Merge pull request #15893 from bernt-matthias/fix/cached_explicit_sin…

…gularity_container_description

[22.01] cached_explicit_singularity: needs to copy container description

lib/galaxy/tool_util/deps/container_resolvers/explicit.py

@@ -1,4 +1,5 @@
 """This module describes the :class:`ExplicitContainerResolver` ContainerResolver plugin."""
+import copy
 import logging
 import os
 
@@ -77,11 +78,10 @@ def resolve(self, enabled_container_types, tool_info, install=False, **kwds):
         hence the container_description hack here.
         """
         for container_description in tool_info.container_descriptions:  # type: ContainerDescription
+            container_description = copy.copy(container_description)
             if container_description.type == 'docker':
-                desc_dict = container_description.to_dict()
-                desc_dict['type'] = self.container_type
-                desc_dict['identifier'] = f"docker://{container_description.identifier}"
-                container_description = container_description.from_dict(desc_dict)
+                container_description.type = self.container_type
+                container_description.identifier = f"docker://{container_description.identifier}"
             if not self._container_type_enabled(container_description, enabled_container_types):
                 return None
             if not self.cli_available: