fix(GraphQL) fix empty type Query with single extended type definit…

…ion in the schema. (#7517)

graphql/schema/gqlschema.go

@@ -2428,6 +2428,17 @@ func generateUnionString(typ *ast.Definition) string {
 		strings.Join(typ.Types, " | "))
 }
 
+func hasStringifiableFields(typ *ast.Definition) bool {
+	queriesToWrite := false
+	for _, fld := range typ.Fields {
+		if !strings.HasPrefix(fld.Name, "__") {
+			queriesToWrite = true
+			break
+		}
+	}
+	return queriesToWrite
+}
+
 // Stringify the schema as a GraphQL SDL string.  It's assumed that the schema was
 // built by completeSchema, and so contains an original set of definitions, the
 // definitions from schemaExtras and generated types, queries and mutations.
@@ -2554,7 +2565,7 @@ func Stringify(schema *ast.Schema, originalTypes []string, apolloServiceQuery bo
 		x.Check2(sch.WriteString(input.String()))
 	}
 
-	if len(schema.Query.Fields) > 0 {
+	if hasStringifiableFields(schema.Query) {
 		x.Check2(sch.WriteString(
 			"#######################\n# Generated Query\n#######################\n\n"))
 		x.Check2(sch.WriteString(generateObjectString(schema.Query) + "\n"))

graphql/schema/testdata/apolloservice/input/single-extended-type.graphql

@@ -0,0 +1,4 @@
+extend type Product @key(fields: "id") {
+    id: String! @id @external
+    name: String!
+}

graphql/schema/testdata/apolloservice/output/single-extended-type.graphql

@@ -0,0 +1,349 @@
+#######################
+# Input Schema
+#######################
+
+type Product @key(fields: "id") @extends {
+	id: String! @id @external
+	name: String!
+}
+
+#######################
+# Extended Definitions
+#######################
+
+"""
+The Int64 scalar type represents a signed 64‐bit numeric non‐fractional value.
+Int64 can represent values in range [-(2^63),(2^63 - 1)].
+"""
+scalar Int64
+
+"""
+The DateTime scalar type represents date and time as a string in RFC3339 format.
+For example: "1985-04-12T23:20:50.52Z" represents 20 minutes and 50.52 seconds after the 23rd hour of April 12th, 1985 in UTC.
+"""
+scalar DateTime
+
+input IntRange{
+	min: Int!
+	max: Int!
+}
+
+input FloatRange{
+	min: Float!
+	max: Float!
+}
+
+input Int64Range{
+	min: Int64!
+	max: Int64!
+}
+
+input DateTimeRange{
+	min: DateTime!
+	max: DateTime!
+}
+
+input StringRange{
+	min: String!
+	max: String!
+}
+
+enum DgraphIndex {
+	int
+	int64
+	float
+	bool
+	hash
+	exact
+	term
+	fulltext
+	trigram
+	regexp
+	year
+	month
+	day
+	hour
+	geo
+}
+
+input AuthRule {
+	and: [AuthRule]
+	or: [AuthRule]
+	not: AuthRule
+	rule: String
+}
+
+enum HTTPMethod {
+	GET
+	POST
+	PUT
+	PATCH
+	DELETE
+}
+
+enum Mode {
+	BATCH
+	SINGLE
+}
+
+input CustomHTTP {
+	url: String!
+	method: HTTPMethod!
+	body: String
+	graphql: String
+	mode: Mode
+	forwardHeaders: [String!]
+	secretHeaders: [String!]
+	introspectionHeaders: [String!]
+	skipIntrospection: Boolean
+}
+
+type Point {
+	longitude: Float!
+	latitude: Float!
+}
+
+input PointRef {
+	longitude: Float!
+	latitude: Float!
+}
+
+input NearFilter {
+	distance: Float!
+	coordinate: PointRef!
+}
+
+input PointGeoFilter {
+	near: NearFilter
+	within: WithinFilter
+}
+
+type PointList {
+	points: [Point!]!
+}
+
+input PointListRef {
+	points: [PointRef!]!
+}
+
+type Polygon {
+	coordinates: [PointList!]!
+}
+
+input PolygonRef {
+	coordinates: [PointListRef!]!
+}
+
+type MultiPolygon {
+	polygons: [Polygon!]!
+}
+
+input MultiPolygonRef {
+	polygons: [PolygonRef!]!
+}
+
+input WithinFilter {
+	polygon: PolygonRef!
+}
+
+input ContainsFilter {
+	point: PointRef
+	polygon: PolygonRef
+}
+
+input IntersectsFilter {
+	polygon: PolygonRef
+	multiPolygon: MultiPolygonRef
+}
+
+input PolygonGeoFilter {
+	near: NearFilter
+	within: WithinFilter
+	contains: ContainsFilter
+	intersects: IntersectsFilter
+}
+
+input GenerateQueryParams {
+	get: Boolean
+	query: Boolean
+	password: Boolean
+	aggregate: Boolean
+}
+
+input GenerateMutationParams {
+	add: Boolean
+	update: Boolean
+	delete: Boolean
+}
+
+directive @hasInverse(field: String!) on FIELD_DEFINITION
+directive @search(by: [DgraphIndex!]) on FIELD_DEFINITION
+directive @dgraph(type: String, pred: String) on OBJECT | INTERFACE | FIELD_DEFINITION
+directive @id on FIELD_DEFINITION
+directive @withSubscription on OBJECT | INTERFACE | FIELD_DEFINITION
+directive @secret(field: String!, pred: String) on OBJECT | INTERFACE
+directive @remote on OBJECT | INTERFACE | UNION | INPUT_OBJECT | ENUM
+directive @remoteResponse(name: String) on FIELD_DEFINITION
+directive @cascade(fields: [String]) on FIELD
+directive @lambda on FIELD_DEFINITION
+directive @cacheControl(maxAge: Int!) on QUERY
+
+input IntFilter {
+	eq: Int
+	in: [Int]
+	le: Int
+	lt: Int
+	ge: Int
+	gt: Int
+	between: IntRange
+}
+
+input Int64Filter {
+	eq: Int64
+	in: [Int64]
+	le: Int64
+	lt: Int64
+	ge: Int64
+	gt: Int64
+	between: Int64Range
+}
+
+input FloatFilter {
+	eq: Float
+	in: [Float]
+	le: Float
+	lt: Float
+	ge: Float
+	gt: Float
+	between: FloatRange
+}
+
+input DateTimeFilter {
+	eq: DateTime
+	in: [DateTime]
+	le: DateTime
+	lt: DateTime
+	ge: DateTime
+	gt: DateTime
+	between: DateTimeRange
+}
+
+input StringTermFilter {
+	allofterms: String
+	anyofterms: String
+}
+
+input StringRegExpFilter {
+	regexp: String
+}
+
+input StringFullTextFilter {
+	alloftext: String
+	anyoftext: String
+}
+
+input StringExactFilter {
+	eq: String
+	in: [String]
+	le: String
+	lt: String
+	ge: String
+	gt: String
+	between: StringRange
+}
+
+input StringHashFilter {
+	eq: String
+	in: [String]
+}
+
+#######################
+# Generated Types
+#######################
+
+type AddProductPayload {
+	product(filter: ProductFilter, order: ProductOrder, first: Int, offset: Int): [Product]
+	numUids: Int
+}
+
+type DeleteProductPayload {
+	product(filter: ProductFilter, order: ProductOrder, first: Int, offset: Int): [Product]
+	msg: String
+	numUids: Int
+}
+
+type ProductAggregateResult {
+	count: Int
+	idMin: String
+	idMax: String
+	nameMin: String
+	nameMax: String
+}
+
+type UpdateProductPayload {
+	product(filter: ProductFilter, order: ProductOrder, first: Int, offset: Int): [Product]
+	numUids: Int
+}
+
+#######################
+# Generated Enums
+#######################
+
+enum ProductHasFilter {
+	id
+	name
+}
+
+enum ProductOrderable {
+	id
+	name
+}
+
+#######################
+# Generated Inputs
+#######################
+
+input AddProductInput {
+	id: String!
+	name: String!
+}
+
+input ProductFilter {
+	id: StringHashFilter
+	has: [ProductHasFilter]
+	and: [ProductFilter]
+	or: [ProductFilter]
+	not: ProductFilter
+}
+
+input ProductOrder {
+	asc: ProductOrderable
+	desc: ProductOrderable
+	then: ProductOrder
+}
+
+input ProductPatch {
+	name: String
+}
+
+input ProductRef {
+	id: String
+	name: String
+}
+
+input UpdateProductInput {
+	filter: ProductFilter!
+	set: ProductPatch
+	remove: ProductPatch
+}
+
+#######################
+# Generated Mutations
+#######################
+
+type Mutation {
+	addProduct(input: [AddProductInput!]!, upsert: Boolean): AddProductPayload
+	updateProduct(input: UpdateProductInput!): UpdateProductPayload
+	deleteProduct(filter: ProductFilter!): DeleteProductPayload
+}
+