Not (not) capturing

[kans]

I'd like match any char that isn't a newline.

This works as expected:

> newline().pipe(not()).parse('\n')
ParjsFailure {
  trace: {
    userState: ParserUserState {},
    position: 0,
    reason: 'not expecting: expecting newline',
    input: '\n',
    location: [Getter],
    stackTrace: [ [Not] ],
    kind: 'Soft'
  }
}

In the following example, no input is consumed:

> newline().pipe(not()).parse('a')
ParjsFailure {
  trace: {
    userState: ParserUserState {},
    position: 0,
    reason: 'parsers did not consume all input',
    input: 'a',
    location: [Getter],
    stackTrace: [],
    kind: 'Soft'
  }
}

Is the intended way to write something like this using then?

>  newline().pipe(not()).pipe(then(anyChar())).parse('a')

[barona-mika-vilpas]

Hi 👋

I think you're right. Your second example creates a parser that cannot parse a newline (but does not parse anything else), and then that parser succeeds at failing to parse the newline. However, there is still text to parse, so parjs throws an error (you must handle all input by default).

You have two options:

it("can parse with anyChar()", () => {
    const p = newline().pipe(not(), qthen(anyChar()));
    expect(p.parse("a")).toBeSuccessful("a");
    expect(p.parse("\n")).toBeFailure(ResultKind.SoftFail);
});

it("can parse with must", () => {
    const p = anyChar().pipe(must(c => c !== "\n" || { kind: "Soft" }));
    expect(p.parse("a")).toBeSuccessful("a");
    expect(p.parse("\n")).toBeFailure(ResultKind.SoftFail);
});

[barona-mika-vilpas]

Closing this as it's been inactive for some weeks now. Feel free to reopen if needed.