Empty StringBuilder causes No state found: INIT EOF about klaxon

[haskellcamargo]

The behavior is correct, @ppamorim.
According to any JSON RFC specification, the first entry must be a JSON-valid expression. Empty string is a syntax error. No matches for ", {, [, \d, true, false or any other valid start token.

[haskellcamargo]

Almost every parser of JSON will throw unexpected end of input. A JSON parser will look for a valid start token, such as STRING, TRUE, FALSE, OPEN_BRACE, OPEN_BRACKET or QUOTE. But, in that case, after trying all these, the found token was EOF, therefore it was unexpected.

It's default behavior, as you can see on Chrome default JavaScript implementation.

[damphat]

Hi @ppamorim

According to http://www.json.org, empty string is not a valid json.

> JSON.parse("")
SyntaxError: Unexpected end of JSON input

If you want to add non-strict mode for klaxon then the Parser should return null for empty string.

[damphat]

parse("") MUST throws an error.

WHY?
There are a lot of projects that depends on klaxon, they may use that Exception for detecting error, validate user input, etc.

Even if you want to return null, you must explicitly provide an option for example:

val parser = Parser(Parser.NonStrict)
parser.parse("") // return null

[ppamorim]

@damphat Null means anything, we need to find a better solution for that fallback. Maybe returning Nothing?

[ppamorim]

@haskellcamargo The behavior is correct but the way that the library currently handles the exception doesn't help. Returning a null or nothing can be better.

[ppamorim]

It can use a clear Exception for a strict configuration, it's more sensible. I noticed that the parser does a lot of verification/setup and then thrown the error. Is that correct?

[ppamorim]

@damphat I did changes on my pull request. Would you like to have a look on it? Thank you.