INSTRUCTIONS.md
  6. AGENT_INSTRUCTIONS_COMMON.md
  7. build.gradle.kts
  8. ITERATION_RESULTS.md
  9. ReadMe.md
compiler/java-direct/ReadMe.md

Java Facade for Kotlin compiler

A lightweight “direct” implementation of the compiler's Java model, replacing the PSI-based facade that pulls a lot of IntelliJ platform code into the compiler. Enabled by the -Xjava-direct compiler option, which switches both the Java source and the binary class paths to this module.

Purpose

Kotlin has bidirectional Java interop: a module can contain Java files referencing Kotlin declarations and vice versa, so the compiler cannot rely on Java files being available in binary form and must process Java sources directly, exposing their declarations to FIR resolution. This was originally implemented via IntelliJ platform infrastructure (the PSI-based Java facade); this module provides the same JavaClassFinder / org.jetbrains.kotlin.load.java.structure model without it.

Architecture

  • Parser: the lightweight KMP Java parser (org.jetbrains:syntax-api, org.jetbrains:java-syntax, published by the Fleet team), producing a light-tree structure with no IntelliJ platform dependencies.
  • Laziness: source roots are scanned lazily — directory roots are descended only when a package is requested; files are pre-scanned (lexer-only) for package/top-level names and parsed only when FIR asks for a class. Model extraction on top of the parsed tree is also lazy and cached.
  • Java model: JavaClassFinderOverAstImpl (sources) and JavaClassFinderOverBinaryIndex (binaries) return model entities from org.jetbrains.kotlin.java.direct.model.
  • Resolution: unlike the PSI facade, all non-Java-source references (binary classes, Kotlin declarations) are resolved through FIR via the FirSession, and the results are wrapped back into the Java model (FirBackedJava* classes).

Detailed maps live in implDocs/:

  • implDocs/ARCHITECTURE.md — key files, callback patterns, JLS implicit rules.
  • implDocs/RESOLUTION_PIPELINE.md and implDocs/RESOLUTION_SCHEMA.md — the resolution entities and the end-to-end scenarios (classifier lookup, JLS 6.4/6.5 name resolution, inherited member types, implicit outer type arguments, annotations, constants).
  • implDocs/PSI_FREE_ROADMAP.md — the PSI-free / platform-free status and remaining work.

Tests

The module contains unit tests (JavaParsing*) and also “steals” all phased diagnostics and box tests that contain Java files from the main compiler test data (JavaUsingAstPhasedTestGenerated, JavaUsingAstBoxTestGenerated), plus a java-direct-owned testData/diagnostics root for javac-conformant behaviour that deliberately differs from the PSI model.