service: improve read_latest

* Allows to fetch the latest version by
  passing the parent id
* closes zenodo/rdm-project#174

invenio_drafts_resources/services/records/service.py

@@ -196,9 +196,23 @@ def read_draft(self, identity, id_, expand=False):
         )
 
     def read_latest(self, identity, id_, expand=False):
-        """Retrieve latest record."""
+        """Retrieve latest record.
+
+        If provided with the ID of a parent record it will resolve it and return the latest version of the record.
+        """
         # Resolve and require permission
-        record = self.record_cls.pid.resolve(id_)
+
+        try:
+            record = self.record_cls.pid.resolve(id_)
+        except NoResultFound:
+            parent_pid = self.record_cls.parent_record_cls.pid.resolve(id_)
+            version_state = self.record_cls.versions.resolve(
+                parent_id=parent_pid.pid.object_uuid
+            )
+            if version_state and version_state.latest_id:
+                record = self.record_cls.get_record(version_state.latest_id)
+            else:
+                raise NoResultFound("Failed to fetch the record versions.")
 
         # Retrieve latest if record is not
         if not record.versions.is_latest:

tests/resources/test_record_resource.py

@@ -147,7 +147,7 @@ def test_search_versions(client, headers, input_data, location, search_clear):
 
 
 def test_create_publish_new_revision(
-    client, headers, input_data, location, search_clear
+    app, db, client, headers, input_data, location, search_clear
 ):
     """Test draft creation of an existing record and publish it."""
     recid = _create_and_publish(client, headers, input_data)