Null pointer exception when using @local_config_platform//:host

[uhthomas]

Description of the problem / feature request:

Bazel crashes when using a rule with:

target_compatible_with =  ["@local_config_platform//:host"],

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

Create a target and amend it to include the above snippet. Try building it.

What operating system are you running Bazel on?

linux/amd64

What's the output of bazel info release?

release 4.0.0- (@non-git)

Have you found anything relevant by searching the web?

Not really. I couldn't find this stack trace anywhere.

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

FATAL: bazel crashed due to an internal error. Printing stack trace:
java.lang.RuntimeException: Unrecoverable error while evaluating node 'ConfiguredTargetKey{label=//test/integration:integration_test, config=BuildConfigurationValue.Key[00fda4c88c6c21307a074c88f10f7f34629019485e5426f1494f953a133c75a0]}' (requested by nodes )
        at com.google.devtools.build.skyframe.AbstractParallelEvaluator$Evaluate.run(AbstractParallelEvaluator.java:563)
        at com.google.devtools.build.lib.concurrent.AbstractQueueVisitor$WrappedRunnable.run(AbstractQueueVisitor.java:398)
        at java.base/java.util.concurrent.ForkJoinTask$AdaptedRunnableAction.exec(ForkJoinTask.java:1407)
        at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
        at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
        at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
        at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
        at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)
Caused by: java.lang.NullPointerException
        at com.google.devtools.build.lib.analysis.platform.ConstraintCollection.hasConstraintValue(ConstraintCollection.java:216)
        at com.google.devtools.build.lib.analysis.RuleContext.targetPlatformHasConstraint(RuleContext.java:1226)
        at com.google.devtools.build.lib.analysis.constraints.RuleContextConstraintSemantics.lambda$incompatibleConfiguredTarget$1(RuleContextConstraintSemantics.java:904)
        at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:176)
        at com.google.common.collect.CollectSpliterators$1.lambda$forEachRemaining$1(CollectSpliterators.java:120)
        at java.base/java.util.AbstractList$RandomAccessSpliterator.forEachRemaining(AbstractList.java:720)
        at com.google.common.collect.CollectSpliterators$1.forEachRemaining(CollectSpliterators.java:120)
        at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
        at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
        at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
        at com.google.devtools.build.lib.analysis.constraints.RuleContextConstraintSemantics.incompatibleConfiguredTarget(RuleContextConstraintSemantics.java:905)
        at com.google.devtools.build.lib.analysis.ConfiguredTargetFactory.createRule(ConfiguredTargetFactory.java:327)
        at com.google.devtools.build.lib.analysis.ConfiguredTargetFactory.createConfiguredTarget(ConfiguredTargetFactory.java:194)
        at com.google.devtools.build.lib.skyframe.SkyframeBuildView.createConfiguredTarget(SkyframeBuildView.java:938)
        at com.google.devtools.build.lib.skyframe.ConfiguredTargetFunction.createConfiguredTarget(ConfiguredTargetFunction.java:1013)
        at com.google.devtools.build.lib.skyframe.ConfiguredTargetFunction.compute(ConfiguredTargetFunction.java:371)
        at com.google.devtools.build.skyframe.AbstractParallelEvaluator$Evaluate.run(AbstractParallelEvaluator.java:477)
        ... 7 more

[uhthomas]

I see the same behaviour with @bazel_tools//platforms:host_platform.

My .bazelrc is identical to this.

[katre]

The underlying issue here is that target_compatible_with is expecting targets from the rule constraint_value, and @local_config_platform//:host is a platform.

It still shouldn't crash, so I will investigate that so that users can get a useful error message.

What are you actually trying to do? If you just want to know what constraints are used in the auto-detected host platform, you can do the following:

load("@local_config_platform//:constraints.bzl", "HOST_CONSTRAINTS")

...
target_compatible_with = HOST_CONSTRAINTS,
...

[katre]

The crash was fixed in 24d0864 (making this a duplicate of #12879).

Conveniently for you, that commit was cherrypicked to the just-released Bazel 4.1.0, so upgrade to that, fix your target_compatible_with, and you should be good to go.