utilities/extendSchema not appending SubscriptionType

[edispring]

We have an existing GraphQLSchema instance with no SubscriptionTypes and want to extend this schema with a new SubscriptionType. To extend we use the extendSchema utility. After extending the schema, the SubscriptionType is null on the new schema.

    const todoType = new GraphQLObjectType({
        name: 'Todo',
        description: 'A task to be completed',
        fields: {
            id: { type: GraphQLID },
            description: { type: GraphQLString },
            completed: { type: GraphQLBoolean },
        },
    });

    const queryType = new GraphQLObjectType({
        name: 'QueryType',
        fields: {
            todo: {
                type: todoType,
                args: {
                    id: { type: GraphQLID },
                },
            },
        },
    });

    // GraphQLSchema with no SubscriptionTypes
    const schema = new GraphQLSchema({
        query: queryType
    });

    const extension = `type Subscription {
      todoCompleted: Todo
    }`;
    
    const extendedSchema = extendSchema(schema, parse(extension));

    assert.ok(!!extendedSchema.getSubscriptionType()); // fails, extendedSchema.getSubscriptionType() is null

[leebyron]

Currently, extendSchema only extends existing types and does not add new root types to the schema - however this is certainly something to be investigated

[flchaux]

@leebyron no news on this ? I've the same issue with Mutation.