feat: add if*generation*match args into Bucket.delete_blobs()

google/cloud/storage/bucket.py

@@ -1455,7 +1455,17 @@ def delete_blob(
             timeout=timeout,
         )
 
-    def delete_blobs(self, blobs, on_error=None, client=None, timeout=_DEFAULT_TIMEOUT):
+    def delete_blobs(
+        self,
+        blobs,
+        on_error=None,
+        client=None,
+        timeout=_DEFAULT_TIMEOUT,
+        if_generation_match=None,
+        if_generation_not_match=None,
+        if_metageneration_match=None,
+        if_metageneration_not_match=None,
+    ):
         """Deletes a list of blobs from the current bucket.
 
         Uses :meth:`delete_blob` to delete each individual blob.
@@ -1484,15 +1494,74 @@ def delete_blobs(self, blobs, on_error=None, client=None, timeout=_DEFAULT_TIMEO
             Can also be passed as a tuple (connect_timeout, read_timeout).
             See :meth:`requests.Session.request` documentation for details.
 
+        :type if_generation_match: list of 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
+                                    ``blobs`` item-to-item.
+
+        :type if_generation_not_match: list of long
+        :param if_generation_not_match: (Optional) Make the operation conditional on whether
+                                        the blob's current generation does not match the given
+                                        value. If no live blob exists, the precondition fails.
+                                        Setting to 0 makes the operation succeed only if there
+                                        is a live version of the blob. The list must match
+                                        ``blobs`` item-to-item.
+
+        :type if_metageneration_match: list of 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 ``blobs`` item-to-item.
+
+        :type if_metageneration_not_match: list of long
+        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
+                                            blob's current metageneration does not match the given value.
+                                            The list must match ``blobs`` item-to-item.
+
         :raises: :class:`~google.cloud.exceptions.NotFound` (if
                  `on_error` is not passed).
+
+        Example:
+            Delete blobs using 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"
+
+            >>> bucket.delete_blobs(blobs, if_generation_match=if_generation_match)
         """
+        _raise_if_len_differs(
+            len(blobs),
+            if_generation_match=if_generation_match,
+            if_generation_not_match=if_generation_not_match,
+            if_metageneration_match=if_metageneration_match,
+            if_metageneration_not_match=if_metageneration_not_match,
+        )
+        if_generation_match = iter(if_generation_match or [])
+        if_generation_not_match = iter(if_generation_not_match or [])
+        if_metageneration_match = iter(if_metageneration_match or [])
+        if_metageneration_not_match = iter(if_metageneration_not_match or [])
+
         for blob in blobs:
             try:
                 blob_name = blob
                 if not isinstance(blob_name, six.string_types):
                     blob_name = blob.name
-                self.delete_blob(blob_name, client=client, timeout=timeout)
+                self.delete_blob(
+                    blob_name,
+                    client=client,
+                    timeout=timeout,
+                    if_generation_match=next(if_generation_match, None),
+                    if_generation_not_match=next(if_generation_not_match, None),
+                    if_metageneration_match=next(if_metageneration_match, None),
+                    if_metageneration_not_match=next(if_metageneration_not_match, None),
+                )
             except NotFound:
                 if on_error is not None:
                     on_error(blob)
@@ -2980,3 +3049,23 @@ def generate_signed_url(
             headers=headers,
             query_parameters=query_parameters,
         )
+
+
+def _raise_if_len_differs(expected_len, **generation_match_args):
+    """
+    Raise an error if any generation match argument
+    is set and its len differs from the given value.
+
+    :type expected_len: int
+    :param expected_len: Expected argument length in case it's set.
+
+    :type generation_match_args: dict
+    :param generation_match_args: Lists, which length must be checked.
+
+    :raises: :exc:`ValueError` if any argument set, but has an unexpected length.
+    """
+    for name, value in generation_match_args.items():
+        if value is not None and len(value) != expected_len:
+            raise ValueError(
+                "'{}' length must be the same as 'blobs' length".format(name)
+            )

tests/unit/test_bucket.py

@@ -1146,6 +1146,82 @@ def test_delete_blobs_hit_w_user_project(self):
         self.assertEqual(kw[0]["query_params"], {"userProject": USER_PROJECT})
         self.assertEqual(kw[0]["timeout"], 42)
 
+    def test_delete_blobs_w_generation_match(self):
+        NAME = "name"
+        BLOB_NAME = "blob-name"
+        BLOB_NAME2 = "blob-name2"
+        GENERATION_NUMBER = 6
+        GENERATION_NUMBER2 = 9
+
+        connection = _Connection({}, {})
+        client = _Client(connection)
+        bucket = self._make_one(client=client, name=NAME)
+        bucket.delete_blobs(
+            [BLOB_NAME, BLOB_NAME2],
+            timeout=42,
+            if_generation_match=[GENERATION_NUMBER, GENERATION_NUMBER2],
+        )
+        kw = connection._requested
+        self.assertEqual(len(kw), 2)
+
+        self.assertEqual(kw[0]["method"], "DELETE")
+        self.assertEqual(kw[0]["path"], "/b/%s/o/%s" % (NAME, BLOB_NAME))
+        self.assertEqual(kw[0]["timeout"], 42)
+        self.assertEqual(
+            kw[0]["query_params"], {"ifGenerationMatch": GENERATION_NUMBER}
+        )
+        self.assertEqual(kw[1]["method"], "DELETE")
+        self.assertEqual(kw[1]["path"], "/b/%s/o/%s" % (NAME, BLOB_NAME2))
+        self.assertEqual(kw[1]["timeout"], 42)
+        self.assertEqual(
+            kw[1]["query_params"], {"ifGenerationMatch": GENERATION_NUMBER2}
+        )
+
+    def test_delete_blobs_w_generation_match_wrong_len(self):
+        NAME = "name"
+        BLOB_NAME = "blob-name"
+        BLOB_NAME2 = "blob-name2"
+        GENERATION_NUMBER = 6
+
+        connection = _Connection()
+        client = _Client(connection)
+        bucket = self._make_one(client=client, name=NAME)
+        with self.assertRaises(ValueError):
+            bucket.delete_blobs(
+                [BLOB_NAME, BLOB_NAME2],
+                timeout=42,
+                if_generation_not_match=[GENERATION_NUMBER],
+            )
+
+    def test_delete_blobs_w_generation_match_none(self):
+        NAME = "name"
+        BLOB_NAME = "blob-name"
+        BLOB_NAME2 = "blob-name2"
+        GENERATION_NUMBER = 6
+        GENERATION_NUMBER2 = None
+
+        connection = _Connection({}, {})
+        client = _Client(connection)
+        bucket = self._make_one(client=client, name=NAME)
+        bucket.delete_blobs(
+            [BLOB_NAME, BLOB_NAME2],
+            timeout=42,
+            if_generation_match=[GENERATION_NUMBER, GENERATION_NUMBER2],
+        )
+        kw = connection._requested
+        self.assertEqual(len(kw), 2)
+
+        self.assertEqual(kw[0]["method"], "DELETE")
+        self.assertEqual(kw[0]["path"], "/b/%s/o/%s" % (NAME, BLOB_NAME))
+        self.assertEqual(kw[0]["timeout"], 42)
+        self.assertEqual(
+            kw[0]["query_params"], {"ifGenerationMatch": GENERATION_NUMBER}
+        )
+        self.assertEqual(kw[1]["method"], "DELETE")
+        self.assertEqual(kw[1]["path"], "/b/%s/o/%s" % (NAME, BLOB_NAME2))
+        self.assertEqual(kw[1]["timeout"], 42)
+        self.assertEqual(kw[1]["query_params"], {})
+
     def test_delete_blobs_miss_no_on_error(self):
         from google.cloud.exceptions import NotFound