This project is a typescript parser implementation for Pkl. It is designed to parse Pkl code using antl4ng and typescript.
To install the parser, run the following command:
pnpm add @pkl-ts/parserThe following example shows how to parse a string input to a parse tree:
import { pklParser } from '@pkl-ts/parser';
import { CharStreams } from '@pkl-ts/parser/antlr';
const input = `
age = 22
name: String = "Steve Jobs"
job {
title = "CEO"
company = "Apple"
yearsOfExperience = 1
}
`;
const tree = pklParser(CharStreams.fromString(input));You can then use the generated parser to walk the parse tree, for example with a visitor to extract all classProperty of Pkl code in array format:
import { ClassPropertyContext, PklTsParserVisitor } from '@pkl-ts/parser';
class Visitor extends PklTsParserVisitor<Array<string>> {
visitClassProperty = (ctx: ClassPropertyContext) => {
let name = ctx.Identifier().getText();
return [name];
};
protected defaultResult(): Array<string> | null {
return null;
}
protected aggregateResult(
aggregate: Array<string> | null,
nextResult: Array<string> | null,
): Array<string> | null {
if (aggregate === null) {
return nextResult;
} else if (nextResult === null) {
return aggregate;
} else {
return aggregate.concat(nextResult);
}
}
}
let ri = tree.replInput();
let visitor = new Visitor();
visitor.visit(ri);
let classProperties = visitor.visit(ri);
console.log(classProperties); // ['age', 'name', 'job']Also, you can walk the parse tree with listener too:
import { ClassPropertyContext, PklTsParserListener } from '@pkl-ts/parser';
import { ParseTreeWalker } from '@pkl-ts/parser/antlr';
class Listener extends PklTsParserListener {
classProperties: string[] = [];
enterClassProperty = (ctx: ClassPropertyContext) => {
let name = ctx.Identifier().getText();
this.classProperties.push(name);
};
}
let ri = tree.replInput();
let listener = new Listener();
ParseTreeWalker.DEFAULT.walk(listener, ri);
console.log(listener.classProperties); // ['age', 'name', 'job']Or get value from tree directly
let ri = tree.replInput();
let classProperties: string[] = [];
ri.classProperty().forEach((ctx) => {
let name = ctx.Identifier().getText();
classProperties.push(name);
});
console.log(classProperties); // ['age', 'name', 'job']