fix: ensure cancel button properly aborts streaming responses (#7014)

[roomote]

Summary

This PR fixes the issue where the Cancel button doesn't stop the response streaming process, even when chunks are arriving constantly.

Problem

As reported by @pwilkin in #7014, the Cancel button had no effect on streaming responses. Even with chunks arriving constantly (which should trigger the abort check between chunks), the cancellation didn't work. The investigation revealed that the abort flag wasn't being set properly before waiting for the stream to finish.

Root Cause

The issue was in ClineProvider.cancelTask():

1. It called cline.abortTask() which sets the abort flag
2. But then immediately waited for the stream to finish with pWaitFor
3. This created a race condition where the abort flag might not be properly propagated

Solution

1. Set abort flag immediately: In ClineProvider.cancelTask(), we now set cline.abort = true directly before calling abortTask()
2. Early abort check: Added an abort check at the beginning of the streaming loop, before processing any chunks
3. Proper cleanup: Added iterator cleanup when aborting the stream
4. Redundant checks: Kept the existing abort check after chunk processing for additional safety

Changes

• src/core/webview/ClineProvider.ts: Set abort flag immediately when cancel is clicked
• src/core/task/Task.ts: Check abort flag before and after processing each chunk, with proper iterator cleanup

Testing

• ✅ All existing tests pass
• ✅ Type checking passes
• ✅ Linting passes

Related Issues

Fixes #7014

---

Important

Fixes issue where Cancel button did not stop streaming tasks by setting abort flag immediately and adding early abort checks in ClineProvider.ts and Task.ts.

• Behavior:
  • Fixes issue where Cancel button did not stop streaming tasks in ClineProvider.ts and Task.ts.
  • Sets abort flag immediately in ClineProvider.cancelTask().
  • Adds early abort check before processing chunks in Task.ts.
  • Ensures iterator cleanup when aborting streams in Task.ts.
• Testing:
  • All existing tests pass.
  • Type checking and linting pass.

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[roomote]

Fixed the cancel button, but forgot to test if it actually wants to be clicked.

[roomote]

Consider adding tests for this critical cancel functionality to prevent regression. The fix looks good, but tests would verify:

• The abort flag is set immediately when cancel is clicked
• The early abort check works before processing chunks
• Iterator cleanup happens properly when aborting

[roomote]

The abort check and cleanup logic is duplicated here and at lines 1730-1747. Consider extracting this into a helper method like handleStreamAbort() to reduce duplication and ensure consistency:

Suggested change

	console.log(`aborting stream (early check), this.abandoned = ${this.abandoned}`)
	private async handleStreamAbort(iterator: AsyncIterator<any>, cancelReason: string) {
	console.log(`aborting stream (${cancelReason}), this.abandoned = ${this.abandoned}`)
	if (!this.abandoned) {
	await abortStream(cancelReason)
	}
	if (iterator.return) {
	await iterator.return(undefined).catch(() => {})
	}
	}

[roomote]

Minor: Could be more specific about the timeout duration:

Suggested change

	console.error("Failed to abort task gracefully")
	console.error("Failed to abort task gracefully within 3 second timeout")

[roomote]

Good fix! Setting the abort flag immediately before calling abortTask() eliminates the race condition. This ensures the flag is set even if the stream check happens before abortTask() propagates the flag internally.