[Bug] Static call and function calls doesn't match whats in the function property

[ShravanSunder]

Issue with type generation

Using ethersv5 and typechain and hardhat

Below of is a snippet of a simple test contract:

contract YourContract {
  event SetPurpose(address sender, string purpose);
  string _purpose = 'Building Unstoppable Apps';

  constructor() {
    // what should we do on deploy?
  }

  function purpose() public view returns (string memory) {
    return _purpose;
  }

  function setPurpose(string memory newPurpose) public payable {

    _purpose = newPurpose;
    console.log(msg.sender, 'set purpose to', _purpose);
    emit SetPurpose(msg.sender, _purpose);
  }
}

Typechain generates a purpose function that has multiple return types. string and [string] as shown below.

This is what typechain generates

...
  functions: {
    purpose(overrides?: CallOverrides): Promise<[string]>;

    setPurpose(
      newPurpose: string,
      overrides?: PayableOverrides & { from?: string | Promise<string> }
    ): Promise<ContractTransaction>;
  };

  purpose(overrides?: CallOverrides): Promise<string>;

  setPurpose(
    newPurpose: string,
    overrides?: PayableOverrides & { from?: string | Promise<string> }
  ): Promise<ContractTransaction>;

  callStatic: {
    purpose(overrides?: CallOverrides): Promise<string>;

    setPurpose(newPurpose: string, overrides?: CallOverrides): Promise<void>;
  };
...

The return type of

functions: {
    purpose(overrides?: CallOverrides): Promise<[string]>;
}

does not match the static call and function call return type

  purpose(overrides?: CallOverrides): Promise<string>;

  callStatic: {
    purpose(overrides?: CallOverrides): Promise<string>;

    setPurpose(newPurpose: string, overrides?: CallOverrides): Promise<void>;
  };

Possible Cause

It seems to have to do with something with the target-ethers-v5 implementation of generateOutputTypes

https://github.com/ShravanSunder/TypeChain/blob/c0e175b3b6e8176d66bbbcc7f44e00987dd0e615/packages/target-ethers-v5/src/codegen/types.ts#L22-L28

export function generateOutputTypes(options: GenerateTypeOptions, outputs: Array<AbiOutputParameter>): string {
  if (!options.returnResultObject && outputs.length === 1) {
    return generateOutputType(options, outputs[0].type)
  } else {
    return generateOutputComplexType(outputs, options)
  }
}

[ShravanSunder]

@krzkaczor it looks like strings are considered objects and outputted as array of 1.

[ShravanSunder]

this is the log of what a string output variable in solidity is seen as in generateFunction

{
 |   name: 'purpose',
 |   inputs: [],
 |   outputs: [ { name: '', type: [Object] } ],
 |   stateMutability: 'view',
 |   documentation: undefined
 | } undefined
 |  { returnResultObject: true, useStructs: true } [ { name: '', type: { type: 'string', originalType: 'string' } } ]

this is only for functions that are under the property in a contract type

functions: {
...
}

[ShravanSunder]

here is a link to a reproduction: https://github.com/dethcrypto/TypeChain/pull/593/files#r778495210

[krzkaczor]

@ShravanSunder have you tested it? I just verified it and it's how ethers work -- for some reason functions. wrap result in an array. We have tests covering this behavior: https://github.com/dethcrypto/TypeChain/blob/master/packages/target-ethers-v5-test/test/DataTypesInput.test.ts#L47

I am gonna close it for now. Feel free to reopen if I am wrong.

and btw. this is controlled by this switch: https://github.com/dethcrypto/TypeChain/blob/master/packages/target-ethers-v5/src/codegen/index.ts#L81

[krzkaczor]

Please repoen if this is still a problem.