Temporarily fix the merger not returning correctly for Unions

See issue nautilus#74: nautilus#74

merge.go

@@ -33,6 +33,8 @@ func mergeSchemas(sources []*ast.Schema) (*ast.Schema, error) {
 		Directives:    map[string]*ast.DirectiveDefinition{},
 	}
 
+	unionSet := map[string]bool{}
+
 	// merging the schemas has to happen in 2 passes per definnition. The first groups definitions into different
 	// categories. Interfaces need to be validated before we can add the types that implement them
 	types := map[string][]*ast.Definition{}
@@ -92,8 +94,19 @@ func mergeSchemas(sources []*ast.Schema) (*ast.Schema, error) {
 				// use the declaration that we got from the new schema
 				result.Types[name] = definition
 
-				// register the type as an implementer of itself
-				result.AddPossibleType(name, definition)
+				if definition.Kind == ast.Union {
+					for _, possibleType := range definition.Types {
+						for _, typedef := range types[possibleType] {
+							if _, exists := unionSet[typedef.Name]; !exists {
+								unionSet[typedef.Name] = true
+								result.AddPossibleType(name, typedef)
+							}
+						}
+					}
+				} else {
+					// register the type as an implementer of itself
+					result.AddPossibleType(name, definition)
+				}
 
 				// each interface that this type implements needs to be registered
 				for _, iface := range definition.Interfaces {