lcov version 2.1 breaks coverage report

[0xernesto]

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 (c8db1e4 2024-06-27T00:18:32.026850000Z)

What command(s) is the bug in?

forge coverage --report lcov && genhtml lcov.info -o report --branch-coverage

Operating System

macOS (Apple Silicon)

Describe the bug

When trying to generate an HTML coverage report based on the lcov.info that forge coverage --report lcov outputs, the following error occurs:

Wrote LCOV report.
lcov: ERROR: (inconsistent) "src/MyContract.sol":49:  function MyContract. found on line but no corresponding 'line' coverage data point.  Cannot derive function end line.  See lcovrc man entry for 'derive_function_end_line'.
 (use "lcov --ignore-errors inconsistent ..." to bypass this error)

This problem happens if you install lcov using Homebrew on MacOS, which currently installs lcov version 2.1.

When downgrading to lcov version 1.16, this problem goes away.

To reproduce error:

brew install lcov
forge coverage --report lcov && genhtml lcov.info -o report --branch-coverage

To get around the error:
Downgrade lcov to version 1.16.

[grandizzy]

I think you can just forge coverage --report lcov && genhtml lcov.info -o report --rc lcov_branch_coverage=1 derive_function_end_line=0 as derive_function_end_line is enabled by default in lcov 2.1

[PierrickGT]

I've fixed the issue with the following command:
forge coverage --no-match-path 'test/invariant/**/*.sol' --report lcov && lcov --extract lcov.info --rc lcov_branch_coverage=1 --rc derive_function_end_line=0 -o lcov.info 'src/*' && genhtml lcov.info --rc branch_coverage=1 --rc derive_function_end_line=0 -o coverage

Locally I'm running:

• lcov: LCOV version 2.1-1
• genhtml: LCOV version 2.1-1

[grandizzy]

awesome, thanks for confirming, not sure if there's any code change we should do here or only document options to run coverage using LCOV versions > 1.16 (as lcov did for their tests backward compatibility linux-test-project/lcov@2bfaf3d#diff-bc9ca225569a229568d59f0551dc13b2fb4aa27b6815d0903adac1c17ba0899eR6-R8) @mattsse @DaniPopes @klkvr wdyt? thanks

[mattsse]

makes sense to me!

[grandizzy]

Docs updated with foundry-rs/book#1237

[DaniPopes]

This is fixed with #9438, making it possible to use LCOV 2.X without additional flags.