parse quoted string containing escaped quote

[jan zimmek]

hello,

i just found pegjs and started to test it, but run into trouble when
trying to parse a quoted string which contains escaped quote
characters.

this is my actual grammar:

// ---- START ----

start
= "{" (quoted_word)* "}"

quoted_word
= ' '? '"' word:word '"' { return word; }

word
= word:['a-z]+ { return word.join(''); }

// ---- END ----


but i want it to parse the following:


parser.parse('{"abc\"xyz"}');


the error following error occur:

{ name: 'SyntaxError',
message: 'Expected " ", "\\"" or "}" but "x" found.',
line: 1,
column: 7 }


any help would be really appreciated.

regards
jan

[Subbu Allamaraju]

I came across a similar issue in supporting escaped quotes in quoted strings. 

start = StringLiteral

StringLiteral = parts:(('"' DoubleString '"') / ("'" SingleString "'")) {

    return '"' + parts[1] + '"';

}

SingleString = c:([\u0020-\u0026]/[\u0028-\u005B]/[\u005D-\uFFFF]/[\\"])* {

    return c.join('');

}

DoubleString = c:([\u0020-\u0021]/[\u0023-\u005B]/[\u005D-\uFFFF]/[\\']/EscapedQuote)* {

    return c.join('');

}

EscapedQuote = [\u005c\u0022]

This grammar is unable to parse any strings.

What is the best way to support escaped strings?

Thanks for any direction.

Subbu

[Juan Felipe Garcia Catalan]

This seems to work for me, just handles double quotes, but should be easy to extend for singles:

str

    = "\"" str:(!unscapedquote anycharacter)* last:unscapedquote {

var r = "";

for (var c in str) {

   r += str[c][1];

}

return r + last; 

    }

unscapedquote

    = last:[^\\] "\"" {return last;}

anycharacter 

  = .

[Subbu Allamaraju]

Good idea. Thanks.

[David Majda]

2012/2/17 jan zimmek <jzi...@googlemail.com>:

> i just found pegjs and started to test it, but run into trouble when
> trying to parse a quoted string which contains escaped quote
> characters.

2012/4/9 Subbu Allamaraju <su...@subbu.org>:

> I came across a similar issue in supporting escaped quotes in quoted
> strings.

Have a look how this is handled e.g. in the JSON example grammar [1]
(look at the "string" rule and other rules it references).

[1] https://github.com/dmajda/pegjs/blob/master/examples/json.pegjs

--
David Majda
Entropy fighter
http://majda.cz/

[Subbu Allamaraju]

That works. Thanks.