S3:CompleteMultipartUpload - error on empty part list

moto/s3/models.py

@@ -365,6 +365,9 @@ class FakeMultipart(BaseModel):
             last = part
             count += 1
 
+        if count == 0:
+            raise MalformedXML
+
         etag = hashlib.md5()
         etag.update(bytes(md5s))
         return total, "{0}-{1}".format(etag.hexdigest(), count)

tests/terraform-tests.failures.txt

@@ -8,5 +8,4 @@ TestAccAWSDefaultSecurityGroup_Classic_
 TestAccDataSourceAwsNetworkInterface_CarrierIPAssociation
 TestAccAWSRouteTable_IPv4_To_LocalGateway
 TestAccAWSRouteTable_IPv4_To_VpcEndpoint
-TestAccAWSRouteTable_VpcClassicLink
+TestAccAWSRouteTable_VpcClassicLink
-TestAccAWSS3BucketObject_updatesWithVersioningViaAccessPoint

tests/terraform-tests.success.txt

@@ -120,9 +120,7 @@ TestAccAWSENI_Tags
 TestAccAWSENI_basic
 TestAccAWSENI_IPv6
 TestAccAWSENI_disappears
-TestAccAWSS3BucketObject
 TestAccAWSS3BucketPolicy
-TestAccAWSS3AccessPoint
 TestAccAWSS3BucketPublicAccessBlock
 TestAccAWSS3ObjectCopy
 TestAccAWSIAMPolicy_

tests/test_s3/test_s3_multipart.py

@@ -1,14 +1,14 @@
+import boto3
 import os
 import pytest
+import sure  # noqa # pylint: disable=unused-import
+
+from botocore.client import ClientError
 from functools import wraps
 from io import BytesIO
 
-import boto3
-from botocore.client import ClientError
-
 from moto.s3.responses import DEFAULT_REGION_NAME
 
-import sure  # noqa # pylint: disable=unused-import
 
 from moto import settings, mock_s3
 import moto.s3.models as s3model
@@ -839,3 +839,30 @@ def test_multipart_part_size():
     for i in range(1, n_parts + 1):
         obj = s3.head_object(Bucket="mybucket", Key="the-key", PartNumber=i)
         assert obj["ContentLength"] == REDUCED_PART_SIZE + i
+
+
+@mock_s3
+def test_complete_multipart_with_empty_partlist():
+    """
+    When completing a MultipartUpload with an empty part list, AWS responds with an InvalidXML-error
+
+    Verify that we send the same error, to duplicate boto3's behaviour
+    """
+    bucket = "testbucketthatcompletesmultipartuploadwithoutparts"
+    key = "test-multi-empty"
+
+    client = boto3.client("s3", region_name=DEFAULT_REGION_NAME)
+    client.create_bucket(Bucket=bucket)
+
+    response = client.create_multipart_upload(Bucket=bucket, Key=key,)
+    uid = response["UploadId"]
+
+    upload = boto3.resource("s3").MultipartUpload(bucket, key, uid)
+
+    with pytest.raises(ClientError) as exc:
+        upload.complete(MultipartUpload={"Parts": []})
+    err = exc.value.response["Error"]
+    err["Code"].should.equal("MalformedXML")
+    err["Message"].should.equal(
+        "The XML you provided was not well-formed or did not validate against our published schema"
+    )