coverage

name	coverage
description	Generate an HTML coverage report for all Go tests via bazel + genhtml, then open it in the browser.

Coverage

Before rendering, warn the user if genhtml is lcov 1.x (always the case on Windows msys2; also on older Linux distros). The output is degraded: LCOV_EXCL_* markers ignored (cgo helpers in bindings/go/* show 0%), flat index, all entries as absolute paths. Recommend rendering on Linux with lcov 2.x for the clean view.

1. Run coverage

bazelisk coverage --combined_report=lcov //...

Combined LCOV is at <bazel-cache>/execroot/_main/bazel-out/_coverage/_coverage_report.dat (printed at the end of the run). //cli/release/... installer targets are gated by target_compatible_with, so wrong-host toolchains skip automatically.

2. Render HTML

genhtml ships with lcov. Check the version with genhtml --version to pick the right command path below.

• Linux: apt install lcov / dnf install lcov / etc. 2.x available on Ubuntu 24.04+, Debian trixie+, Fedora 39+, current nixpkgs.
• Windows (msys2): pacman -S --noconfirm mingw-w64-clang-aarch64-lcov (or matching mingw-w64-*-lcov). Only ships 1.16.

Linux, lcov 2.x (preferred)

rm -rf /tmp/coverage-html && mkdir -p /tmp/coverage-html
unset SOURCE_DATE_EPOCH
genhtml --filter region --rc c_file_extensions=c,h,i,C,H,I,icc,cpp,cc,cxx,hh,hpp,hxx,go \
  --prefix "$(pwd)" --hierarchical \
  <lcov-path> -o /tmp/coverage-html

• --filter region + --rc c_file_extensions=...,go together honor // LCOV_EXCL_START/STOP/LINE markers. Drop either and the markers stop working.
• Unset SOURCE_DATE_EPOCH (set by nix / dpkg-buildpackage / etc. to a fixed epoch, used by lcov as "Test Date"). No-op in normal shells.
• --prefix "$(pwd)" anchors relative SF: paths to the repo root. Without it, lcov 2.x strips the longest common prefix (cli/), pushing bindings/go/* to absolute paths.
• --hierarchical renders a directory tree. Drop for a single flat index.

Linux lcov 1.x / Windows msys2 (degraded)

--filter, --rc, --hierarchical are 2.x-only — drop them. LCOV_EXCL_* markers are ignored, index is flat. Use --no-prefix (not --prefix): the auto prefix detection picks cli/ as the common root and renders bindings/go/* as absolute paths while everything else is relative — a half-stripped, inconsistent index. On Windows the mixed \ / / separators break it further. --no-prefix disables stripping entirely so every entry renders as a full absolute path — ugly but uniform.

Linux:

rm -rf /tmp/coverage-html && mkdir -p /tmp/coverage-html
unset SOURCE_DATE_EPOCH
genhtml --no-prefix <lcov-path> -o /tmp/coverage-html

Windows (msys2 bash, not PowerShell / cmd — genhtml is a Perl script and path translation happens inside msys2):

cd /c/Users/<you>/path/to/geniex
rm -rf /tmp/coverage-html && mkdir -p /tmp/coverage-html
/clangarm64/bin/genhtml --no-prefix <lcov-path> -o /tmp/coverage-html

Use /tmp (msys2 maps it to C:\msys64\tmp\), not $TEMP — $TEMP / $TMP are unset in msys2 bash, so -o "$TEMP/coverage-html" silently writes to /coverage-html. PowerShell's $env:TEMP is a different directory entirely.

3. Open the report

• Linux: xdg-open /tmp/coverage-html/index.html
• Windows (msys2 bash): start /tmp/coverage-html/index.html (or open C:\msys64\tmp\coverage-html\index.html from Explorer)

Notes

• For a single package use the target directly, e.g. //cli/internal/types:types_test.