antlr4ts - TypeScript/JavaScript target for ANTLR 4
Overview
- Releases: See the GitHub Releases page for release notes and
links to the distribution
- Feedback: Use GitHub Issues for issues (bugs, enhancements,
features, and questions)
Requirements
This project has separate requirements for developers and end users.
:bulb: The requirements listed on this page only cover user scenarios - that is, scenarios where developers wish to
use ANTLR 4 for parsing tasks inside of a TypeScript application. If you are interested in contributing to ANTLR 4
itself, see CONTRIBUTING.md for contributor documentation.
End user requirements
Parsers generated by the ANTLR 4 TypeScript target have a runtime dependency on the
antlr4ts package. The package is tested and known to work with Node.js 6.7.
Development requirements
The tool used to generate TypeScript code from an ANTLR 4 grammar is written in Java. To fully utilize the ANTLR 4
TypeScript target (including the ability to regenerate code from a grammar file after changes are made), a Java Runtime
Environment (JRE) needs to be installed on the developer machine. The generated code itself uses several features new to
TypeScript 2.0.
- Java Runtime Environment 1.6+ (1.8+ recommended)
- TypeScript 2.0+
Getting started
- Install
antlr4ts
as a runtime dependency using your preferred package manager.
npm install antlr4ts --save
yarn add antlr4ts
- Install
antlr4ts-cli
as a development dependency using your preferred package manager.
npm install antlr4ts-cli --save-dev
yarn add -D antlr4ts-cli
-
Add a grammar to your project, e.g. path/to/MyGrammar.g4
-
Add a script to package.json for compiling your grammar to TypeScript
"scripts": {
// ...
"antlr4ts": "antlr4ts -visitor path/to/MyGrammar.g4"
}
-
Use your grammar in TypeScript
import { ANTLRInputStream, CommonTokenStream } from 'antlr4ts';
let inputStream = new ANTLRInputStream("text");
let lexer = new MyGrammarLexer(inputStream);
let tokenStream = new CommonTokenStream(lexer);
let parser = new MyGrammarParser(tokenStream);
let tree = parser.compilationUnit();
The two main ways to inspect the tree are by using a listener or a visitor, you can read about the differences between the two here.
Listener Approach
import { MyGrammarParserListener } from './MyGrammarParserListener'
import { FunctionDeclarationContext } from './MyGrammarParser'
import { ParseTreeWalker } from 'antlr4ts/tree/ParseTreeWalker'
class EnterFunctionListener implements MyGrammarParserListener {
enterFunctionDeclaration(context: FunctionDeclarationContext) {
console.log(`Function start line number ${context._start.line}`)
}
}
const listener: MyGrammarParserListener = new EnterFunctionListener();
ParseTreeWalker.DEFAULT.walk(listener, tree)
Visitor Approach
Note you must pass the -visitor
flag to antlr4ts to get the generated visitor file.
import { MyGrammarParserVisitor } from './MyGrammarParserVisitor'
import { AbstractParseTreeVisitor } from 'antlr4ts/tree/AbstractParseTreeVisitor'
class CountFunctionsVisitor extends AbstractParseTreeVisitor<number> implements MyGrammarParserVisitor<number> {
defaultResult() {
return 0
}
aggregateResult(aggregate: number, nextResult: number) {
return aggregate + nextResult
}
visitFunctionDeclaration(context: FunctionDeclarationContext): number {
return 1 + super.visitChildren(context)
}
}
const countFunctionsVisitor = new CountFunctionsVisitor()
countFunctionsVisitor.visit(tree)