docs: fix misleading debugger support section in README#1054
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The README showed a plain py_binary with debugpy in deps and DEBUGPY_WAIT in env, implying this works out of the box. It doesn't — py_binary's launcher has no debugpy integration, so the env var is ignored. Users need the py_debuggable_binary macro from examples/debugger/ which generates a wrapper entrypoint that actually starts the debugpy listener. Update the README to clarify that a wrapper is required and point to the example for the full working setup.
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The Buildkite failure is unrelated to this PR — all 183 tests passed, but the build failed because the macOS SDK download from |
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Summary
The README's "Debugger Support" section shows a plain
py_binarywithdebugpyindepsandDEBUGPY_WAITinenv, implying this works out of the box. It doesn't —py_binary's Bash launcher has no debugpy integration, so the env var is set but nothing reads it. Users need thepy_debuggable_binarymacro fromexamples/debugger/which generates a wrapper entrypoint that actually starts the debugpy listener.This PR updates the README to:
debugpytodeps)examples/debugger/directory for the complete working setupContext
We hit this at CTC while setting up debugpy support in our monorepo. After following the README's instructions,
DEBUGPY_WAIT=1 bazelisk run //:appstarted the app without any debugger — the env var was silently ignored. We traced it to the launcher template (py_binary.tmpl.sh) which has noDEBUGPY_WAIThandling, and eventually found the working implementation inexamples/debugger/.We ended up porting the
py_debuggable_binarypattern into our build rules with one improvement: our version is runtime-gated — the debugpy listener only activates whenDEBUGPY_WAIT=1orDEBUGPY=1is set, making it safe to use on targets that are also deployed as OCI images (no open debug port in production). Happy to submit a follow-up PR to upstream this improvement, potentially as part of the ruleset itself rather than just an example, if there's interest.