tracing: Improve decoding of functions output

[klkvr]

Motivation

Currently, while decoding result of function execution in traces, the following is done:

1. If function appears in ABIs of some contract seen during execution and identified by it's bytecode, ABI is taken from this contract bytecode.
2. Otherwise, ABI is fetched from openchain.xyz

This works fine for decoding inputs, however, openchain.xyz does not (and can not) tell anything about output types of a function.

Due to this, outputs for any calls to external contract accessed by an interface in forked environment are not decoded at the moment.

An example of this behavior is following test:

pragma solidity 0.8.20;

import {Test} from "forge-std/Test.sol";

interface IERC20 {
    function balanceOf(address) external view returns (uint256);
}

contract TestTracing is Test {
    function test() public {
        vm.createSelectFork("mainnet");

        IERC20 usdc = IERC20(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);
        usdc.balanceOf(address(0));
    }
}

Traces for it will look like this:

  [15795] TestTracing::test()
    ├─ [0] VM::createSelectFork("mainnet")
    │   └─ ← 0x0000000000000000000000000000000000000000000000000000000000000000
    ├─ [9815] 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48::balanceOf(0x0000000000000000000000000000000000000000) [staticcall]
    │   ├─ [2529] 0xa2327a938Febf5FEC13baCFb16Ae10EcBc4cbDCF::balanceOf(0x0000000000000000000000000000000000000000) [delegatecall]
    │   │   └─ ← 0x0000000000000000000000000000000000000000000000000000000000000000
    │   └─ ← 0x0000000000000000000000000000000000000000000000000000000000000000
    └─ ← ()

However, it should be decoded into this:

  [15795] TestTracing::test()
    ├─ [0] VM::createSelectFork("mainnet")
    │   └─ ← 0
    ├─ [9815] 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48::balanceOf(0x0000000000000000000000000000000000000000) [staticcall]
    │   ├─ [2529] 0xa2327a938Febf5FEC13baCFb16Ae10EcBc4cbDCF::balanceOf(0x0000000000000000000000000000000000000000) [delegatecall]
    │   │   └─ ← 0
    │   └─ ← 0
    └─ ← ()

And this gets much uglier when working with contracts returning tuples/addresses/bytes

Solution

There is already with_events function which is used for importing events from known contracts when constructing a CallTraceDecoder, so I've just added similar logic for functions as well

foundry/crates/forge/bin/cmd/test/mod.rs

Lines 692 to 695 in fdad9fb

	let mut builder = CallTraceDecoderBuilder::new()
	.with_labels(result.labeled_addresses.iter().map(|(a, s)| (*a, s.clone())))
	.with_events(local_identifier.events().cloned())
	.with_verbosity(verbosity);

[DaniPopes]

Can you also add a test with the example contract? I don't believe we have trace-specific tests, so a repro with this PR's number is OK. I think we'll want to separate those tho.

[DaniPopes]

Also cc @onbjerg @Evalir tracing change

[DaniPopes]

@klkvr Sorry I meant repro tests in crates/forge/tests/it/repros.rs

[klkvr]

Hey @DaniPopes I am not sure if it makes sense to add this as a repro test

1. It seems to me that it isn't possible to get known_contracts object and configure trace identifier with it while not changing repro testing logic too much

2. Even if it is possible, the test will not really make much sense. I think test should check that

   traces are decoded correctly when testing through CLI

   rather than

   traces are decoded correctly when known contract abis are included into scope of call trace decoder

   The former is what this PR fixes, and the latter is how it does that, and this logic already worked before this PR

[mattsse]

this is great!

the integration test is appropriate since we want to check the actual formatted trace output