How to make Rails 3 JSON parse doubly quoted strings and single number

Question

Background

On the json.org website, a string is defined as "char+" where char+ is one or more char. A char is any unicode character except " or \. A subset of control characters are allowed, just escape them:

"foo" "2" "\\"

In Javascript, if you want to parse a string, it needs to be enclosed:

"\"foo\"" or '"foo"', but not "'foo'"

In Rails 3, the JSON gem that runs C or pure Ruby code is default.

---

As per the accepted answer, the gem parses JSON documents rather than elements. A document is either a collection in the form of key, value (object/hash) or values (array).

The problem

Strings

Let's say we want to parse the string foo, We would need to enclose it as "\"foo\"" or '"foo"'

JSON.parse("\"foo\"")
JSON.parse('"foo"')

yield

JSON::ParserError unexpected token at '"foo"' 

meaning it can't parse "foo"

Numbers

The same goes for numbers: '3' or "3" will yield Needs at least two octets. Larger numbers ( an octet is a byte, so two utf8 characters are two bytes ): '42' or "42" simply yield the same JSON::ParserError unexpected token at '42'

The workaround

The gem correctly parses these things if they are in an array: '["foo"]' or '[3]'

jsonstring = '"foo"'
JSON.parse( "[#{jsonstring}]" )[0]

yields

"foo"

This is ridiculous. Am I not understanding something correctly? Or is this gem bugged?

Answer 1

json.org states:

JSON is built on two structures:

• A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.

• An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

Since "foo" is neither of the above you are getting the error message. To further concrete it have a look at Ruby JSON Parser, the documenation states:

To create a valid JSON document you have to make sure, that the output is embedded in either a JSON array [] or a JSON object {}. The easiest way to do this, is by putting your values in a Ruby Array or Hash instance.

Hence what you are mentioning as "workaround" is actually the correct way to parse a string using the JSON parser.

Additional Info:

Parsing "\"foo\"" on jsonlint.com and json.parser.online.fr raises an error, parsing ["foo"] passes the validation test on both the sites.