tree ecd48fc990117090abe0e4c6a17c7df5f6a60828
parent e008d728cdd58f047094136f04e4a9217ef4390e
author David 'Digit' Turner <digit@fuchsia.infra.roller.google.com> 1631926675 +0000
committer Copybara-Service <copybara-worker@google.com> 1631926750 -0700

[roll] Roll fuchsia [build] Ensure `fx build` works with action tracing

When setting `build_should_trace_actions=true` in `args.gn` to
enable action tracing, the `fx build` command will fail because
some dart tools read from or write to `out/default/.dart/dartdev.json`,
which isn't listed as a valid input or output by any action.

This comes from the `dartdev` library which uses '$HOME/.dart' to
store various settings, and `hermetic-env` (used by `fx build`)
that sets up an environment without HOME defined!

As a consequence, dartdev writes to the current directory,
i.e. the build directory, hence the illegal access caught by the
action tracer.

This does not happen when using `fx ninja -C out/default` directly,
which is what our infra bots do use (through `fint`). Hence why they
never see this error.

This CL adds an exception to the action tracer to ignore accesses
to '${root_build_dir}/.dart'. An alternative would be to modify
`hermetic-env` to setup a fake HOME directory, but this allows
future actions in the build to write silenty to it without being
detected, which is undesirable.

For testing, `build/tracer/action_tracer_test.py` was run successfully,
as well as `fx build` with action tracing enabled.

Original-Bug: None
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/582641
Original-Revision: 32a781b76d646b4e777501bb766c8657bdbb97df
GitOrigin-RevId: db49ea83b24d68a9d589cde5e29755eaefee4a34
Change-Id: Iff5f6b97e4b85fc576eae390bd8d98845e696e2d