Empty Alternative inside Nested Repetitions causes infinite loops on Parser initilization

I’m sure this was a grammar error on my part, but just wanted to let you know it’s possible to get into a loop state while performing self-analysis.

The loop is like this:

 at possiblePathsFrom (/git/chevrotain/src/parse/grammar/interpreter.ts:287:14)
    at getAlternativesForProd (/git/chevrotain/src/parse/grammar/interpreter.ts:265:24)
    at possiblePathsFrom (/git/chevrotain/src/parse/grammar/interpreter.ts:322:16)
    at getAlternativesForProd (/git/chevrotain/src/parse/grammar/interpreter.ts:265:24)
    at possiblePathsFrom (/git/chevrotain/src/parse/grammar/interpreter.ts:322:16)
    at getAlternativesForProd (/git/chevrotain/src/parse/grammar/interpreter.ts:265:24)

[bd82]

The phase that causes the infinite loop does not take into account the GATEs at all. I hope to have time on the weekend to debug the reproduce-able example farther.

[bd82]

I can reproduce the issue with this small example:

const { CstParser, createToken, EMPTY_ALT } = require("chevrotain")

// ----------------- lexer -----------------
const Comma = createToken({ name: "Comma", pattern: /,/ })

const allTokens = [
  Comma
]

class NestedManyEmptyAltBugParser extends CstParser {
  constructor() {
    super(allTokens)

    const $ = this

    // the parsing methods
    $.RULE("A", () => {
      $.MANY(() => {
        $.SUBRULE($.B)
      });
    });

    $.RULE("B", () => {
      $.MANY(() => {
        $.SUBRULE($.C)
      });
    });

    $.RULE("C", () => {
      $.OR([
        { ALT: () => $.CONSUME(Comma) },
        { ALT: () => EMPTY_ALT }
      ]);
    });

    this.performSelfAnalysis()
  }
}

const parser = new NestedManyEmptyAltBugParser()