Branch coverage not returning correct value for branch coverage

[jatZama]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.2.0 (3d6bfdd 2023-12-16T00:20:53.761034000Z)

What command(s) is the bug in?

forge coverage

Operating System

macOS (Apple Silicon)

Describe the bug

I tested this contract :

// SPDX-License-Identifier: BSD-3-Clause-Clear

pragma solidity 0.8.22;

contract Branch {

    function branch(bool lhs, bool rhs) external returns (bool){
        bool result;
        if (lhs || rhs){
            result = true;
        }
        return result;
    }
}

With this simple test:

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.22;

import {Test, console2} from "forge-std/Test.sol";
import {Branch} from "../src/Branch.sol";

contract BranchTest is Test {
    Branch public branch;

    function setUp() public {
        branch = new Branch();
    }

    function test_branch() public {
        branch.branch(true,false);
    }
}

forge coverage (latest forge version, with default params) returns 100% coverage for % Branches, which is obviously incorrect. On the other hand, the saùe test returns 50% coverage with hardhat coverage which seems more correct.

[zerosnacks]

Related: #4314

I think there is a logical error in your test setup as you run the test once and there is no branching occuring as lhs evaluates, skipping over rhs.

if (lhs || rhs){
    result = true;
}

Rewriting the test as

contract Branch {
   function branch(bool foo) external returns (bool){
       bool result;
       if (foo) {
           result = true;
       } else {
           result = false;
       }
       return result;
   }
}

contract BranchTest is Test {
   Branch public branch;

   function setUp() public {
       branch = new Branch();
   }

   function test_branch() public {
       branch.branch(true);
   }
}

Correctly yields:

File	% Lines	% Statements	% Branches	% Funcs
src/Branch.sol	80.00% (4/5)	75.00% (3/4)	50.00% (1/2)	100.00% (1/1)
Total	80.00% (4/5)	75.00% (3/4)	50.00% (1/2)	100.00% (1/1)

Marking as resolved, #4314 is still an issue.