No name for properties in struct return data after calling contract

[aurelien-cuvelier]

Is there an existing issue for this?

• I have searched the existing issues

Package Version

1.19.0

Current Behavior

When calling a contract function which will return something more complex than a single value (basically a struct), the returned data won't be formatted correctly with the name of the returned properties.

When calling "slot0" on an Uniswap V3 pool:

const poolContract = getContract({
        abi: V3POOL_ABI,
        address: 'UNISWAP_V3_POOL_ADDR',
        publicClient: client,
      });
      
const slot0_res = await poolContract.read.slot0();

I get the following array prototype:

0:60315243730365501172258484916349n
1:132706
2:0
3:1
4:1
5:0
6:true

The result is the same when i use readContract directly from the client, or even after decoding the raw data from a client.call, using "decodeFunctionResult".

Expected Behavior

The expected behavior would have been to actually be able to call props in the return data by their name, just like ethersjs does:

sqrtPriceX96:60315243730365501172258484916349n
tick:132706
observationIndex:0
observationCardinality:1
observationCardinalityNext:1
feeProtocol:0
unlocked:true

Steps To Reproduce

Calling any contract's function which will return a struct.

Link to Minimal Reproducible Example (StackBlitz, CodeSandbox, GitHub repo etc.)

No response

Anything else?

No response

[jxom]

Please see https://viem.sh/docs/faq.html#why-is-a-contract-function-return-type-returning-an-array-instead-of-an-object

[jxom]

Though, you did mention that the function returns a struct. In which, it should decode as an object. Got an ABI that I can look at?

[jxom]

Looks like you may be running into this nuance with ABI compilation: https://x.com/_jxom/status/1645391096204369920

Maybe we could add a returnAs: “object” API or something for these cases.

[aurelien-cuvelier]

Though, you did mention that the function returns a struct. In which, it should decode as an object. Got an ABI that I can look at?

Sure, here is the ABI for the slot0:

  {
    inputs: [],
    name: 'slot0',
    outputs: [
      {internalType: 'uint160', name: 'sqrtPriceX96', type: 'uint160'},
      {internalType: 'int24', name: 'tick', type: 'int24'},
      {internalType: 'uint16', name: 'observationIndex', type: 'uint16'},
      {internalType: 'uint16', name: 'observationCardinality', type: 'uint16'},
      {
        internalType: 'uint16',
        name: 'observationCardinalityNext',
        type: 'uint16',
      },
      {internalType: 'uint8', name: 'feeProtocol', type: 'uint8'},
      {internalType: 'bool', name: 'unlocked', type: 'bool'},
    ],
    stateMutability: 'view',
    type: 'function',
  }