tree fa5c8abe6f67b9fc0b80991947d98ad6a91f576c
parent 4e5b5b04ad6a56b635e9ef185976bcefd2b30de4
author jmmv <jmmv@google.com> 1584640304 -0700
committer Copybara-Service <copybara-worker@google.com> 1584640390 -0700

Delay creation of params files until we know where the writable execroot is.

When using workers or sandboxes, the output tree is not locked until the
spawn completes execution.  However, some virtual inputs, like params files,
have to be materialized before running the spawn.

The previous code was materializing these files directly into the output
tree without previously grabbing the dynamic execution lock, causing trouble.

To fix this, postpone the creation of these files until we know where the
writable execroot for a spawn is (which, when using workers or sandboxes is
in a location separate from the actual execroot).

This fix is gated behind --experimental_delay_virtual_input_materialization
so that we can roll it out separately from a release given the limited testing
we can do on builds that do local execution.  I'll remove the old code paths
once we have flipped the flag.

Problem diagnosed by felly@.

RELNOTES: None.
PiperOrigin-RevId: 301849551