Change state on specifik keyword Token.

[JulianKK]

Is it possible to Call next:stage when a keyword was metched?

[tjvr]

I'm afraid not!

But you can manually call lexer.setState after you see that keyword 🙂

_{Sent with GitHawk}

[evanpurkhiser]

Is there a simple way to do the manual setState call when using moo with nearley? 😉

[evanpurkhiser]

Here was my solution :)

const word = {
  match: /[^\s\n:]+:?/,
  type: moo.keywords({ filter })
};

const space = {
  match: /\s+/,
  lineBreaks: true
};

// Our lexer generates word and space tokens when in it's `main` state. A
// `filter` keyword may be produced by a matching word, in which case we move
// into the `keyValue` state.
//
// A `value` or `boolean` may be matched in the keyValue state, along with
// words and spaces. Any match here will return to the main state.

const lexer = moo.states({
  main: { word, space },
  keyValue: {
    value: { match: /"(?:\\["\\]|[^\n"\\])*"/, pop: 1 },
    boolean: { match: /(?:1|0)/, pop: 1 },
    word: { ...word, pop: 1 },
    space: { ...space, pop: 1 }
  }
});

// NOTE: There is currently no way to push state with moo when a keyword is
// matched [0]. We need to move to the `keyValue` lexer state after matching a
// filter, so we will patch the `next` function to push this state for us.
//
// [0]: https://github.com/no-context/moo/issues/115
const nextFn = lexer.next;

lexer.next = () => {
  const rv = nextFn.apply(lexer);

  if (rv && rv.type === "filter") {
    // TODO(ts): This method is missing from the type definitions. We can
    // remove the any cast when [0] is merged.
    //
    // [0]: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/43477
    (lexer as any).pushState("keyValue");
  }

  return rv;
};