Exception when multiple tasks concurrently access a finalizeValueOnRead property

[SaschaRiemer]

Current Behavior

Reading a property which is configured with finalizeValueOnRead() sometimes fails with this exception:

java.lang.UnsupportedOperationException: Valued object is in an unexpected state.	
	at org.gradle.api.internal.provider.ValueState$FinalizedValue.unexpected(ValueState.java:401)	
	at org.gradle.api.internal.provider.ValueState$FinalizedValue.forUpstream(ValueState.java:340)	
	at org.gradle.api.internal.provider.AbstractProperty.finalizeNow(AbstractProperty.java:281)	
	at org.gradle.api.internal.provider.AbstractProperty.lambda$beforeRead$0(AbstractProperty.java:276)	
	at org.gradle.api.internal.provider.ValueState.finalizeOnReadIfNeeded(ValueState.java:123)	
	at org.gradle.api.internal.provider.AbstractProperty.beforeRead(AbstractProperty.java:276)	
	at org.gradle.api.internal.provider.AbstractProperty.beforeRead(AbstractProperty.java:268)	
	at org.gradle.api.internal.provider.AbstractProperty.calculateOwnValue(AbstractProperty.java:162)	
	at org.gradle.api.internal.provider.AbstractMinimalProvider.calculateOwnPresentValue(AbstractMinimalProvider.java:80)	
	at org.gradle.api.internal.provider.AbstractMinimalProvider.get(AbstractMinimalProvider.java:100)	

Expected Behavior

Reading the property should be successful.

Context (optional)

A single extension exists on the rootProject. This allows configuring multiple tasks, one for each project, with a global configuration. Since the tasks have no dependencies between them, they can run in parallel.

Steps to Reproduce

An example project can be found at https://github.com/SaschaRiemer/gradle-concurrent-property
However, the error does not occur reliably. Execute "./gradlew myTask", and there is a chance that the build will fail with an exception. It can happen immediately, or take 50 tries, eventually, when executing the command often enough, it should occur.

However, after analyzing the source code, I believe the problem to be this:

• An extension is created on the rootProject, this extension has a ListProperty
• The property is configured as finalizeValueOnRead()
• For each project, a task is created. The task, during execution, accesses that property
• This can cause concurrent access to the property, because the tasks are executed in parallel.

Then, there is a race condition:

• Two threads, say Thread 1 and Thread 2, concurrently execute two of these tasks
• Both read the property, and first check whether the property needs to be finalized
• Since the property is not yet finalized, this check returns true for both tasks
• Thread 1 now finalized the value, i.e. it swaps AbstractProperty.state to a FinalizedValue
• Then, Thread 2 also tries to finalize the value, effectively calling ValueState.forUpstream on a FinalizedValue, which throws an exception

Gradle version

8.7

Build scan URL (optional)

No response

Your Environment (optional)

No response

[ov7a]

The issue is in the backlog of the relevant team and is prioritized by them.

[Sineaggi]

We've hit this in multiple projects.

[bamboo]

Related: #29140

[Sineaggi]

@bamboo is this expected then? Or an issue to be fixed?