Output directory hash differs if the same build settings are applied via transition vs. command line #12171
Description
Description of the problem / feature request:
When the output directory hash for the bazel-out subdirectory for generated artifacts is computed on a transition, it is based upon a delta of the build settings before and after the transition. As a result, multiple output directories with different hashes are getting generated for targets that are built with the exact same build settings.
Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.
==> BUILD.bazel <==
load(":stuff.bzl", "fr")
fr(
name = "FW",
)
==> stuff.bzl <==
def _tr_impl(settings, attr):
return {
"//command_line_option:cpu": "ios_x86_64",
}
tr = transition(
implementation = _tr_impl,
inputs = ["//command_line_option:cpu"],
outputs = ["//command_line_option:cpu"],
)
def _fr_impl(ctx):
return []
fr = rule(
cfg = tr,
implementation = _fr_impl,
attrs = {
"_whitelist_function_transition": attr.label(
default = "@bazel_tools//tools/whitelists/function_transition_whitelist",
),
},
)
Run these commands:
> bazelisk cquery FW
# output includes "//sample:FW (3079a19075a19231a074cb24e8a1e6d40cc62546a3a4a625aed22fcbdfa6c465)"
> bazelisk cquery FW --cpu=ios_x86_64
# output includes "//sample:FW (e4ca851ff6d7872e00a13f59323655db1a538255f7c9f581cbc45ab47b005464)"
> bazelisk config 3079a19075a19231a074cb24e8a1e6d40cc62546a3a4a625aed22fcbdfa6c465 > /tmp/a
> bazelisk config e4ca851ff6d7872e00a13f59323655db1a538255f7c9f581cbc45ab47b005464 > /tmp/b
> diff /tmp/a /tmp/b
1,2c1,2
< BuildConfiguration 3079a19075a19231a074cb24e8a1e6d40cc62546a3a4a625aed22fcbdfa6c465:
< Skyframe Key: BuildConfigurationValue.Key[3079a19075a19231a074cb24e8a1e6d40cc62546a3a4a625aed22fcbdfa6c465]
---
> BuildConfiguration e4ca851ff6d7872e00a13f59323655db1a538255f7c9f581cbc45ab47b005464:
> Skyframe Key: BuildConfigurationValue.Key[e4ca851ff6d7872e00a13f59323655db1a538255f7c9f581cbc45ab47b005464]
24c24
< affected by starlark transition: [cpu]
---
> affected by starlark transition: []
79c79
< transition directory name fragment: ST-20f68df4034c
---
> transition directory name fragment: null
Observe that the transition directory name fragments are different, even though the other build settings are the same.
What operating system are you running Bazel on?
Mac OS 10.15.6.
What's the output of bazel info release?
release 3.5.0
If bazel info release returns "development version" or "(@Non-Git)", tell us how you built Bazel.
It does not include development version.
What's the output of git remote get-url origin ; git rev-parse master ; git rev-parse HEAD ?
I am not running bazel from a local git checkout of the bazel repo. I am using the release build.
Have you found anything relevant by searching the web?
The FunctionTransitionUtil.java file in bazel is intentionally computing the output directory hash only based upon the options that are affected by the starlark transition. It looks like this commit updated bazel to look at the delta of build settings: 6360ff7 cc @juliexxia
Any other information, logs, or outputs that you want to share?
In this branch, run repro.sh to reproduce the problem: https://github.com/segiddins/bazel-config-multiple-hashes.git
My team has confirmed this is a regression since bazel version 3.2.0.
In this PR, I also reproduced the problem: bazel-ios/rules_ios#124