Extract Event Args Utility Type

[fdarian]

Hi,

I have an idea on ExtractEventArgs utility types that might solves common problem on typing event.

Motivation

Coming from wagmi and TypeChain, as far as I know there isn't any way to extract fully typed event(s) from logs inside transaction receipt, assuming the contract/ABI has already been known. There are actually two possible solutions for this,

1. Using TypeChain generated event, here is an example of parsing receipt's log:

2. Using wagmi's watchContractEvent

The first solution might do the job, but we still need to hardcode the event name and manually cast to the desired event. Meanwhile the second solution which uses AbiType under the hood only facilitates "watching events" use-case, I still haven't found the AbiType's solution to type event from logs.

Solution

Therefore, I'm experimenting on ExtractEventArgs utility type that is used to extract AbiEvent's arguments by converting AbiEvent.inputs to a typed object. It also works alongside the ExtractAbiEvent.

Here's an example that parses ERC20 events.

Screen.Recording.2023-01-04.at.17.06.42.mov

Here's an example to type ethers LogDescription.

Screen.Recording.2023-01-04.at.17.18.12.mov

From the example above, I still need to cast to any first since I just quickly use TypeChain's generated code. In future, this helper type could be integrated to any upcoming wagmi features that provide automatic type inference. Something like getContractInferface(<abi>) or paseLogs(<abi>).

It's also possible to improve the current event or args that's currently still uses array. However, this might have some reasons that I'm not aware of why wagmi chose to use array instead of object.

Let me know what you guys think, happy to add a PR if this is useful.

Edited

Here's a better example on parsing log

[fdarian]

Hi,

I have an idea on ExtractEventArgs utility types that might solves common problem on typing event.

Motivation

Coming from wagmi and TypeChain, as far as I know there isn't any way to extract fully typed event(s) from logs inside transaction receipt, assuming the contract/ABI has already been known. There are actually two possible solutions for this,

1. Using TypeChain generated event, here is an example of parsing receipt's log:

2. Using wagmi's watchContractEvent

The first solution might do the job, but we still need to hardcode the event name and manually cast to the desired event. Meanwhile the second solution which uses AbiType under the hood only facilitates "watching events" use-case, I still haven't found the AbiType's solution to type event from logs.

Solution

Therefore, I'm experimenting on ExtractEventArgs utility type that is used to extract AbiEvent's arguments by converting AbiEvent.inputs to a typed object. It also works alongside the ExtractAbiEvent.

Here's an example that parses ERC20 events.

Screen.Recording.2023-01-04.at.17.06.42.mov

Here's an example to type ethers LogDescription.

Screen.Recording.2023-01-04.at.17.18.12.mov
From the example above, I still need to cast to any first since I just quickly use TypeChain's generated code. In future, this helper type could be integrated to any upcoming wagmi features that provide automatic type inference. Something like getContractInferface(<abi>) or paseLogs(<abi>).

It's also possible to improve the current event or args that's currently still uses array. However, this might have some reasons that I'm not aware of why wagmi chose to use array instead of object.

Let me know what you guys think, happy to add a PR if this is useful.

I just remember with TypeChain we can also use .queryFilter. But it requires contract.filter.<event-name>(), not handy if we need to parse transaction receipt coming from .wait()for example.

[gsteenkamp89]

@farreldarian
This is really awesome!
Not sure if you ever made this PR but I'd certainly make use of this if you're happy to share your code! 🙏

[fdarian]

Glad that you found it helpful!

I actually still waiting from @jxom, @tmm, or the rest from the community, whether this could be just an util, or maybe a breaking change for the next version.

[fdarian]

Quick correction, I forgot that Viem already has this feature already.

Anyway, where did you find it to be usefull? (assuming you are using viem)

[fdarian]

UPDATE 10 months later

10 months back we didn't have viem, but now the getContractEvents().args is fully typed!

I think this discussion can be closed

[gsteenkamp89]

I still needed this type helper so I did eventually find it. For those interested, Viem exports GetEventArgs.
One thing to note is that by default it excludes non-indexed args, so to get the exact same type that you get when calling useContractEvent:

import { GetEventArgs } from "viem";

type EventArgs = GetEventArgs<
  typeof abi,
  "EventName",
  { IndexedOnly: false } 
>;