fix: revise blob.compose query parameters if_generation_match (#454)

* revise blob.compose logic to match API usage * update tests * update system test * address comments * 🦉 Updates from OwlBot * revise logic for backwards compatibility * add tests * revise docstring * fix test * revise to DeprecationWarning * address comments and revise docstrings Co-authored-by: Tres Seaver <tseaver@palladion.com> Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: 3 people

google/cloud/storage/blob.py

@@ -3198,6 +3198,7 @@ def compose(
  timeout=_DEFAULT_TIMEOUT,
  if_generation_match=None,
  if_metageneration_match=None,
+ if_source_generation_match=None,
  retry=DEFAULT_RETRY_IF_GENERATION_SPECIFIED,
  ):
  """Concatenate source blobs into this one.
@@ -3218,73 +3219,98 @@ def compose(
  (Optional) The amount of time, in seconds, to wait
  for the server response. See: :ref:`configuring_timeouts`
 
- :type if_generation_match: list of long
+ :type if_generation_match: long
  :param if_generation_match:
- (Optional) Make the operation conditional on whether the blob's
- current generation matches the given value. Setting to 0 makes the
- operation succeed only if there are no live versions of the blob.
- The list must match ``sources`` item-to-item.
+ (Optional) Makes the operation conditional on whether the
+ destination object's current generation matches the given value.
+ Setting to 0 makes the operation succeed only if there are no live
+ versions of the object.
+
+ Note: In a previous version, this argument worked identically to the
+ ``if_source_generation_match`` argument. For backwards-compatibility reasons,
+ if a list is passed in, this argument will behave like ``if_source_generation_match``
+ and also issue a DeprecationWarning.
 
- :type if_metageneration_match: list of long
+ :type if_metageneration_match: long
  :param if_metageneration_match:
- (Optional) Make the operation conditional on whether the blob's
- current metageneration matches the given value. The list must match
- ``sources`` item-to-item.
+ (Optional) Makes the operation conditional on whether the
+ destination object's current metageneration matches the given
+ value.
+
+ If a list of long is passed in, no match operation will be performed.
+ (Deprecated: type(list of long) is supported for backwards-compatability reasons only.)
+
+ :type if_source_generation_match: list of long
+ :param if_source_generation_match:
+ (Optional) Makes the operation conditional on whether the current generation
+ of each source blob matches the corresponding generation.
+ The list must match ``sources`` item-to-item.
 
  :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
  :param retry:
  (Optional) How to retry the RPC. See: :ref:`configuring_retries`
 
  Example:
- Compose blobs using generation match preconditions.
+ Compose blobs using source generation match preconditions.
 
  >>> from google.cloud import storage
  >>> client = storage.Client()
  >>> bucket = client.bucket("bucket-name")
 
  >>> blobs = [bucket.blob("blob-name-1"), bucket.blob("blob-name-2")]
- >>> if_generation_match = [None] * len(blobs)
- >>> if_generation_match[0] = "123" # precondition for "blob-name-1"
+ >>> if_source_generation_match = [None] * len(blobs)
+ >>> if_source_generation_match[0] = "123" # precondition for "blob-name-1"
 
  >>> composed_blob = bucket.blob("composed-name")
- >>> composed_blob.compose(blobs, if_generation_match)
+ >>> composed_blob.compose(blobs, if_source_generation_match=if_source_generation_match)
  """
  sources_len = len(sources)
- if if_generation_match is not None and len(if_generation_match) != sources_len:
- raise ValueError(
- "'if_generation_match' length must be the same as 'sources' length"
+ client = self._require_client(client)
+ query_params = {}
+
+ if isinstance(if_generation_match, list):
+ warnings.warn(
+ "if_generation_match: type list is deprecated and supported for backwards-compatability reasons only."
+ "Use if_source_generation_match instead to match source objects generations.",
+ DeprecationWarning,
+ stacklevel=2,
  )
 
- if (
- if_metageneration_match is not None
- and len(if_metageneration_match) != sources_len
- ):
- raise ValueError(
- "'if_metageneration_match' length must be the same as 'sources' length"
+ if if_source_generation_match is not None:
+ raise ValueError(
+ "Use if_generation_match to match the generation of the destination object by passing in a generation number, instead of a list."
+ "Use if_source_generation_match to match source objects generations."
+ )
+
+ # if_generation_match: type list is deprecated. Instead use if_source_generation_match.
+ if_source_generation_match = if_generation_match
+ if_generation_match = None
+
+ if isinstance(if_metageneration_match, list):
+ warnings.warn(
+ "if_metageneration_match: type list is deprecated and supported for backwards-compatability reasons only."
+ "Note that the metageneration to be matched is that of the destination blob."
+ "Please pass in a single value (type long).",
+ DeprecationWarning,
+ stacklevel=2,
  )
 
- client = self._require_client(client)
- query_params = {}
+ if_metageneration_match = None
 
- if self.user_project is not None:
- query_params["userProject"] = self.user_project
+ if if_source_generation_match is None:
+ if_source_generation_match = [None] * sources_len
+ if len(if_source_generation_match) != sources_len:
+ raise ValueError(
+ "'if_source_generation_match' length must be the same as 'sources' length"
+ )
 
  source_objects = []
- for index, source in enumerate(sources):
- source_object = {"name": source.name}
+ for source, source_generation in zip(sources, if_source_generation_match):
+ source_object = {"name": source.name, "generation": source.generation}
 
  preconditions = {}
- if (
- if_generation_match is not None
- and if_generation_match[index] is not None
- ):
- preconditions["ifGenerationMatch"] = if_generation_match[index]
-
- if (
- if_metageneration_match is not None
- and if_metageneration_match[index] is not None
- ):
- preconditions["ifMetagenerationMatch"] = if_metageneration_match[index]
+ if source_generation is not None:
+ preconditions["ifGenerationMatch"] = source_generation
 
  if preconditions:
  source_object["objectPreconditions"] = preconditions
@@ -3295,6 +3321,16 @@ def compose(
  "sourceObjects": source_objects,
  "destination": self._properties.copy(),
  }
+
+ if self.user_project is not None:
+ query_params["userProject"] = self.user_project
+
+ _add_generation_match_parameters(
+ query_params,
+ if_generation_match=if_generation_match,
+ if_metageneration_match=if_metageneration_match,
+ )
+
  api_response = client._post_resource(
  "{}/compose".format(self.path),
  request,

tests/system/test_system.py

@@ -1723,7 +1723,7 @@ def test_compose_replace_existing_blob(self):
  composed = original.download_as_bytes()
  self.assertEqual(composed, BEFORE + TO_APPEND)
 
- def test_compose_with_generation_match(self):
+ def test_compose_with_generation_match_list(self):
  BEFORE = b"AAA\n"
  original = self.bucket.blob("original")
  original.content_type = "text/plain"
@@ -1751,6 +1751,49 @@ def test_compose_with_generation_match(self):
  composed = original.download_as_bytes()
  self.assertEqual(composed, BEFORE + TO_APPEND)
 
+ def test_compose_with_generation_match_long(self):
+ BEFORE = b"AAA\n"
+ original = self.bucket.blob("original")
+ original.content_type = "text/plain"
+ original.upload_from_string(BEFORE)
+ self.case_blobs_to_delete.append(original)
+
+ TO_APPEND = b"BBB\n"
+ to_append = self.bucket.blob("to_append")
+ to_append.upload_from_string(TO_APPEND)
+ self.case_blobs_to_delete.append(to_append)
+
+ with self.assertRaises(google.api_core.exceptions.PreconditionFailed):
+ original.compose([original, to_append], if_generation_match=0)
+
+ original.compose([original, to_append], if_generation_match=original.generation)
+
+ composed = original.download_as_bytes()
+ self.assertEqual(composed, BEFORE + TO_APPEND)
+
+ def test_compose_with_source_generation_match(self):
+ BEFORE = b"AAA\n"
+ original = self.bucket.blob("original")
+ original.content_type = "text/plain"
+ original.upload_from_string(BEFORE)
+ self.case_blobs_to_delete.append(original)
+
+ TO_APPEND = b"BBB\n"
+ to_append = self.bucket.blob("to_append")
+ to_append.upload_from_string(TO_APPEND)
+ self.case_blobs_to_delete.append(to_append)
+
+ with self.assertRaises(google.api_core.exceptions.PreconditionFailed):
+ original.compose([original, to_append], if_source_generation_match=[6, 7])
+
+ original.compose(
+ [original, to_append],
+ if_source_generation_match=[original.generation, to_append.generation],
+ )
+
+ composed = original.download_as_bytes()
+ self.assertEqual(composed, BEFORE + TO_APPEND)
+
  @unittest.skipUnless(USER_PROJECT, "USER_PROJECT not set in environment.")
  def test_compose_with_user_project(self):
  new_bucket_name = "compose-user-project" + unique_resource_id("-")