Allow empty prefix in Filter

minio/commonconfig.py

@@ -179,8 +179,6 @@ def __init__(self, and_operator=None, prefix=None, tag=None):
         )
         if not valid:
             raise ValueError("only one of and, prefix or tag must be provided")
-        if prefix is not None and not prefix:
-            raise ValueError("prefix must not be empty")
         self._and_operator = and_operator
         self._prefix = prefix
         self._tag = tag

minio/xml.py

@@ -77,7 +77,7 @@ def findtext(element, name, strict=False):
         if strict:
             raise ValueError("XML element <{0}> not found".format(name))
         return None
-    return element.text
+    return element.text or ""
 
 
 def unmarshal(cls, xmlstring):

tests/unit/lifecycleconfig_test.py

@@ -41,6 +41,18 @@ def test_config(self):
         )
         xml.marshal(config)
 
+        config = LifecycleConfig(
+            [
+                Rule(
+                    ENABLED,
+                    rule_filter=Filter(prefix=""),
+                    rule_id="rule",
+                    expiration=Expiration(days=365),
+                ),
+            ],
+        )
+        xml.marshal(config)
+
         config = xml.unmarshal(
             LifecycleConfig,
             """<LifeCycleConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
@@ -68,3 +80,20 @@ def test_config(self):
 </LifeCycleConfiguration>""",
         )
         xml.marshal(config)
+
+        config = xml.unmarshal(
+            LifecycleConfig,
+            """<LifeCycleConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
+  <Rule>
+    <ID>DeleteAfterBecomingNonCurrent</ID>
+    <Filter>
+       <Prefix></Prefix>
+    </Filter>
+    <Status>Enabled</Status>
+    <NoncurrentVersionExpiration>
+      <NoncurrentDays>100</NoncurrentDays>
+    </NoncurrentVersionExpiration>
+  </Rule>
+</LifeCycleConfiguration>""",
+        )
+        xml.marshal(config)