How to get trimmed string with a simple solution? about dart-petitparser HOT 6 CLOSED

Order matters. The following parser should do what you want:

word().plus().flatten().trim()

Have a look at the documentation of flatten() and trim() and check out the implementation of the two parsers to understand why that is.

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It seems doesn't work:

word().plus().flatten().trim()

The whitespaces are still there. I have to write it like:

word().plus().flatten().map((x) => x.trim());

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I've added tests for both variations and everything is as expected: 62da932.

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What about a complex one?

    Parser whitespaceInLine() => char('\n').not() & whitespace();
    var ppp = word().plus().trim(whitespaceInLine()).flatten().trim();

    var rs = ppp.parse("   abc  ");
    print("[${rs.value}]");

It prints:

[abc  ]

I think if we can change the flatten() method as:

flatten([bool trim = false])

Because I think trim a string is a very common requirement.

PS: I love your PetitParserDart very much, that I can't write my Dart code without it, thank you !

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Again, flatten() does not work on the result of the inner parser, but it discards that result and returns the the range in the input buffer the inner parser consumed (see the documentation and the implementation of the FlattenParser). If there is a trim() parser inside the flatten(), then you end up with the whitespace that the trimmer consumed as well. If trim() is outside the flatten(), the whitespace are consumed before and after the flatten() kicks in.

So you need to flatten() where you want the input to be flattened. That is, in your example directly after word().plus(). If you change your example to

var ppp = word().plus().flatten().trim(whitespaceInLine());

it works.

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Thanks, I understand it now

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