fix(GraphQL): fix introspection completion bug

graphql/e2e/schema/introspection.graphql

@@ -0,0 +1,113 @@
+query {
+	__schema {
+		__typename
+		queryType {
+			name
+			__typename
+		}
+		mutationType {
+			name
+			__typename
+		}
+		subscriptionType {
+			name
+			__typename
+		}
+		types {
+			...FullType
+		}
+		directives {
+			__typename
+			name
+			locations
+			args {
+				...InputValue
+			}
+		}
+	}
+}
+fragment FullType on __Type {
+	kind
+	name
+	fields(includeDeprecated: true) {
+		__typename
+		name
+		args {
+			...InputValue
+			__typename
+		}
+		type {
+			...TypeRef
+			__typename
+		}
+		isDeprecated
+		deprecationReason
+	}
+	inputFields {
+		...InputValue
+		__typename
+	}
+	interfaces {
+		...TypeRef
+		__typename
+	}
+	enumValues(includeDeprecated: true) {
+		name
+		isDeprecated
+		deprecationReason
+		__typename
+	}
+	possibleTypes {
+		...TypeRef
+		__typename
+	}
+	__typename
+}
+fragment InputValue on __InputValue {
+	__typename
+	name
+	type {
+		...TypeRef
+	}
+	defaultValue
+}
+fragment TypeRef on __Type {
+	kind
+	name
+	ofType {
+		kind
+		name
+		ofType {
+			kind
+			name
+			ofType {
+				kind
+				name
+				ofType {
+					kind
+					name
+					ofType {
+						kind
+						name
+						ofType {
+							kind
+							name
+							ofType {
+								kind
+								name
+								__typename
+							}
+							__typename
+						}
+						__typename
+					}
+					__typename
+				}
+				__typename
+			}
+			__typename
+		}
+		__typename
+	}
+	__typename
+}

graphql/e2e/schema/schema_test.go

@@ -486,6 +486,36 @@ func TestUpdateGQLSchemaFields(t *testing.T) {
 	require.Equal(t, string(generatedSchema), updateResp.UpdateGQLSchema.GQLSchema.GeneratedSchema)
 }
 
+func TestIntrospection(t *testing.T) {
+	// note that both the types implement the same interface and have a field called `name`, which
+	// has exact same name as a field in full introspection query.
+	schema := `
+	interface Node {
+		id: ID!
+	}
+
+	type Human implements Node {
+		name: String
+	}
+
+	type Dog implements Node {
+		name: String
+	}`
+	updateGQLSchemaRequireNoErrors(t, schema, groupOneAdminServer)
+	query, err := ioutil.ReadFile("introspection.graphql")
+	require.NoError(t, err)
+
+	introspectionParams := &common.GraphQLParams{Query: string(query)}
+	resp := introspectionParams.ExecuteAsPost(t, groupOneServer)
+
+	// checking that there are no errors in the response, i.e., we always get some data in the
+	// introspection response.
+	require.Nilf(t, resp.Errors, "%s", resp.Errors)
+	require.NotEmpty(t, resp.Data)
+	// TODO: we should actually compare data here, but there seems to be some issue with either the
+	// introspection response or the JSON comparison. Needs deeper looking.
+}
+
 func updateGQLSchema(t *testing.T, schema, url string) *common.GraphQLResponse {
 	req := &common.GraphQLParams{
 		Query: `mutation updateGQLSchema($sch: String!) {

graphql/schema/wrappers.go

@@ -673,7 +673,15 @@ func (f *field) DgraphAlias() string {
 	// if this field is repeated, then it should be aliased using its dgraph predicate which will be
 	// unique across repeated fields
 	if f.op.inSchema.repeatedFieldNames[f.Name()] {
-		return f.DgraphPredicate()
+		dgraphAlias := f.DgraphPredicate()
+		// there won't be any dgraph predicate for fields in introspection queries, as they are not
+		// stored in dgraph. So we identify those fields using this condition, and just let the
+		// field name get returned for introspection query fields, because the raw data response is
+		// prepared for them using only the field name, so that is what should be used to pick them
+		// back up from that raw data response before completion is performed.
+		if dgraphAlias != "" {
+			return dgraphAlias
+		}
 	}
 	// if not repeated, alias it using its name
 	return f.Name()