Crash with empty value of --repo_env

[layus]

Description of the bug:

When a --repo_env var lacks the value part, Bazel crashes instead of using the value of that variable from the environment.

Starting local Bazel server and connecting to it...
Loading: 0 packages loaded
FATAL: bazel crashed due to an internal error. Printing stack trace:
java.lang.RuntimeException: Unrecoverable error while evaluating node 'REPOSITORY_DIRECTORY:@debug' (requested by nodes 'IGNORED_PACKAGE_PREFIXES:@debug')
	at com.google.devtools.build.skyframe.AbstractParallelEvaluator$Evaluate.run(AbstractParallelEvaluator.java:674)
	at com.google.devtools.build.lib.concurrent.AbstractQueueVisitor$WrappedRunnable.run(AbstractQueueVisitor.java:382)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: java.lang.NullPointerException: null value in entry: FOO=null
	at com.google.common.collect.CollectPreconditions.checkEntryNotNull(CollectPreconditions.java:32)
	at com.google.common.collect.RegularImmutableMap.fromEntryArray(RegularImmutableMap.java:99)
	at com.google.common.collect.RegularImmutableMap.fromEntries(RegularImmutableMap.java:73)
	at com.google.common.collect.ImmutableMap.copyOf(ImmutableMap.java:460)
	at com.google.common.collect.ImmutableMap.copyOf(ImmutableMap.java:433)
	at com.google.devtools.build.lib.bazel.repository.starlark.StarlarkRepositoryFunction.fetch(StarlarkRepositoryFunction.java:174)
	at com.google.devtools.build.lib.rules.repository.RepositoryDelegatorFunction.fetchRepository(RepositoryDelegatorFunction.java:415)
	at com.google.devtools.build.lib.rules.repository.RepositoryDelegatorFunction.compute(RepositoryDelegatorFunction.java:349)
	at com.google.devtools.build.skyframe.AbstractParallelEvaluator$Evaluate.run(AbstractParallelEvaluator.java:590)
	... 4 more

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

Create a trivial repository_rule that uses the env variable.

───────┬───────────────────────────────────────────────
       │ File: BUILD   <EMPTY>
       │ Size: 0 B
───────┴───────────────────────────────────────────────
───────┬───────────────────────────────────────────────
       │ File: main.bzl
       │ Size: 198 B
───────┼───────────────────────────────────────────────
   1   │ 
   2   │ def _dump_env(ctx):
   3   │     val = ctx.os.environ.get("FOO", "nothing")
   4   │     print("FOO", val)
   5   │     ctx.file("FOO", val)
   6   │ 
   7   │ 
   8   │ dump_env = repository_rule(
   9   │     implementation = _dump_env,
  10   │     local = True,
  11   │ )
  12   │ 
───────┴───────────────────────────────────────────────
───────┬───────────────────────────────────────────────
       │ File: WORKSPACE
       │ Size: 65 B
───────┼───────────────────────────────────────────────
   1   │ load("//:main.bzl", "dump_env")
   2   │ 
   3   │ dump_env(
   4   │     name = "debug",
   5   │ )
───────┴───────────────────────────────────────────────

bazel build @debug//:foo

Which operating system are you running Bazel on?

Linux (NixOS)

What is the output of bazel info release?

release 5.1.1- (@non-git)

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

Bazel 5.1.1, built with nix, on NixOS.

Not tested yet if this is nix/nixos specific.

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

fatal: not a git repository (or any of the parent directories): .git
fatal: not a git repository (or any of the parent directories): .git
fatal: not a git repository (or any of the parent directories): .git

Have you found anything relevant by searching the web?

Seems like the feature is used to be broken: #12886

See also #8869

Any other information, logs, or outputs that you want to share?

No response

[layus]

Seems like the underlying library started refusing null entries while the code relies on them to encode the case where no value is passed and the real value must be taken from the environment.

[layus]

Oh, it seems my report lacks the most important part: the actual --repo_env=FOO flag.

You can change the command line to FOO=bar bazel build @debug//:test --repo_env=FOO, or use a .bazelrc like I did.

I had to deep clean everything before reproducing again:

bazel clean --expunge
bazel shutdown
rm -rf ~/.cache/bazel

[meteorcloudy]

Fixed by ed886ee