Starlark debugger crashes when a method references a symbol in the outer scope

[tpasternak]

Description of the bug:

Bazel throws:

ERROR: Debug server listener thread died: java.lang.NullPointerException: null value in entry: l=null
    at com.google.common.collect.CollectPreconditions.checkEntryNotNull(CollectPreconditions.java:33)
    at com.google.common.collect.ImmutableMapEntry.<init>(ImmutableMapEntry.java:54)
    at com.google.common.collect.ImmutableMap.entryOf(ImmutableMap.java:341)
    at com.google.common.collect.ImmutableMap$Builder.put(ImmutableMap.java:450)
    at net.starlark.java.eval.StarlarkThread$Frame.getLocals(StarlarkThread.java:192)
    at com.google.devtools.build.lib.starlarkdebug.server.DebugEventHelper.getScopes(DebugEventHelper.java:150)
    at com.google.devtools.build.lib.starlarkdebug.server.DebugEventHelper.getFrameProto(DebugEventHelper.java:139)
    at com.google.devtools.build.lib.starlarkdebug.server.ThreadHandler.lambda$listFrames$1(ThreadHandler.java:240)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(Unknown Source)
    at java.base/java.util.Collections$2.tryAdvance(Unknown Source)
    at java.base/java.util.Collections$2.forEachRemaining(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.copyInto(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
    at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.evaluate(Unknown Source)
    at java.base/java.util.stream.ReferencePipeline.collect(Unknown Source)
    at com.google.devtools.build.lib.starlarkdebug.server.ThreadHandler.listFrames(ThreadHandler.java:241)
    at com.google.devtools.build.lib.starlarkdebug.server.StarlarkDebugServer.listFrames(StarlarkDebugServer.java:187)
    at com.google.devtools.build.lib.starlarkdebug.server.StarlarkDebugServer.handleClientRequest(StarlarkDebugServer.java:162)
    at com.google.devtools.build.lib.starlarkdebug.server.StarlarkDebugServer.lambda$listenForClientRequests$0(StarlarkDebugServer.java:94)
    at java.base/java.lang.Thread.run(Unknown Source)%  

Which category does this issue belong to?

No response

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

Please just watch the movie:

https://github.com/user-attachments/assets/49e87337-470c-45eb-a438-8f7d15dce8ed

Which operating system are you running Bazel on?

No response

What is the output of bazel info release?

release 7.4.1

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

No response

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

No response

If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

No response

Have you found anything relevant by searching the web?

No response

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

No response

[meisterT]

cc @hvadehra