fix: prevent task deletion when files temporarily unavailable

[roomote]

Summary

This PR attempts to address Issue #11172 where parent tasks in delegation chains were being permanently deleted from task history when their api_conversation_history.json file was temporarily unavailable.

Problem

When getTaskWithId() was called and the task file was missing (due to disk I/O latency or race conditions during delegation transitions), the code unconditionally deleted the task from state, which:

• Orphaned child tasks in delegation chains
• Broke the "Back to Parent Task" navigation
• Caused permanent data loss

Solution

1. Removed the destructive deleteTaskFromState() call from getTaskWithId() - the primary fix
2. Added TaskFileMissingError and TaskNotFoundError error classes for proper error handling
3. Added retry logic with exponential backoff (3 retries, 100-400ms delays) for transient file I/O issues
4. Updated showTaskWithId() to show user-friendly error messages instead of deleting tasks
5. Updated deleteTaskWithId() to handle missing files gracefully using history metadata
6. Updated reopenParentFromDelegation() to recover from missing files by falling back to history metadata
7. Added hasDelegationMetadata flag to identify tasks with delegation relationships (parentTaskId, childIds, etc.)

Key Changes

• src/utils/errors.ts: Added TaskFileMissingError and TaskNotFoundError classes
• src/core/webview/ClineProvider.ts: Modified getTaskWithId(), showTaskWithId(), deleteTaskWithId(), and reopenParentFromDelegation()
• src/core/webview/__tests__/ClineProvider.taskHistory.spec.ts: Added comprehensive tests for new error handling behavior

Testing

• All existing tests pass (103 tests in total)
• Added 8 new tests covering:
  • TaskNotFoundError thrown when task does not exist
  • TaskFileMissingError thrown when file is missing
  • Task NOT deleted from history when file is missing
  • hasDelegationMetadata flag properly set for delegation chains
  • User-friendly error messages shown via vscode.window.showErrorMessage
  • Deletion works even when files are missing

Feedback and guidance are welcome!

---

Important

Fixes task deletion issue by adding error handling and retry logic for missing files in task history.

• Behavior:
  • Removed deleteTaskFromState() from getTaskWithId() to prevent task deletion when files are missing.
  • Added retry logic with exponential backoff in getTaskWithId() for file I/O issues.
  • Updated showTaskWithId() to display error messages instead of deleting tasks.
  • Updated deleteTaskWithId() to handle missing files using history metadata.
  • Updated reopenParentFromDelegation() to recover from missing files using history metadata.
• Errors:
  • Added TaskFileMissingError and TaskNotFoundError in errors.ts for better error handling.
• Testing:
  • Added tests in ClineProvider.taskHistory.spec.ts for new error handling and retry logic.

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[roomote]

Rooviewer   See task on Roo Cloud

Reviewed the changes. The implementation correctly addresses the issue of tasks being deleted when files are temporarily unavailable. Found one test quality issue:

• Test assertions may silently pass if getTaskWithId doesn't throw (lines 666-712 in test file)

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[roomote]

These tests use try-catch with assertions inside the catch block. If getTaskWithId doesn't throw (e.g., due to future mocking changes), the assertions won't run and the test will pass silently. Consider using expect.assertions(2) at the start of each test or refactoring to use await expect(...).rejects.toThrow(...) followed by a separate assertion for hasDelegationMetadata.

Suggested change

	it("includes hasDelegationMetadata flag when task has parentTaskId", async () => {
	await provider.resolveWebviewView(mockWebviewView)
	provider.isViewLaunched = true
	const historyItem = createHistoryItem({
	id: "child-task",
	task: "Child task",
	parentTaskId: "parent-task",
	})
	// Set up task history with this item
	;(mockContext.globalState.get as ReturnType<typeof vi.fn>).mockImplementation((key: string) => {
	if (key === "taskHistory") return [historyItem]
	return undefined
	})
	try {
	await provider.getTaskWithId("child-task")
	} catch (error) {
	expect(error).toBeInstanceOf(TaskFileMissingError)
	expect((error as TaskFileMissingError).hasDelegationMetadata).toBe(true)
	}
	})
	it("includes hasDelegationMetadata flag when task has parentTaskId", async () => {
	await provider.resolveWebviewView(mockWebviewView)
	provider.isViewLaunched = true
	const historyItem = createHistoryItem({
	id: "child-task",
	task: "Child task",
	parentTaskId: "parent-task",
	})
	// Set up task history with this item
	;(mockContext.globalState.get as ReturnType<typeof vi.fn>).mockImplementation((key: string) => {
	if (key === "taskHistory") return [historyItem]
	return undefined
	})
	const error = await provider.getTaskWithId("child-task").catch((e) => e)
	expect(error).toBeInstanceOf(TaskFileMissingError)
	expect((error as TaskFileMissingError).hasDelegationMetadata).toBe(true)
	})

_{Fix it with Roo Code or mention @roomote and request a fix.}