kotlinx.ast

kotlinx.ast is a generic AST (Abstract Syntax Tree) parsing library, Kotlin is currently the only supported language. The library is designed that other languages can be easily added. kotlinx.ast does not use the Kotlin Compiler for parsing, it is using ANTLR (the Kotlin variant: https://github.com/Strumenta/antlr-kotlin) using the official Kotlin Grammar (https://kotlinlang.org/docs/reference/grammar.html).

One Component is Klass, a collection of language independent data classes used to represent and easily access the AST.

Status

The Project is in an early stage, but it is already possible to parse Kotlin code. Bug reports, feature requests and pull requests are very welcome.

kotlinx.ast is a multiplatform project, but currently, JVM is the only supported target. Support for JS and native is planned.

antlr-java, antlr-optimized and antlr-kotlin are supported on the JVM. Multiplatform support (Kotlin Native and Kotlin JavaScript) for antlr-kotlin is planned. Because antlr-java and antlr-optimized are JVM-only, support for other platforms is not possible.

Prior art

kastree is using the kotlin compiler for parsing, it can only parse kotlin files. JS and native support is not possible. kastree is currently not under active development.

Example

This Kotlin Code:

@Annotation1("abc")
// line comment between annotations
@Annotation2("\${123}")
fun parse() {}

will be parsed as:

PackageHeader()
importList
KlassDeclaration(fun parse)
  KlassAnnotation(Annotation1)
    KlassArgument()
      KlassString
        "abc"
  KlassAnnotation(Annotation2)
    KlassArgument()
      KlassString
        Escape("\$")
        "{123}"

There are more examples in directory testdata.

• Files named "*.kt.txt" contains the kotlin source to parse
• Files named "*.raw.txt" contains the parsed raw kotlin AST as defined by the official Kotlin Grammar
• Files named "*.summary.txt" contains the AST summary

Open Tasks

There are some parts missing, for example the importList is not converted into an easy-to-use data class

Overview

Currently, there are some libraries that are part of kotlinx.ast:

• kotlinx.ast:common contains the code that can later be reused by other grammar parsers
• kotlinx.ast:common-test contains the dependencies to test frameworks, used by kotlinx.ast unit tests
• kotlinx.ast:parser-antlr-java contains the shared code required to parse grammars using the official antlr4 JVM implementation.
• kotlinx.ast:parser-antlr-kotlin contains the shared code required to parse grammars using antlr-kotlin
• kotlinx.ast:parser-antlr-optimized contains the shared code required to parse grammars using the optimized fork of antlr.
• kotlinx.ast:grammar-kotlin-parser-common contains the shared code required to parse kotlin source
• kotlinx.ast:grammar-kotlin-parser-antlr-java provides a kotlin ast parsed using antlr-java
• kotlinx.ast:grammar-kotlin-parser-antlr-kotlin provides a kotlin ast parsed using antlr-kotlin
• kotlinx.ast:grammar-kotlin-parser-test contains the test data used by the kotlin parsers
• kotlinx.ast:grammar-antlr4-parser-common contains the shared code required to parse antlr4 grammar files
• kotlinx.ast:grammar-antlr4-parser-antlr-java provides an antlr4 grammar ast parser using antlr-java
• kotlinx.ast:grammar-antlr4-parser-test contains the test data used by the antlr4 grammar parsers

External Dependencies

antlr-kotlin

• ${Versions.antlrKotlinGroup}:antlr-kotlin-runtime:${Versions.antlrKotlin} is required at runtime to be able to parse kotlin code into an AST when using kotlinx.ast:grammar-kotlin-parser-antlr-kotlin.

antlr-java

• org.antlr:antlr4:${Versions.antlrJava} is required at runtime to be able to parse kotlin code into an AST when using kotlinx.ast:grammar-kotlin-parser-antlr-java.

antlr-optimized

• com.tunnelvisionlabs:antlr4:${Versions.antlrOptimized} is required at runtime to be able to parse kotlin code into an AST when using kotlinx.ast:grammar-kotlin-parser-antlr-optimized. NOTE: antlr-optimized is a drop-in replacement of antlr-java. Both jars provide the same API, namely the package org.antlr.v4, so you can't use both at the same time. kotlinx.ast:parser-antlr-optimized depends on kotlinx.ast:parser-antlr-java, both provide the same kotlinx.ast API. The difference is that parser-antlr-optimized will exclude the dependency to org.antlr:antlr4 and instead include com.tunnelvisionlabs:antlr4. The generated code of these two libraries is not equal, therefore two different grammar modules are required:
• kotlinx.ast:parser-antlr-java
• kotlinx.ast:parser-antlr-optimized (the generated code is linked, for the case that you want to compare it)

(Versions can be found here: Versions.kt)

How to use kotlinx.ast

There is a small example to get started:

• for antlr-kotlin ExampleMain.kt
• for antlr-java ExampleMain.kt
• for antlr-optimized ExampleMain.kt

Using with Gradle

kotlinx.ast is accessible on Maven & Gradle through Jitpack. In Jitpack basically you can use every commit or tag as a version number. You can find recent versions on the Jitpack page for kotlinx.ast.

You have to add this line to settings.gradle.kts if use Gradle lower than 5.3: (otherwise, the jars are not resolved):

// Enables KotlinMultiplatform publication and resolving (in dependencies)
enableFeaturePreview("GRADLE_METADATA")

You have to add Jitpack to build.gradle.kts:

repositories {
  maven("https://jitpack.io")
}

Add the dependency to kotlinx.ast into your project:

kotlin {
    jvm()

    sourceSets {
        val commonMain by getting {
            dependencies {
                // please look at https://jitpack.io/#drieks/antlr-kotlin to find the latest version
                api("com.github.kotlinx.ast:grammar-kotlin-parser-antlr-kotlin:0123456789")
            }
        }
    }
}

If you don't use kotlin-multiplatform add this line:

// please look at https://jitpack.io/#drieks/antlr-kotlin to find the latest version
implementation("com.github.kotlinx.ast:grammar-kotlin-parser-antlr-kotlin:0123456789")

Or, if you prefer to use the antlr-java parser (JVM only):

// please look at https://jitpack.io/#drieks/antlr-kotlin to find the latest version
implementation("com.github.kotlinx.ast:grammar-kotlin-parser-antlr-java:0123456789")

The latest version can be be seen in the Jitpack-Badge at the top of this page.