Support toFixed method on BigNumbers

[rhlsthrm]

Description

web3.eth.abi.decodeLog now returns ethers.js BigNumber instances (which itself is inconsistent seeing as how Web3 removed BigNumber in favor of BN.js). These BigNumber instances do not support the method toFixed(). toString() can be unsafe, so we would like to only use toFixed(). Alternatively, support for getting the decoded data as strings instead of BigNumbers is an acceptable workaround.

Expected behavior

Calling bigNumberInstance.toFixed() should work.

Actual behavior

Calling bigNumberInstance.toFixed() returns an error.

Steps to reproduce the behavior

See Gist.

Error Logs

Gists

https://gist.github.com/rhlsthrm/9c198a5c4537a01fa521c97f0e785801

Versions

• web3.js: Beta 52
• nodejs:
• browser:
• ethereum node:

[princesinha19]

The BN.js library is only for integers that's why it doesn't support toFixed (). Can you explain why toString() can be unsafe?

[nivida]

We get the BigNumber object from ethers.js. Could you please open an issue in the ethers.js repository?

[bohendo]

@princesinha19 I see in the docs of bignumber.js that calling .toString() of a very large number might return a number in exponent-form which would likely cause problems & might be where the concern is coming from.

But the more recent version of ethers depends on bn.js which does not have this problem.

So looks like this might be a false alarm..?

[princesinha19]

Yes right @bohendo. But, it's a problem of ethers.js because we are using ethers.js for BigNumber Object so, I think this should be solved by ethers.js.

[rhlsthrm]

Yes @bohendo it looks like ethers calls it BigNumber but it's actually bn.js so it's not an issue.