Repository: googleapis/python-storage

Issue:
Policy V4 returns non utf8 decoded strings
We received a PR to update our Python Sample for Policy V4. The resulting string should provide a UTF-8 decoded value for all fields. 

Right now a user must decode it manually which isn't helpful.

Example:
```python
def generate_signed_post_policy_v4(bucket_name, blob_name):
    """Generates a v4 POST Policy and prints an HTML form."""
    # bucket_name = 'your-bucket-name'
    # blob_name = 'your-object-name'

    storage_client = storage.Client()

    policy = storage_client.generate_signed_post_policy_v4(
        bucket_name,
        blob_name,
        expiration=datetime.timedelta(minutes=10),
        fields={
          'x-goog-meta-test': 'data'
        }
    )

    # Create an HTML form with the provided policy
    header = "<form action='{}' method='POST' enctype='multipart/form-data'>\n"
    form = header.format(policy["url"])

    # Include all fields returned in the HTML form as they're required
    for key, value in policy["fields"].items():
        if type(value) == bytes: # <-- offending code
            value = value.decode("utf-8")
        form += "  <input name='{}' value='{}' type='hidden'/>\n".format(key, value)

    form += "  <input type='file' name='file'/><br />\n"
    form += "  <input type='submit' value='Upload File' /><br />\n"
    form += "</form>"

    print(form)

    return form
```

Request is to update Python implementation to return decoded string to the end-user.



Discussion:

Patch:
diff --git a/google/cloud/storage/client.py b/google/cloud/storage/client.py
index fd29abe..e522052 100644
--- a/google/cloud/storage/client.py
+++ b/google/cloud/storage/client.py
@@ -1090,7 +1090,7 @@ class Client(ClientWithProject):
                 "x-goog-credential": x_goog_credential,
                 "x-goog-date": timestamp,
                 "x-goog-signature": signature,
-                "policy": str_to_sign,
+                "policy": str_to_sign.decode("utf-8"),
             }
         )
         # designate URL


Test patch:
diff --git a/tests/unit/test_client.py b/tests/unit/test_client.py
index 600e119..e423210 100644
--- a/tests/unit/test_client.py
+++ b/tests/unit/test_client.py
@@ -1606,7 +1606,7 @@ class TestClient(unittest.TestCase):
         BUCKET_NAME = "bucket-name"
         BLOB_NAME = "object-name"
         EXPECTED_SIGN = "5369676e61747572655f6279746573"
-        EXPECTED_POLICY = b"eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiYnVja2V0IjoiYnVja2V0LW5hbWUifSx7ImtleSI6Im9iamVjdC1uYW1lIn0seyJ4LWdvb2ctZGF0ZSI6IjIwMjAwMzEyVDExNDcxNloifSx7IngtZ29vZy1jcmVkZW50aWFsIjoidGVzdEBtYWlsLmNvbS8yMDIwMDMxMi9hdXRvL3N0b3JhZ2UvZ29vZzRfcmVxdWVzdCJ9LHsieC1nb29nLWFsZ29yaXRobSI6IkdPT0c0LVJTQS1TSEEyNTYifV0sImV4cGlyYXRpb24iOiIyMDIwLTAzLTI2VDAwOjAwOjEwWiJ9"
+        EXPECTED_POLICY = "eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiYnVja2V0IjoiYnVja2V0LW5hbWUifSx7ImtleSI6Im9iamVjdC1uYW1lIn0seyJ4LWdvb2ctZGF0ZSI6IjIwMjAwMzEyVDExNDcxNloifSx7IngtZ29vZy1jcmVkZW50aWFsIjoidGVzdEBtYWlsLmNvbS8yMDIwMDMxMi9hdXRvL3N0b3JhZ2UvZ29vZzRfcmVxdWVzdCJ9LHsieC1nb29nLWFsZ29yaXRobSI6IkdPT0c0LVJTQS1TSEEyNTYifV0sImV4cGlyYXRpb24iOiIyMDIwLTAzLTI2VDAwOjAwOjEwWiJ9"
 
         client = self._make_one(project="PROJECT")
 
@@ -1644,7 +1644,7 @@ class TestClient(unittest.TestCase):
         BUCKET_NAME = "bucket-name"
         BLOB_NAME = "object-name"
         EXPECTED_SIGN = "5369676e61747572655f6279746573"
-        EXPECTED_POLICY = b"eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiYnVja2V0IjoiYnVja2V0LW5hbWUifSx7ImtleSI6Im9iamVjdC1uYW1lIn0seyJ4LWdvb2ctZGF0ZSI6IjIwMjAwMzEyVDExNDcxNloifSx7IngtZ29vZy1jcmVkZW50aWFsIjoidGVzdEBtYWlsLmNvbS8yMDIwMDMxMi9hdXRvL3N0b3JhZ2UvZ29vZzRfcmVxdWVzdCJ9LHsieC1nb29nLWFsZ29yaXRobSI6IkdPT0c0LVJTQS1TSEEyNTYifV0sImV4cGlyYXRpb24iOiIyMDIwLTAzLTI2VDAwOjAwOjEwWiJ9"
+        EXPECTED_POLICY = "eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiYnVja2V0IjoiYnVja2V0LW5hbWUifSx7ImtleSI6Im9iamVjdC1uYW1lIn0seyJ4LWdvb2ctZGF0ZSI6IjIwMjAwMzEyVDExNDcxNloifSx7IngtZ29vZy1jcmVkZW50aWFsIjoidGVzdEBtYWlsLmNvbS8yMDIwMDMxMi9hdXRvL3N0b3JhZ2UvZ29vZzRfcmVxdWVzdCJ9LHsieC1nb29nLWFsZ29yaXRobSI6IkdPT0c0LVJTQS1TSEEyNTYifV0sImV4cGlyYXRpb24iOiIyMDIwLTAzLTI2VDAwOjAwOjEwWiJ9"
 
         client = self._make_one(
             project="PROJECT", credentials=_create_signing_credentials()
@@ -1684,7 +1684,7 @@ class TestClient(unittest.TestCase):
         BLOB_NAME = "object-name"
         FIELD1_VALUE = "Value1"
         EXPECTED_SIGN = "5369676e61747572655f6279746573"
-        EXPECTED_POLICY = b"eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiZmllbGQxIjoiVmFsdWUxIn0seyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsia2V5Ijoib2JqZWN0LW5hbWUifSx7IngtZ29vZy1kYXRlIjoiMjAyMDAzMTJUMTE0NzE2WiJ9LHsieC1nb29nLWNyZWRlbnRpYWwiOiJ0ZXN0QG1haWwuY29tLzIwMjAwMzEyL2F1dG8vc3RvcmFnZS9nb29nNF9yZXF1ZXN0In0seyJ4LWdvb2ctYWxnb3JpdGhtIjoiR09PRzQtUlNBLVNIQTI1NiJ9XSwiZXhwaXJhdGlvbiI6IjIwMjAtMDMtMjZUMDA6MDA6MTBaIn0="
+        EXPECTED_POLICY = "eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiZmllbGQxIjoiVmFsdWUxIn0seyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsia2V5Ijoib2JqZWN0LW5hbWUifSx7IngtZ29vZy1kYXRlIjoiMjAyMDAzMTJUMTE0NzE2WiJ9LHsieC1nb29nLWNyZWRlbnRpYWwiOiJ0ZXN0QG1haWwuY29tLzIwMjAwMzEyL2F1dG8vc3RvcmFnZS9nb29nNF9yZXF1ZXN0In0seyJ4LWdvb2ctYWxnb3JpdGhtIjoiR09PRzQtUlNBLVNIQTI1NiJ9XSwiZXhwaXJhdGlvbiI6IjIwMjAtMDMtMjZUMDA6MDA6MTBaIn0="
 
         client = self._make_one(project="PROJECT")
 
@@ -1774,7 +1774,7 @@ class TestClient(unittest.TestCase):
 
     def test_get_signed_policy_v4_no_expiration(self):
         BUCKET_NAME = "bucket-name"
-        EXPECTED_POLICY = b"eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsia2V5Ijoib2JqZWN0LW5hbWUifSx7IngtZ29vZy1kYXRlIjoiMjAyMDAzMTJUMTE0NzE2WiJ9LHsieC1nb29nLWNyZWRlbnRpYWwiOiJ0ZXN0QG1haWwuY29tLzIwMjAwMzEyL2F1dG8vc3RvcmFnZS9nb29nNF9yZXF1ZXN0In0seyJ4LWdvb2ctYWxnb3JpdGhtIjoiR09PRzQtUlNBLVNIQTI1NiJ9XSwiZXhwaXJhdGlvbiI6IjIwMjAtMDMtMjZUMDA6MDA6MTBaIn0="
+        EXPECTED_POLICY = "eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsia2V5Ijoib2JqZWN0LW5hbWUifSx7IngtZ29vZy1kYXRlIjoiMjAyMDAzMTJUMTE0NzE2WiJ9LHsieC1nb29nLWNyZWRlbnRpYWwiOiJ0ZXN0QG1haWwuY29tLzIwMjAwMzEyL2F1dG8vc3RvcmFnZS9nb29nNF9yZXF1ZXN0In0seyJ4LWdvb2ctYWxnb3JpdGhtIjoiR09PRzQtUlNBLVNIQTI1NiJ9XSwiZXhwaXJhdGlvbiI6IjIwMjAtMDMtMjZUMDA6MDA6MTBaIn0="
 
         client = self._make_one(project="PROJECT")
 
@@ -1798,7 +1798,7 @@ class TestClient(unittest.TestCase):
         BUCKET_NAME = "bucket-name"
         BLOB_NAME = "object-name"
         EXPECTED_SIGN = "0c4003044105"
-        EXPECTED_POLICY = b"eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiYnVja2V0IjoiYnVja2V0LW5hbWUifSx7ImtleSI6Im9iamVjdC1uYW1lIn0seyJ4LWdvb2ctZGF0ZSI6IjIwMjAwMzEyVDExNDcxNloifSx7IngtZ29vZy1jcmVkZW50aWFsIjoidGVzdEBtYWlsLmNvbS8yMDIwMDMxMi9hdXRvL3N0b3JhZ2UvZ29vZzRfcmVxdWVzdCJ9LHsieC1nb29nLWFsZ29yaXRobSI6IkdPT0c0LVJTQS1TSEEyNTYifV0sImV4cGlyYXRpb24iOiIyMDIwLTAzLTI2VDAwOjAwOjEwWiJ9"
+        EXPECTED_POLICY = "eyJjb25kaXRpb25zIjpbeyJidWNrZXQiOiJidWNrZXQtbmFtZSJ9LHsiYWNsIjoicHJpdmF0ZSJ9LFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwidGV4dC9wbGFpbiJdLHsiYnVja2V0IjoiYnVja2V0LW5hbWUifSx7ImtleSI6Im9iamVjdC1uYW1lIn0seyJ4LWdvb2ctZGF0ZSI6IjIwMjAwMzEyVDExNDcxNloifSx7IngtZ29vZy1jcmVkZW50aWFsIjoidGVzdEBtYWlsLmNvbS8yMDIwMDMxMi9hdXRvL3N0b3JhZ2UvZ29vZzRfcmVxdWVzdCJ9LHsieC1nb29nLWFsZ29yaXRobSI6IkdPT0c0LVJTQS1TSEEyNTYifV0sImV4cGlyYXRpb24iOiIyMDIwLTAzLTI2VDAwOjAwOjEwWiJ9"
 
         client = self._make_one(project="PROJECT")