Boa: Default number formatting is not spec compliant

[HalidOdat]

Describe the bug

Currently we use the default native Rust formatter to format floating-point numbers, which is not spec compliant.

To Reproduce
Steps to reproduce the issue, or JavaScript code that causes this failure.

This JavaScript code reproduces the issue:

0.0000001
3.e50

Expected behavior

In this scenario we should get 1e-7 and 3e+50 back.
Actual output is 0.0000001 and 300000000000000000000000000000000000000000000000000.

Build environment (please complete the following information):

• OS: Manjaro Linux
• Target triple: x86_64-unknown-linux-gnu
• Rustc version: 1.43.1 (8d69840ab 2020-05-04)

Additional context

We need to write our own f64 formatter like V8 DoubleToCString (see V8 implementation link bellow)

You can find more information:

• ECMAScript spec
• V8 implementation
• V8 Tests

[Tropid]

I can take this if nobody else wants it :)

[HalidOdat]

I can take this if nobody else wants it :)

Sure! Tell us if you need any help, or if you have any questions