Optionally allow leading decimal in float tokens

[jamesagnew]

JSON doesn't allow a leading decimal in a float (e.g. { "someval": .123 } ) and Jackson rightly errors out when you try to parse this.

I have a need however (mostly caused by a previous Gson implementation now replaced with Jackson in HAPI FHIR silently accepting this syntax) to parse JSON containing this invalid format.

The attached pull request adds a read feature enabling the parsing of these leading decimal points.

[cowtowncoder]

@jamesagnew I thought I added a comment here but looks like I did not. So, I think this makes sense: I'll have a look and may be able to merge this to be included in 2.11 (will cherry-pick from master commit, should be fine).
Thank you for submitting the patch.

But one thing I would need (if I haven't yet asked for it; I don't think I have) before merging the patch is CLA. It's found from

https://github.com/FasterXML/jackson/blob/master/contributor-agreement.pdf

and is usually easiest to print, fill & sign, scan/photo, email to info at fasterxml dot com.
This is only needed once before the first contribution, one is fine for any and all submissions.

Thank you once again!

[jamesagnew]

Thanks @cowtowncoder! CLA has been signed and submitted.

[cowtowncoder]

Quick note: with CLA, I am proceeding this one -- but merging pieces manually, mostly due to challenges b/w master and 2.11 branches (wrt refactoring of JsonReadFeature / JsonParser.Feature). Should be done soon.

[cowtowncoder]

Finally got it all done; added async-parser tests too (those are separate as input source is different). Thank you again for contributing this! Hoping to now release 2.11.0 by the end of the week.

[jamesagnew]

@cowtowncoder Appreciate the fast response to a random PR from a new contributor! You're better at this than I am. :)

[cowtowncoder]

@jamesagnew I've had some experience. But the patch was good and made this pretty easy. Adding new support for non-standard parsing is often tricky due to my over-optimization coding habits, but this turned out to be easier than I'd have expected. :)

Thank you once again for contributing this!