moto: s3: support partNumber for head_object

To support it, we need to keep multipart info in the key itself when
completing multipart upload.

Fixes #2154

Signed-off-by: Ruslan Kuprieiev <ruslan@iterative.ai>

moto/s3/models.py

@@ -52,8 +52,17 @@ class FakeDeleteMarker(BaseModel):
 
 class FakeKey(BaseModel):
 
-    def __init__(self, name, value, storage="STANDARD", etag=None, is_versioned=False, version_id=0,
-                 max_buffer_size=DEFAULT_KEY_BUFFER_SIZE):
+    def __init__(
+        self,
+        name,
+        value,
+        storage="STANDARD",
+        etag=None,
+        is_versioned=False,
+        version_id=0,
+        max_buffer_size=DEFAULT_KEY_BUFFER_SIZE,
+        multipart=None
+    ):
         self.name = name
         self.last_modified = datetime.datetime.utcnow()
         self.acl = get_canned_acl('private')
@@ -65,6 +74,7 @@ class FakeKey(BaseModel):
         self._version_id = version_id
         self._is_versioned = is_versioned
         self._tagging = FakeTagging()
+        self.multipart = multipart
 
         self._value_buffer = tempfile.SpooledTemporaryFile(max_size=max_buffer_size)
         self._max_buffer_size = max_buffer_size
@@ -782,7 +792,15 @@ class S3Backend(BaseBackend):
         bucket = self.get_bucket(bucket_name)
         return bucket.website_configuration
 
-    def set_key(self, bucket_name, key_name, value, storage=None, etag=None):
+    def set_key(
+        self,
+        bucket_name,
+        key_name,
+        value,
+        storage=None,
+        etag=None,
+        multipart=None,
+    ):
         key_name = clean_key_name(key_name)
         if storage is not None and storage not in STORAGE_CLASS:
             raise InvalidStorageClass(storage=storage)
@@ -795,7 +813,9 @@ class S3Backend(BaseBackend):
             storage=storage,
             etag=etag,
             is_versioned=bucket.is_versioned,
-            version_id=str(uuid.uuid4()) if bucket.is_versioned else None)
+            version_id=str(uuid.uuid4()) if bucket.is_versioned else None,
+            multipart=multipart,
+        )
 
         keys = [
             key for key in bucket.keys.getlist(key_name, [])
@@ -812,7 +832,7 @@ class S3Backend(BaseBackend):
         key.append_to_value(value)
         return key
 
-    def get_key(self, bucket_name, key_name, version_id=None):
+    def get_key(self, bucket_name, key_name, version_id=None, part_number=None):
         key_name = clean_key_name(key_name)
         bucket = self.get_bucket(bucket_name)
         key = None
@@ -827,6 +847,9 @@ class S3Backend(BaseBackend):
                         key = key_version
                         break
 
+            if part_number and key.multipart:
+                key = key.multipart.parts[part_number]
+
         if isinstance(key, FakeKey):
             return key
         else:
@@ -890,7 +913,12 @@ class S3Backend(BaseBackend):
             return
         del bucket.multiparts[multipart_id]
 
-        key = self.set_key(bucket_name, multipart.key_name, value, etag=etag)
+        key = self.set_key(
+            bucket_name,
+            multipart.key_name,
+            value, etag=etag,
+            multipart=multipart
+        )
         key.set_metadata(multipart.metadata)
         return key
 

moto/s3/responses.py

@@ -809,13 +809,20 @@ class ResponseObject(_TemplateEnvironmentMixin):
     def _key_response_head(self, bucket_name, query, key_name, headers):
         response_headers = {}
         version_id = query.get('versionId', [None])[0]
+        part_number = query.get('partNumber', [None])[0]
+        if part_number:
+            part_number = int(part_number)
 
         if_modified_since = headers.get('If-Modified-Since', None)
         if if_modified_since:
             if_modified_since = str_to_rfc_1123_datetime(if_modified_since)
 
         key = self.backend.get_key(
-            bucket_name, key_name, version_id=version_id)
+            bucket_name,
+            key_name,
+            version_id=version_id,
+            part_number=part_number
+        )
         if key:
             response_headers.update(key.metadata)
             response_headers.update(key.response_dict)

tests/test_s3/test_s3.py

@@ -1671,6 +1671,42 @@ def test_boto3_multipart_etag():
     resp['ETag'].should.equal(EXPECTED_ETAG)
 
 
+@mock_s3
+@reduced_min_part_size
+def test_boto3_multipart_part_size():
+    s3 = boto3.client('s3', region_name='us-east-1')
+    s3.create_bucket(Bucket='mybucket')
+
+    mpu = s3.create_multipart_upload(Bucket='mybucket', Key='the-key')
+    mpu_id = mpu["UploadId"]
+
+    parts = []
+    n_parts = 10
+    for i in range(1, n_parts + 1):
+        part_size = 5 * 1024 * 1024
+        body = b'1' * part_size
+        part = s3.upload_part(
+            Bucket='mybucket',
+            Key='the-key',
+            PartNumber=i,
+            UploadId=mpu_id,
+            Body=body,
+            ContentLength=len(body),
+        )
+        parts.append({"PartNumber": i, "ETag": part["ETag"]})
+
+    s3.complete_multipart_upload(
+        Bucket='mybucket',
+        Key='the-key',
+        UploadId=mpu_id,
+        MultipartUpload={"Parts": parts},
+    )
+
+    for i in range(1, n_parts + 1):
+        obj = s3.head_object(Bucket='mybucket', Key='the-key', PartNumber=i)
+        assert obj["ContentLength"] == part_size
+
+
 @mock_s3
 def test_boto3_put_object_with_tagging():
     s3 = boto3.client('s3', region_name='us-east-1')