feat(storage): full object checksum: parse finalize_time and server crc32c in async object stream

[chandra-siri]

PR 1 of 3: Extract finalize_time and full_obj_server_crc32c from the response metadata in _AsyncReadObjectStream.open().

[gemini-code-assist]

Code Review

This pull request introduces tracking for object finalization and full object CRC32C checksums in the asynchronous read stream. The feedback focuses on simplifying the production code by removing logic added solely to accommodate unit test mocks (such as checking for a .seconds attribute). Instead, it is recommended to mock finalize_time as a standard datetime.datetime or None in the unit tests, which allows the production code to rely on standard isinstance checks.

[gemini-code-assist]

Avoid adding production code logic (such as checking for a .seconds attribute) solely to satisfy unit test mocks. In production, finalize_time is a datetime.datetime (or DatetimeWithNanoseconds) object. By updating the unit tests to mock finalize_time as a datetime.datetime instance (or None when unfinalized), we can simplify this logic significantly and keep the production code clean.

Suggested change

	# Since full object checksum validation is only required for finalized objects,
	# check finalize_time (which is DatetimeWithNanoseconds/datetime in production, or mocked in tests).
	finalize_time = getattr(response.metadata, "finalize_time", None)
	if finalize_time:
	is_finalized_val = False
	if isinstance(finalize_time, datetime.datetime):
	is_finalized_val = True
	elif hasattr(finalize_time, "seconds") and finalize_time.seconds > 0:
	is_finalized_val = True
	if is_finalized_val:
	self.is_finalized = True
	if hasattr(response.metadata, "checksums") and response.metadata.checksums:
	self.full_obj_server_crc32c = response.metadata.checksums.crc32c
	# Since full object checksum validation is only required for finalized objects,
	# check finalize_time (which is DatetimeWithNanoseconds/datetime in production).
	finalize_time = getattr(response.metadata, "finalize_time", None)
	if isinstance(finalize_time, datetime.datetime):
	self.is_finalized = True
	checksums = getattr(response.metadata, "checksums", None)
	if checksums:
	self.full_obj_server_crc32c = getattr(checksums, "crc32c", None)

[gemini-code-assist]

Mock finalize_time as an actual datetime.datetime instance instead of a mock with a .seconds attribute. This allows the production code to use standard isinstance checks without mock-specific workarounds. (Note: Ensure datetime is imported in this test file).

Suggested change

	recv_response.metadata.finalize_time.seconds = 12345
	recv_response.metadata.checksums.crc32c = 98765
	recv_response.metadata.finalize_time = datetime.datetime(2024, 1, 1, tzinfo=datetime.timezone.utc)
	recv_response.metadata.checksums.crc32c = 98765

[gemini-code-assist]

Set finalize_time to None to represent an unfinalized object, matching production behavior where the field is absent or unset.

Suggested change

	recv_response.metadata.finalize_time.seconds = 0 # NOT finalized!
	recv_response.metadata.finalize_time = None # NOT finalized!