Fix OnWindowExpirationContext.

[reuvenlax]

addresses #38875

[gemini-code-assist]

Summary of Changes

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This pull request introduces support for the OnWindowExpirationContext parameter within Apache Beam's DoFn framework. By updating the reflection-based invoker factory and signature validation logic, it enables users to access context-specific information during window expiration events, improving the flexibility of stateful processing.

Highlights

• Support for OnWindowExpirationContext: Added support for OnWindowExpirationContext as a parameter in DoFn methods, allowing access to window expiration information.
• Infrastructure Updates: Updated ByteBuddyDoFnInvokerFactory, DoFnInvoker, and DoFnSignature to handle the new parameter type across the reflection and invocation layers.
• Test Coverage: Updated ParDoTest and DoFnSignaturesTest to verify the correct injection and signature validation of OnWindowExpirationContext.

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[reuvenlax]

R: @ahmedabu98

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment assign set of reviewers

[gemini-code-assist]

Code Review

This pull request introduces support for the OnWindowExpirationContext parameter in @OnWindowExpiration methods of DoFn. It updates the reflection and code generation utilities, including ByteBuddyDoFnInvokerFactory, DoFnInvoker, and DoFnSignatures, to recognize, dispatch, and supply this parameter, and adds corresponding unit tests. There are no review comments, so I have no feedback to provide.

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[reuvenlax]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds support for the OnWindowExpirationContext parameter in @OnWindowExpiration methods of DoFn across runners, signature parsing, and invoker generation. The feedback suggests using JUnit's assertNotNull instead of Guava's Preconditions.checkNotNull in the unit tests to ensure idiomatic assertions and clearer test failures.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[gemini-code-assist]

In unit tests, it is more idiomatic to use JUnit's assertNotNull instead of Guava's Preconditions.checkNotNull. Preconditions.checkNotNull throws a NullPointerException (which JUnit treats as an unexpected error), whereas assertNotNull throws an AssertionError (which JUnit treats as a test failure), providing better integration with test runners and clearer test results.

Suggested change

	Preconditions.checkNotNull(context);
	assertNotNull(context);