pythonic way to construct form-data and address review comments

docs/API.md

@@ -1436,11 +1436,13 @@ __Example__
 
 ```py
 policy = PostPolicy(
-    "bucket_name", datetime.utcnow() + timedelta(days=10),
+    "my-bucket", datetime.utcnow() + timedelta(days=10),
 )
-policy.add_starts_with_condition("key", "objectPrefix/")
-form_data = presigned_post_policy(policy)
-print(form_data)
+policy.add_starts_with_condition("key", "my/object/prefix/")
+policy.add_content_length_range_condition(
+    1*1024*1024, 10*1024*1024,
+)
+form_data = client.presigned_post_policy(policy)
 ```
 
 ## 5. Explore Further

examples/presigned_post_policy.py

@@ -14,10 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Note: my-bucketname, my-objectname, YOUR-ACCESSKEYID, and
-# YOUR-SECRETACCESSKEY are dummy values, please replace them with original
-# values.
-
 from datetime import datetime, timedelta
 
 from minio import Minio
@@ -30,16 +26,16 @@
 )
 
 policy = PostPolicy(
-    "bucket_name", datetime.utcnow() + timedelta(days=10),
+    "my-bucket", datetime.utcnow() + timedelta(days=10),
 )
-policy.add_starts_with_condition("key", "objectPrefix/")
+policy.add_starts_with_condition("key", "my/object/prefix/")
 policy.add_content_length_range_condition(1*1024*1024, 10*1024*1024)
 
 form_data = client.presigned_post_policy(policy)
 
 curl_cmd = (
     "curl -X POST "
-    "https://s3.amazonaws.com/bucket_name "
+    "https://s3.amazonaws.com/my-bucket "
     "{0} -F file=@<FILE>"
 ).format(
     " ".join(["-F {0}={1}".format(k, v) for k, v in form_data.items()]),

minio/api.py

@@ -1772,11 +1772,13 @@ def presigned_post_policy(self, policy):
 
         Example::
             policy = PostPolicy(
-                "bucket_name", datetime.utcnow() + timedelta(days=10),
+                "my-bucket", datetime.utcnow() + timedelta(days=10),
             )
-            policy.add_starts_with_condition("key", "objectPrefix/")
-            form_data = presigned_post_policy(policy)
-            print(form_data)
+            policy.add_starts_with_condition("key", "my/object/prefix/")
+            policy.add_content_length_range_condition(
+                1*1024*1024, 10*1024*1024,
+            )
+            form_data = client.presigned_post_policy(policy)
         """
         if not isinstance(policy, PostPolicy):
             raise ValueError("policy must be PostPolicy type")

minio/datatypes.py

@@ -22,6 +22,7 @@
 
 import base64
 import datetime
+import json
 from collections import OrderedDict
 from urllib.parse import unquote
 from xml.etree import ElementTree as ET
@@ -574,25 +575,10 @@ def uploads(self):
 
 
 def _trim_dollar(value):
-    """Trime dollar character if present."""
+    """Trim dollar character if present."""
     return value[1:] if value.startswith("$") else value
 
 
-def _quote(value):
-    """Quote value."""
-    return '"{0}"'.format(value)
-
-
-def _get_condition(condition, element, value, is_end=False):
-    """Get condition string."""
-    return "    [{0}, {1}, {2}]{3}".format(
-        _quote(condition),
-        _quote("$" + element),
-        _quote(value),
-        "" if is_end else ",",
-    )
-
-
 class PostPolicy:
     """
     Post policy information to be used to generate presigned post policy
@@ -698,42 +684,28 @@ def form_data(self, creds, region):
         ):
             raise ValueError("key condition must be set")
 
-        data = ["{"]
-        data.append(
-            "  {0}: {1},".format(
-                _quote("expiration"),
-                _quote(to_iso8601utc(self._expiration)),
-            ),
-        )
-        data.append('  "conditions": [')
-        data.append(_get_condition(_EQ, "bucket", self._bucket_name))
+        policy = OrderedDict()
+        policy["expiration"] = to_iso8601utc(self._expiration)
+        policy["conditions"] = [[_EQ, "$bucket", self._bucket_name]]
         for cond_key, conditions in self._conditions.items():
             for key, value in conditions.items():
-                data.append(_get_condition(cond_key, key, value))
+                policy["conditions"].append([cond_key, "$"+key, value])
         if self._lower_limit is not None and self._upper_limit is not None:
-            data.append(
-                '    ["content-length-range", {0}, {1}],'.format(
-                    self._lower_limit, self._upper_limit,
-                ),
+            policy["conditions"].append(
+                ["content-length-range", self._lower_limit, self._upper_limit],
             )
-
         utcnow = datetime.datetime.utcnow()
         credential = get_credential_string(creds.access_key, utcnow, region)
         amz_date = to_amz_date(utcnow)
-
-        data.append(_get_condition("eq", "x-amz-algorithm", _ALGORITHM))
-        data.append(_get_condition("eq", "x-amz-credential", credential))
+        policy["conditions"].append([_EQ, "$x-amz-algorithm", _ALGORITHM])
+        policy["conditions"].append([_EQ, "$x-amz-credential", credential])
         if creds.session_token:
-            data.append(
-                _get_condition(
-                    "eq", "x-amz-security-token", creds.session_token,
-                ),
+            policy["conditions"].append(
+                [_EQ, "$x-amz-security-token", creds.session_token],
             )
-        data.append(_get_condition("eq", "x-amz-date", amz_date, True))
-        data.append("  ]")
-        data.append("}")
+        policy["conditions"].append([_EQ, "$x-amz-date", amz_date])
 
-        policy = base64.b64encode("\n".join(data).encode())
+        policy = base64.b64encode(json.dumps(policy).encode())
         signature = post_presign_v4(
             policy.decode(), creds.secret_key, utcnow, region,
         )

tests/functional/tests.py

@@ -1550,16 +1550,18 @@ def test_presigned_post_policy(log_entry):
         no_of_days = 10
         prefix = 'objectPrefix/'
 
-        # Post policy.
         policy = PostPolicy(
             bucket_name, datetime.utcnow() + timedelta(days=no_of_days),
         )
         policy.add_starts_with_condition("key", prefix)
-        # post_policy arg is a class. To avoid displaying meaningless value
-        # for the class, policy settings are made part of the args for
-        # clarity and debugging purposes.
-        log_entry["args"]["post_policy"] = {'prefix': prefix,
-                                            'expires_in_days': no_of_days}
+        policy.add_content_length_range_condition(64*KB, 10*MB)
+        policy.add_starts_with_condition("Content-Type", "image/")
+        log_entry["args"]["post_policy"] = {
+            "prefix": prefix,
+            "expires_in_days": no_of_days,
+            "content_length_range": "64KiB to 10MiB",
+            "Content-Type": "image/",
+        }
         _CLIENT.presigned_post_policy(policy)
     finally:
         _CLIENT.remove_bucket(bucket_name)