Translate compile_commands.json in Bazel

[skhal]

lab/refresh_commands

Lines 11 to 15 in baf7f2b

	sed \
	-i'' \
	-e 's,/usr/bin/clang-21,/usr/local/bin/clang21,' \
	-e 's,/usr/lib/llvm-21,/usr/local/llvm21,' \
	compile_commands.json

Instead of updating compile commands with sed(1) in a script, let Bazel update the commands.

The rule should have source (/usr) and target (/usr/local) paths configurable.

[skhal]

Naive attempts [failed]

• ❌ tried to write a rule to process outputs of refresh_compile_commands() - failed because the latter one is a macro, not a rule with outputs
• ❌ tried to create symbolic links in /usr/local/ with llvm. Bazel does work with /usr/local/bin/clang21 (it is present in the compile_commands.json) but still resolves the link from /usr/local/llvm/.../include/... to /usr/lib/llvm-21/.... The resulting compile_commands.json is a mix of two worlds

Road blockers

1. Hedron Vision was acquired by Google Deep Mind, i.e., bazel-compile-commands-extractor future support is unknown (ref, announcement).
2. Apparently refresh_compile_commands() is macro that wraps a Python binary, e.g. it is not a Bazel rule with declared outputs that others may use for further processing to generate compile_commands.json.

Status quo

The issues hang in bazel-compile-commands-extractor since about 2024, the project seem to be pretty much abandoned.

Options

1. [short-term] Fork bazel-compile-commands-extractor, refactor the macro to extract a rule that others may use
2. [long-term] Write own compile commands extractor.

[skhal]

The compile commands extractor runs an Aquery to access actual build commands:

% bazel aquery "mnemonic('CppCompile', deps(//iq/1/twosum/...))" \
    --output=jsonproto \
    --include_artifacts=false \
    --ui_event_filters=-info \
    --noshow_progress \
    --features=complier_param_file \
    --features=-layering_check \
    --host_features=-compiler_param_file \
    --host_features=-layering_check