Add warning for users signing URLs without passing an explicit version.

storage/google/cloud/storage/blob.py

@@ -97,6 +97,12 @@
 _READ_LESS_THAN_SIZE = (
     "Size {:d} was specified but the file-like object only had " "{:d} bytes remaining."
 )
+_SIGNED_URL_V2_DEFAULT_MESSAGE = (
+    "You have generated a signed URL using the default v2 signing "
+    "implementation. In the future, this will default to v4. "
+    "You may experience breaking changes if you use longer than 7 day "
+    "expiration times with v4. To opt-in to the behavior specify version='v2'."
+)
 
 _DEFAULT_CHUNKSIZE = 104857600  # 1024 * 1024 B * 100 = 100 MB
 _MAX_MULTIPART_SIZE = 8388608  # 8 MB
@@ -316,7 +322,7 @@ def generate_signed_url(
         query_parameters=None,
         client=None,
         credentials=None,
-        version="v2",
+        version=None,
     ):
         """Generates a signed URL for this blob.
 
@@ -421,7 +427,10 @@ def generate_signed_url(
         :returns: A signed URL you can use to access the resource
                   until expiration.
         """
-        if version not in ("v2", "v4"):
+        if version is None:
+            version = "v2"
+            warnings.warn(DeprecationWarning(_SIGNED_URL_V2_DEFAULT_MESSAGE))
+        elif version not in ("v2", "v4"):
             raise ValueError("'version' must be either 'v2' or 'v4'")
 
         resource = "/{bucket_name}/{quoted_name}".format(

storage/google/cloud/storage/bucket.py

@@ -37,6 +37,7 @@
 from google.cloud.storage._signing import generate_signed_url_v4
 from google.cloud.storage.acl import BucketACL
 from google.cloud.storage.acl import DefaultObjectACL
+from google.cloud.storage.blob import _SIGNED_URL_V2_DEFAULT_MESSAGE
 from google.cloud.storage.blob import Blob
 from google.cloud.storage.notification import BucketNotification
 from google.cloud.storage.notification import NONE_PAYLOAD_FORMAT
@@ -1983,7 +1984,7 @@ def generate_signed_url(
         query_parameters=None,
         client=None,
         credentials=None,
-        version="v2",
+        version=None,
     ):
         """Generates a signed URL for this bucket.
 
@@ -2063,7 +2064,10 @@ def generate_signed_url(
         :returns: A signed URL you can use to access the resource
                   until expiration.
         """
-        if version not in ("v2", "v4"):
+        if version is None:
+            version = "v2"
+            warnings.warn(DeprecationWarning(_SIGNED_URL_V2_DEFAULT_MESSAGE))
+        elif version not in ("v2", "v4"):
             raise ValueError("'version' must be either 'v2' or 'v4'")
 
         resource = "/{bucket_name}".format(bucket_name=self.name)

storage/tests/unit/test_blob.py

@@ -20,6 +20,7 @@
 import os
 import tempfile
 import unittest
+import warnings
 
 import google.cloud.storage.blob
 import mock
@@ -363,7 +364,7 @@ def test_generate_signed_url_w_invalid_version(self):
 
     def _generate_signed_url_helper(
         self,
-        version,
+        version=None,
         blob_name="blob-name",
         api_access_endpoint=None,
         method="GET",
@@ -393,24 +394,38 @@ def _generate_signed_url_helper(
         client = _Client(connection)
         bucket = _Bucket(client)
         blob = self._make_one(blob_name, bucket=bucket)
-        to_patch = "google.cloud.storage.blob.generate_signed_url_{}".format(version)
+
+        if version is None:
+            effective_version = "v2"
+        else:
+            effective_version = version
+
+        to_patch = "google.cloud.storage.blob.generate_signed_url_{}".format(
+            effective_version)
 
         with mock.patch(to_patch) as signer:
-            signed_uri = blob.generate_signed_url(
-                expiration=expiration,
-                max_age=max_age,
-                api_access_endpoint=api_access_endpoint,
-                method=method,
-                credentials=credentials,
-                content_md5=content_md5,
-                content_type=content_type,
-                response_type=response_type,
-                response_disposition=response_disposition,
-                generation=generation,
-                headers=headers,
-                query_parameters=query_parameters,
-                version=version,
-            )
+            with warnings.catch_warnings(record=True) as warned:
+                signed_uri = blob.generate_signed_url(
+                    expiration=expiration,
+                    max_age=max_age,
+                    api_access_endpoint=api_access_endpoint,
+                    method=method,
+                    credentials=credentials,
+                    content_md5=content_md5,
+                    content_type=content_type,
+                    response_type=response_type,
+                    response_disposition=response_disposition,
+                    generation=generation,
+                    headers=headers,
+                    query_parameters=query_parameters,
+                    version=version,
+                )
+
+        if version is None:
+            self.assertEqual(len(warned), 1)
+            self.assertIs(warned[0].category, DeprecationWarning)
+        else:
+            self.assertEqual(len(warned), 0)
 
         self.assertEqual(signed_uri, signer.return_value)
 
@@ -437,6 +452,9 @@ def _generate_signed_url_helper(
         }
         signer.assert_called_once_with(expected_creds, **expected_kwargs)
 
+    def test_generate_signed_url_no_version_passed_warning(self):
+        self._generate_signed_url_helper()
+
     def _generate_signed_url_v2_helper(self, **kw):
         version = "v2"
         self._generate_signed_url_helper(version, **kw)

storage/tests/unit/test_bucket.py

@@ -14,6 +14,7 @@
 
 import datetime
 import unittest
+import warnings
 
 import mock
 
@@ -2583,7 +2584,7 @@ def test_generate_signed_url_w_invalid_version(self):
 
     def _generate_signed_url_helper(
         self,
-        version,
+        version=None,
         bucket_name="bucket-name",
         api_access_endpoint=None,
         method="GET",
@@ -2612,19 +2613,33 @@ def _generate_signed_url_helper(
         connection = _Connection()
         client = _Client(connection)
         bucket = self._make_one(name=bucket_name, client=client)
-        to_patch = "google.cloud.storage.bucket.generate_signed_url_{}".format(version)
+
+        if version is None:
+            effective_version = "v2"
+        else:
+            effective_version = version
+
+        to_patch = "google.cloud.storage.bucket.generate_signed_url_{}".format(
+            effective_version)
 
         with mock.patch(to_patch) as signer:
-            signed_uri = bucket.generate_signed_url(
-                expiration=expiration,
-                max_age=max_age,
-                api_access_endpoint=api_access_endpoint,
-                method=method,
-                credentials=credentials,
-                headers=headers,
-                query_parameters=query_parameters,
-                version=version,
-            )
+            with warnings.catch_warnings(record=True) as warned:
+                signed_uri = bucket.generate_signed_url(
+                    expiration=expiration,
+                    max_age=max_age,
+                    api_access_endpoint=api_access_endpoint,
+                    method=method,
+                    credentials=credentials,
+                    headers=headers,
+                    query_parameters=query_parameters,
+                    version=version,
+                )
+
+        if version is None:
+            self.assertEqual(len(warned), 1)
+            self.assertIs(warned[0].category, DeprecationWarning)
+        else:
+            self.assertEqual(len(warned), 0)
 
         self.assertEqual(signed_uri, signer.return_value)
 
@@ -2646,6 +2661,9 @@ def _generate_signed_url_helper(
         }
         signer.assert_called_once_with(expected_creds, **expected_kwargs)
 
+    def test_generate_signed_url_no_version_passed_warning(self):
+        self._generate_signed_url_helper()
+
     def _generate_signed_url_v2_helper(self, **kw):
         version = "v2"
         self._generate_signed_url_helper(version, **kw)