Add docs example of using encodeEntityId

Signed-off-by: Dmitriy Lazarev <w@kich.dev>

plugins/graphql-backend-module-catalog/README.md

@@ -17,10 +17,10 @@ Some key features are currently missing. These features may change the schema in
 
 - [GraphQL modules](#graphql-modules)
   - [Backstage Plugins](#backstage-plugins)
-  - [Experimental Backend System](#experimental-backend-system)
+  - [Backend System](#backend-system)
 - [Directives API](#directives-api)
   - [`@relation` directive](#relation-directive)
-- [Catalog Data loader](#catalog-data-loader-advanced)
+- [Custom GraphQL Resolvers](#custom-graphql-resolvers)
 
 ## GraphQL modules
 
@@ -46,13 +46,16 @@ export default async function createPlugin(
     logger: env.logger,
     modules: [Catalog],
     loaders: { ...createCatalogLoader(env.catalogClient) },
+    // You might want to pass catalog client to the context
+    // and use it in resolvers, but it's not required
+    context: ctx => ({ ...ctx, catalog: env.catalogClient }),
   });
 }
 ```
 
-### Experimental Backend System
+### Backend System
 
-For the [experimental backend system](https://backstage.io/docs/plugins/experimental-backend),
+For the [backend system](https://backstage.io/docs/backend-system/),
 you can add them as a plugin modules:
 
 - To use `Catalog` GraphQL module
@@ -122,6 +125,46 @@ type System {
 }
 ```
 
+## Custom GraphQL Resolvers
+
+If you need to implement complicated logic for some fields and can't be
+achieved with available [directives][directives-api], you can write
+your own resolvers. To do this, you need to define a resolver function
+in your [GraphQL module](../graphql-backend/README.md#custom-graphql-module):
+
+```ts
+import { createModule } from "graphql-modules";
+import type { CatalogClient, QueryEntitiesRequest } from '@backstage/catalog-client';
+import { encodeEntityId } from '@frontside/backstage-plugin-graphql-backend-module-catalog';
+
+export const myModule = createModule({
+  /* ... */
+  resolvers: {
+    Task: {
+      // This resolver utilize 3rd party api to get entity ref and then encodes it to NodeId
+      // Which will be resolved to an entity
+      entity: async (_, args, { taskAPI }) => {
+        const response = await taskAPI.getTask(args.taskId);
+        return { id: encodeEntityId(response.entityRef) };
+      },
+    },
+    Query: {
+      // Here you can use catalog client to query entities
+      entities: async (
+        _: any,
+        args: QueryEntitiesRequest,
+        // If you aren't using Backstage Backend System https://backstage.io/docs/backend-system/
+        // This requires you to pass catalog client to the context
+        { catalog }: { catalog: CatalogClient }
+      ): Promise<{ id: string }[]> => {
+        const { items: entities } = await catalog.queryEntities(args);
+        return entities.map(entity => ({ id: encodeEntityId(entity) }));
+      },
+    },
+  },
+});
+```
+
 [graphql-backend]: ../graphql-backend/README.md
 [graphql-modules]: https://the-guild.dev/graphql/modules
 [relay]: https://relay.dev/docs/guides/graphql-server-specification

plugins/graphql-backend-module-catalog/src/catalogModule.ts

@@ -1,6 +1,7 @@
 import { createBackendModule } from '@backstage/backend-plugin-api';
 import { catalogServiceRef } from '@backstage/plugin-catalog-node/alpha';
 import {
+  graphqlContextExtensionPoint,
   graphqlLoadersExtensionPoint,
   graphqlModulesExtensionPoint,
 } from '@frontside/backstage-plugin-graphql-backend';
@@ -17,10 +18,12 @@ export const graphqlModuleCatalog = createBackendModule({
         catalog: catalogServiceRef,
         modules: graphqlModulesExtensionPoint,
         loaders: graphqlLoadersExtensionPoint,
+        context: graphqlContextExtensionPoint,
       },
-      async init({ catalog, modules, loaders }) {
+      async init({ catalog, modules, loaders, context }) {
         modules.addModules([Catalog]);
         loaders.addLoaders(createCatalogLoader(catalog));
+        context.setContext(ctx => ({ ...ctx, catalog }));
       },
     });
   },

plugins/graphql-backend-module-catalog/src/relationModule.ts

@@ -1,6 +1,7 @@
 import { createBackendModule } from '@backstage/backend-plugin-api';
 import { catalogServiceRef } from '@backstage/plugin-catalog-node/alpha';
 import {
+  graphqlContextExtensionPoint,
   graphqlLoadersExtensionPoint,
   graphqlModulesExtensionPoint,
 } from '@frontside/backstage-plugin-graphql-backend';
@@ -17,10 +18,12 @@ export const graphqlModuleRelationResolver = createBackendModule({
         catalog: catalogServiceRef,
         modules: graphqlModulesExtensionPoint,
         loaders: graphqlLoadersExtensionPoint,
+        context: graphqlContextExtensionPoint,
       },
-      async init({ catalog, modules, loaders }) {
+      async init({ catalog, modules, loaders, context }) {
         modules.addModules([Relation]);
         loaders.addLoaders(createCatalogLoader(catalog));
+        context.setContext(ctx => ({ ...ctx, catalog }));
       },
     });
   },

plugins/graphql-backend/README.md

@@ -12,7 +12,7 @@ At a minimum, you should install the [graphql-backend-module-catalog][] which ad
 schema elements to access the [Backstage Catalog][backstage-catalog] via GraphQL
 
 - [Backstage Plugins](./docs/backend-plugins.md#getting-started)
-- [Experimental Backend System](#experimental-backend-system)
+- [Backend System](#backend-system)
   - [Getting started](#getting-started)
   - [GraphQL Modules](#graphql-modules)
     - [Custom GraphQL Module](#custom-graphql-module)
@@ -25,7 +25,7 @@ schema elements to access the [Backstage Catalog][backstage-catalog] via GraphQL
   - [Backstage API Docs](#backstage-api-docs)
 - [Questions](#questions)
 
-## Experimental Backend System
+## Backend System
 
 This approach is suitable for the new [Backstage backend system](https://backstage.io/docs/backend-system/).
 For the current [Backstage plugins system](https://backstage.io/docs/plugins/backend-plugin) see [Backstage Plugins](./docs/backend-plugins.md#getting-started)