Merge pull request #91 from gmac/abstract-typename-hints

Always add __typename to abstract types

.gitignore

@@ -2,4 +2,5 @@
 .vscode
 .history
 .idea
+.DS_Store
 coverage.out

plan.go

@@ -262,6 +262,11 @@ func extractSelectionSet(ctx *PlanningContext, insertionPoint []string, parentTy
 				break
 			}
 		}
+		selectionSetResult = append(selectionSetResult, &ast.Field{
+			Alias: "__typename",
+			Name: "__typename",
+			Definition: &ast.FieldDefinition{Name: "__typename", Type: ast.NamedType("String", nil)},
+		})
 	// Otherwise, add an id selection to boundary types where the result
 	// will be merged with another step (i.e.: has children or is a child step).
 	} else if parentType != queryObjectName &&

plan_test.go

@@ -496,6 +496,7 @@ func TestQueryPlanExpandAbstractTypesWithPossibleBoundaryIds(t *testing.T) {
 		"name",
 		"... on Lion { _id: id }",
 		"... on Snake { _id: id }",
+		"__typename",
 	}
 	PlanTestFixture3.CheckUnorderedRootFieldSelections(t, query, rootFieldSelections)
 }
@@ -519,6 +520,7 @@ func TestQueryPlanInlineFragmentSpreadOfInterface(t *testing.T) {
 		"... on Snake { _id: id }",
 		"... on Lion { maneColor __typename }",
 		"... on Snake { _id: id __typename }",
+		"__typename",
 	}
 	PlanTestFixture3.CheckUnorderedRootFieldSelections(t, query, rootFieldSelections)
 }
@@ -638,7 +640,7 @@ func TestQueryPlanSupportsUnions(t *testing.T) {
         {
           "ServiceURL": "A",
           "ParentType": "Query",
-          "SelectionSet": "{ animals { ... on Dog { name __typename } ... on Cat { name __typename } ... on Snake { name __typename } } }",
+          "SelectionSet": "{ animals { ... on Dog { name __typename } ... on Cat { name __typename } ... on Snake { name __typename } __typename } }",
           "InsertionPoint": null,
           "Then": null
         }