Capture key name in reader exception where applicable

It would be very helpful to be able to generate a tiny bit more user friendly error messages that include the key in case of a value parsing error, so it’s easier for myself, but also an enduser to correct any input errors.

i.e. when a LocalDate has a wrong format, the following exception message is thrown: expected digit, offset: 0x0000012d

Looking at the macro generated code:

case 752419634 => if (in.isCharBufEqualsTo(l, "tradeDate"))
  {
    if (p0.&(65536).!=(0))
      p0.^=(65536)
    else
      in.duplicatedKeyError(l);
    _tradeDate = in.readLocalDate(_tradeDate)
}

I think there is an opportunity to wrap the last call (or the whole block that’s in the while loop) in a separate try/catch and enrich the thrown exception with the key name (tradeDate in this case).

The fact that the user knows which key has an error usually is enough. The error message itself can stay technical.

[momania]

Just wanted to leave a comment that I haven’t forgotten about this, but also haven’t looked into or thought about a way to make the error messages more user friendly. I’ll still keep using jsoniter-scala anyway, as it just works nicest of them all I think. Maybe, considering jsoniter-scala should stay high performance, it’s even an option to have an alternative parser that has very good error handling, and do a second parsing round with that one in case of errors. The performance penalty in an error case usually doesn’t matter anyway.

[jvican]

What worries me is the default behavior, though. I think we can improve it without compromising performance.