fix(functions): invalidate URLSession in streamed response

[AndroidPoet]

What

_invokeWithStreamedResponse creates a per-call, delegate-backed URLSession. A delegate-backed URLSession keeps a strong reference to its delegate until the session is explicitly invalidated (Apple docs: "the session object keeps a strong reference to the delegate until your app exits or explicitly invalidates the session").

Today onTermination only cancels the task and holds _ = delegate, but never invalidates the session:

continuation.onTermination = { _ in
  task.cancel()
  // Hold a strong reference to delegate until continuation terminates.
  _ = delegate
}

So every streamed invocation leaks a URLSession and its StreamResponseDelegate (which retains the stream continuation) permanently — even after the caller stops consuming. Apps that open streaming edge functions repeatedly accumulate them unbounded.

Fix

Invalidate the session when the stream terminates. invalidateAndCancel() cancels the outstanding task and releases the session's reference to the delegate, so task.cancel() / the _ = delegate hack are no longer needed:

continuation.onTermination = { _ in
  session.invalidateAndCancel()
}

This mirrors the fix already merged for the Realtime web-socket session in #1080 (fix(realtime): invalidate URLSession when web socket closes).

Testing

Added testInvokeWithStreamedResponseInvalidatesSession, which weak-references the stream delegate and asserts it deallocates after the stream terminates. It fails on main (delegate leaks — assertion fails after the poll window) and passes with this change (delegate freed almost immediately). To observe the delegate's lifetime the streamed setup is factored into an internal streamResponse(_:options:) that also returns the delegate; the public _invokeWithStreamedResponse signature is unchanged.

• swift test --filter FunctionsTests — 29 passing
• ./scripts/format.sh — clean

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 3c5dedb4-a0aa-449f-8e43-663523ada0f1

📥 Commits

Reviewing files that changed from the base of the PR and between b118484 and 36cd42b.

📒 Files selected for processing (2)

• Sources/Functions/FunctionsClient.swift
• Tests/FunctionsTests/FunctionsClientTests.swift

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Improved cleanup when streamed function responses finish or terminate.
  • Ensured associated network resources are properly released after streaming completes.

• Tests

  • Added coverage verifying that streamed response resources are released within the expected timeframe.

Walkthrough

FunctionsClient now creates streamed function responses through a streamResponse helper that returns both the AsyncThrowingStream and its delegate. When streaming terminates, the owning URLSession is invalidated and cancelled instead of directly cancelling the data task. A new async test consumes the stream and verifies that the delegate is subsequently deallocated.

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