Merge pull request #273321 from dlepow/gqlu

[APIM] GraphQL union and interface types

Author: prmerger-automator[bot]

articles/api-management/configure-graphql-resolver.md

@@ -6,7 +6,7 @@ author: dlepow
 
 ms.service: api-management
 ms.topic: article
-ms.date: 06/08/2023
+ms.date: 05/02/2024
 ms.author: danlep
 ---
 
@@ -29,6 +29,7 @@ Currently, API Management supports resolvers that can access the following data
 * Each resolver resolves data for a single field. To resolve data for multiple fields, configure a separate resolver for each.
 * Resolver-scoped policies are evaluated *after* any `inbound` and `backend` policies in the policy execution pipeline. They don't inherit policies from other scopes. For more information, see [Policies in API Management](api-management-howto-policies.md).
 * You can configure API-scoped policies for a GraphQL API, independent of the resolver-scoped policies. For example, add a [validate-graphql-request](validate-graphql-request-policy.md) policy to the `inbound` scope to validate the request before the resolver is invoked. Configure API-scoped policies on the **API policies** tab for the API.
+* To support interface and union types in GraphQL resolvers, the backend response must either already contain the `__typename` field, or be altered using the [set-body](set-body-policy.md) policy to include `__typename`.
 
 ## Prerequisites
 

articles/api-management/graphql-apis-overview.md

@@ -6,7 +6,7 @@ author: dlepow
 
 ms.service: api-management
 ms.topic: conceptual
-ms.date: 09/18/2023
+ms.date: 05/05/2024
 ms.author: danlep
 ---
 
@@ -41,12 +41,13 @@ The GraphQL specification explicitly solves common issues experienced by client
 
 Using a GraphQL API, the client app can specify the data they need to render a page in a query document that is sent as a single request to a GraphQL service. A client app can also subscribe to data updates pushed from the GraphQL service in real time.
 
-## Schema and operation types
+## Schema and types
 
 In API Management, add a GraphQL API from a GraphQL schema, either retrieved from a backend GraphQL API endpoint or uploaded by you. A GraphQL schema describes:
 
 * Data object types and fields that clients can request from a GraphQL API
 * Operation types allowed on the data, such as queries 
+* Other types, such as unions and interfaces, that provide additional flexibility and control over the data
 
 For example, a basic GraphQL schema for user data and a query for all users might look like:
 
@@ -61,17 +62,23 @@ type User {
 }
 ```
 
-API Management supports the following operation types in GraphQL schemas. For more information about these operation types, see the [GraphQL specification](https://spec.graphql.org/October2021/#sec-Subscription-Operation-Definitions).
+### Operation types
+
+API Management supports the following operation types in GraphQL schemas. For more information about these operation types, see the [GraphQL specification](https://spec.graphql.org/October2021/#sec-Root-Operation-Types).
 
 * **Query** - Fetches data, similar to a `GET` operation in REST
 *  **Mutation** - Modifies server-side data, similar to a `PUT` or `PATCH` operation in REST
 * **Subscription** - Enables notifying subscribed clients in real time about changes to data on the GraphQL service
 
     For example, when data is modified via a GraphQL mutation, subscribed clients could be automatically notified about the change. 
 
-> [!IMPORTANT]
-> API Management supports subscriptions implemented using  the [graphql-ws](https://github.com/enisdenjo/graphql-ws) WebSocket protocol. Queries and mutations aren't supported over WebSocket.
-> 
+    > [!IMPORTANT]
+    > API Management supports subscriptions implemented using  the [graphql-ws](https://github.com/enisdenjo/graphql-ws) WebSocket protocol. Queries and mutations aren't supported over WebSocket.
+    > 
+
+### Other types
+
+API Management supports the [union](https://spec.graphql.org/October2021/#sec-Unions) and [interface](https://spec.graphql.org/October2021/#sec-Interfaces) types in GraphQL schemas.
 
 ## Resolvers
 

articles/api-management/http-data-source-policy.md

@@ -6,7 +6,7 @@ author: dlepow
 
 ms.service: api-management
 ms.topic: article
-ms.date: 03/19/2024
+ms.date: 05/02/2024
 ms.author: danlep
 ---
 
@@ -97,7 +97,6 @@ The `http-data-source` resolver policy configures the HTTP request and optionall
 
 * To configure and manage a resolver with this policy, see [Configure a GraphQL resolver](configure-graphql-resolver.md).
 * This policy is invoked only when resolving a single field in a matching GraphQL operation type in the schema. 
-* This policy supports GraphQL [union types](https://spec.graphql.org/October2021/#sec-Unions).
 
 ## Examples