Cancel DelayedClientCall when application listener throws

[jnowjack-lucidchart]

Align DelayedClientCall.DelayedListener with ClientCallImpl's existing behavior for listener exceptions. When the application listener throws from onHeaders/onMessage/onReady, catch the Throwable, cancel the call with CANCELLED (cause = the throwable), and swallow subsequent callbacks. When onClose throws, log and continue, matching ClientCallImpl.closeObserver. If onClose arrives from the transport after a prior callback threw, override its status/trailers with the captured CANCELLED so a server-supplied OK can't mask the local failure.

Previously, a throw from the application listener escaped to the callExecutor's uncaught-exception handler. The real call was not cancelled and the transport kept delivering callbacks to an already broken listener, different from how the same bug behaves on a normal ClientCallImpl, and a timing-dependent inconsistency depending on whether callbacks arrived before or after setCall + drain completed.

Trade-off: listener-callback throws are no longer visible to the executor's UncaughtExceptionHandler (they're attached as Status.cause instead). This matches ClientCallImpl and is the intended behavior.

Exception handling for the outer drainPendingCalls loop (realCall.sendMessage/request/halfClose/cancel) remains unaddressed; that TODO is preserved.

Note:
This change only handles exceptions thrown by the application listener. I don't try and solve the problems that #12737 is attempting to fix. My motivation is to fix the root cause behind bazelbuild/bazel#29316

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: jnowjack-lucidchart / name: Jacob Nowjack (8e59f3e)
• ✅ login: kannanjgithub / name: Kannan J (736f00a, bcaf12c)

[Copilot]

Pull request overview

This PR aligns DelayedClientCall.DelayedListener behavior with ClientCallImpl when the application ClientCall.Listener throws from callbacks, ensuring the call is cancelled and subsequent callbacks are suppressed/normalized instead of escaping to the executor’s uncaught exception handler.

Changes:

• Add exception-handling wrappers for onHeaders, onMessage, and onReady that cancel the call with CANCELLED (cause = thrown exception) and swallow later callbacks.
• Override transport-delivered onClose(Status.OK, …) after a prior listener exception to prevent server OK from masking a local failure; keep onClose exception behavior as “log and continue.”
• Add unit tests covering pending vs pass-through callback paths and the onClose override behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
core/src/main/java/io/grpc/internal/DelayedClientCall.java	Wraps listener callback dispatch to catch listener-thrown exceptions, cancel the real call, and normalize subsequent callbacks/onClose to match ClientCallImpl semantics.
core/src/test/java/io/grpc/internal/DelayedClientCallTest.java	Adds targeted tests for listener-throwing scenarios (pending + pass-through) and verifies cancellation + callback swallowing/onClose override.

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[kannanjgithub]

/gcbrun