data.py.diff

$ git diff lib/galaxy/datatypes/data.py
diff --git a/lib/galaxy/datatypes/data.py b/lib/galaxy/datatypes/data.py
index 0931e2b..d9410f9 100644
--- a/lib/galaxy/datatypes/data.py
+++ b/lib/galaxy/datatypes/data.py
@@ -603,12 +603,18 @@ class Data(object):
         # Generate parameter dictionary
         params = {}
         # determine input parameter name and add to params
-        input_name = 'input1'
+        input_names = []
         for key, value in converter.inputs.items():
             if deps and value.name in deps:
                 params[value.name] = deps[value.name]
             elif value.type == 'data':
-                input_name = key
+                input_names.append(key)
+        if not input_names:
+            raise Exception("No input data parameter found in %s" % converter.name)
+        elif len(input_names) == 1:
+            input_name = input_names[0]
+        else:
+            raise Exception("Found %d unassigned input data parameters in %s, expected 1: dependencies may be missing" % (len(input_names), converter.name))
         # add potentially required/common internal tool parameters e.g. '__job_resource'
         if target_context:
             for key, value in target_context.items():