ethers.BigNumber.from does not work with negative stringified bignumber

[KillariDev]

I have need to stringify a BigNumber and restore it. This seems to work with only with positive numbers and not negative

This fails:

ethers.BigNumber.from({ _hex: "-0x01", _isBigNumber: true })

while this works:

ethers.BigNumber.from({ _hex: "0x01", _isBigNumber: true })

Also this fails:

ethers.BigNumber.from(JSON.parse(JSON.stringify(ethers.BigNumber.from(-1))))

while this works:

ethers.BigNumber.from(JSON.parse(JSON.stringify(ethers.BigNumber.from(1))))

The workaround is to get the _hex string of the object and work with that, but I think it would be nice if this would work with the whole object.

[ricmoo]

The _ properties are meant to be internal and instantiation isn’t meant to operate quite in that way. Those properties may change in the future and they should not be depended upon. For example, I may soon add internal BigInt support for platforms that support it.

If your are serializing, you should consider using just value.toString() which would return the decimal value as a string or value.toHexString() which will return the hexadecimal value As a string. These strings should both work as you’d expect in BigNumber.from.

In general, you should not expect stringify to work on arbitrary classes...

Make sense?

[KillariDev]

I understand that they are intended to be internal, so the workaround there is not too nice.

I am using bigints in a bigger javascript object and its quite hand to be able to stringify whole thing and then get it back. The better workaround would be to iterate throught the structure and convert bigints using .toString(), or just use strings there all the time (but not as nice from dev experience perspective).

Is there are reason JSON.stringify couldn't be made to work or why it wouldn't be supported? If the support is not wanted, it would be handy to have .from() reject "{ _hex: "0x01", _isBigNumber: true }" as well so this would'nt cause weird bugs where it sometimes work and sometimes not.

[ricmoo]

I’ll look into adding a .toJSON method and test compatibility across implementations.

I plan to overhaul the internals of BigNumber, so relying on the above behaviour could just fail at some point in the future. I’m surprised that negative numbers don’t work (so I’ll prolly fix that too), but I’ll try getting a more sustainable solution in, in general. :)

[KillariDev]

That sounds like a good plan! I appreciate it :)

[ricmoo]

Added in 5.0.9. Let me know if it works for you.

I've added JSON support to the BigNumber class as well as support negative _hex_ just incase someone stored a serialized value in the old format. The _hex` support will be dropped in v6 (next summer).

Thanks! :)

[ricmoo]

Closing this now, but if you have any issues, please re-open.

Thanks! :)