extensions/typescript-language-features/src/tsServer/bufferSyncSupport.ts/BufferSynchronizer/updatePending
class BufferSynchronizer:	private updatePending(resource: vscode.Uri, op: BufferOperation): boolean {
		switch (op.type) {
			case BufferOperationType.Close:
				const existing = this._pending.get(resource);
				switch (existing?.type) {
					case BufferOperationType.Open:
						this._pending.delete(resource);
						return false; // Open then close. No need to do anything
				}
				break;
		}

		if (this._pending.has(resource)) {
			// we saw this file before, make sure we flush before working with it again
			this.flush();
		}
		this._pending.set(resource, op);
		return true;
	}