antlr4ts

ANTLR 4 runtime for JavaScript written in Typescript

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antlr4ts - TypeScript/JavaScript target for ANTLR 4
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Overview

links to the distribution 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

  1. Install antlr4ts as a runtime dependency using your preferred package manager.
```bash npm install antlr4ts --save ``` ```bash yarn add antlr4ts ```
  1. Install antlr4ts-cli as a development dependency using your preferred package manager.
```bash npm install antlr4ts-cli --save-dev ``` ```bash yarn add -D antlr4ts-cli ```
  1. Add a grammar to your project, e.g. path/to/MyGrammar.g4
  1. Add a script to package.json for compiling your grammar to TypeScript
```
"scripts": {
// ...
"antlr4ts": "antlr4ts -visitor path/to/MyGrammar.g4"
}
```
  1. Use your grammar in TypeScript
```typescript
import { ANTLRInputStream, CommonTokenStream } from 'antlr4ts';
// Create the lexer and parser
let inputStream = new ANTLRInputStream("text");
let lexer = new MyGrammarLexer(inputStream);
let tokenStream = new CommonTokenStream(lexer);
let parser = new MyGrammarParser(tokenStream);
// Parse the input, where `compilationUnit` is whatever entry point you defined
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](https://github.com/antlr/antlr4/blob/master/doc/listeners.md).
###### Listener Approach
```typescript
// ...
import { MyGrammarParserListener } from './MyGrammarParserListener'
import { FunctionDeclarationContext } from './MyGrammarParser'
import { ParseTreeWalker } from 'antlr4ts/tree/ParseTreeWalker'
class EnterFunctionListener implements MyGrammarParserListener {
// Assuming a parser rule with name: `functionDeclaration`
enterFunctionDeclaration(context: FunctionDeclarationContext) {
console.log(`Function start line number ${context._start.line}`)
// ...
}
// other enterX functions...
}
// Create the listener
const listener: MyGrammarParserListener = new EnterFunctionListener();
// Use the entry point for listeners
ParseTreeWalker.DEFAULT.walk(listener, tree)
```
###### Visitor Approach
Note you must pass the `-visitor` flag to antlr4ts to get the generated visitor file.
```typescript
// ...
import { MyGrammarParserVisitor } from './MyGrammarParserVisitor'
import { AbstractParseTreeVisitor } from 'antlr4ts/tree/AbstractParseTreeVisitor'
// Extend the AbstractParseTreeVisitor to get default visitor behaviour
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)
}
}
// Create the visitor
const countFunctionsVisitor = new CountFunctionsVisitor()
// Use the visitor entry point
countFunctionsVisitor.visit(tree)
```