Correctly convert a Float to a JsNumber using BigDecimal#decimal

[lars-n]

When converting Floats to a JsNumber they will not be converted exact. The issue appears to be in JsNumber.apply (https://github.com/spray/spray-json/blob/master/src/main/scala/spray/json/JsValue.scala#L97) where the Float should be converted to a BigDecimal using BigDecimal.decimal rather than BigDecimal (see documentation there).

see #109

[ktoso]

Verified that this indeed makes a difference, without it we'd get [error] '4.199999809265137' != '4.2' (BasicFormatsSpec.scala:46)

[ktoso]

Thanks!

[ktoso]

Failure seems to be MiMa, but not about any method that was touched in this PR... will fix separately

[ktoso]

2.10 build failed.

This addition would mean that we're not compatible with Scala 2.10 anymore.
Which perhaps is fine, but we need to manage expectations properly about the next release then...

https://travis-ci.org/spray/spray-json/jobs/302117152

[error] /home/travis/build/spray/spray-json/src/main/scala/spray/json/JsValue.scala:97: value decimal is not a member of object scala.math.BigDecimal
[error]     case _                 => new JsNumber(BigDecimal.decimal(n))
[error]                                                       ^
[error] one error found

[lars-n]

sry, forgot about 2.10. Changed the code to not use BigDecimal#decimal

[ktoso]

Nice, AFAICS that's correct (and what BigDecimal.decimal does inside anyway), let's have the tests pass but looking good

[lars-n]

tests seem to pass, but some other check failed

[lars-n]

let me know if there is anything else that needs to be changed

[lars-n]

@ktoso, any news on if/how/when this can be merged? It'd be useful for some cases here, not urgent though.

[jrudolph]

LGTM, thanks @lars-n even after all this time ;) (Rebased and removed whitespace changes)

[lars-n]

I already forgot about this one 😃 . Thanks @jrudolph