JS node.js parser does not start because of parser.MyStartRule()

Question

I'm using antlr4 (4.13) JS parser with node.js support and when I run the code, I get an error like this:

const tree = parser.MyStartRule();
^

TypeError: parser.MyStartRule is not a function

I don't know how to fix it. Thats my code:

Grammar: https://github.com/antlr/grammars-v4/blob/master/angelscript/angelscript.g4 Just for test (Dont change anything, only replace "grammar angelscript;" to "grammar fns;")

Code to run: (parse.js)

import antlr4 from 'antlr4';
import fnsLexer from './fnsLexer.js';
import fnsParser from './fnsParser.js';
import MyGrammarListener from './fnsListener.js';

const input = "func name(x) { say(x); } name("Hello world");";
const chars = new antlr4.InputStream(input);
const lexer = new fnsLexer(chars);
const tokens = new antlr4.CommonTokenStream(lexer);
const parser = new fnsParser(tokens);
const tree = parser.MyStartRule();

Run command: node parse.js

And my package.json:

{
  "name": "fns",
  "version": "1.0.0",
  "description": "",
  "main": "babel.config.js",
  "type": "module",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "antlr4": "^4.13.1-patch-1"
  }
}

I tried after this error to use chat-gpt to figure it out, and even downloaded the 4.9.0 version (this is the latest version that chat has caught), nothing helped.

Answer 1

As kaby mentioned in the comments: MyStartRule() is not a parser rule of your grammar. It is script:

grammar angelscript;

script
    : (
        import_
        | enum_
        | typdef
        | class_
        | mixin_
        | interface_
        | funcdef
        | virtprop
        | var_
        | func_
        | namespace
        | ';'
    )+ EOF
    ;

Use it instead:

const tree = parser.script();