chore: added simple get catalog entity

Signed-off-by: benjdlambert <ben@blam.sh>

plugins/catalog-backend/src/actions/createGetCatalogEntityAction.test.ts

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { createGetCatalogEntityAction } from './createGetCatalogEntityAction';
+import { catalogServiceMock } from '@backstage/plugin-catalog-node/testUtils';
+import { actionsRegistryServiceMock } from '@backstage/backend-test-utils/alpha';
+
+describe('createGetCatalogEntityAction', () => {
+  it('should throw an error if the entity is not found', async () => {
+    const mockActionsRegistry = actionsRegistryServiceMock();
+    const mockCatalog = catalogServiceMock();
+
+    createGetCatalogEntityAction({
+      catalog: mockCatalog,
+      actionsRegistry: mockActionsRegistry,
+    });
+
+    await expect(
+      mockActionsRegistry.invoke({
+        id: 'test:get-catalog-entity',
+        input: { name: 'test' },
+      }),
+    ).rejects.toThrow(`No entity found with name "test"`);
+  });
+
+  it('should throw an error if theres multiple entities found', async () => {
+    const mockActionsRegistry = actionsRegistryServiceMock();
+    const mockCatalog = catalogServiceMock({
+      entities: [
+        {
+          kind: 'Component',
+          apiVersion: 'backstage.io/v1alpha1',
+          metadata: {
+            name: 'test',
+            namespace: 'default',
+          },
+          spec: {
+            type: 'component',
+          },
+        },
+        {
+          kind: 'API',
+          apiVersion: 'backstage.io/v1alpha1',
+          metadata: {
+            name: 'test',
+            namespace: 'default',
+          },
+        },
+      ],
+    });
+
+    createGetCatalogEntityAction({
+      catalog: mockCatalog,
+      actionsRegistry: mockActionsRegistry,
+    });
+
+    await expect(
+      mockActionsRegistry.invoke({
+        id: 'test:get-catalog-entity',
+        input: { name: 'test' },
+      }),
+    ).rejects.toThrow(
+      `Multiple entities found with name "test", please provide more specific filters. Entities found: "component:default/test", "api:default/test"`,
+    );
+  });
+});

plugins/catalog-backend/src/actions/createGetCatalogEntityAction.ts

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { ActionsRegistryService } from '@backstage/backend-plugin-api/alpha';
+import { stringifyEntityRef } from '@backstage/catalog-model';
+import { InputError } from '@backstage/errors';
+import { CatalogService } from '@backstage/plugin-catalog-node';
+
+export const createGetCatalogEntityAction = ({
+  catalog,
+  actionsRegistry,
+}: {
+  catalog: CatalogService;
+  actionsRegistry: ActionsRegistryService;
+}) => {
+  actionsRegistry.register({
+    name: 'get-catalog-entity',
+    title: 'Get Catalog Entity',
+    description: `
+This allows you to get a single entity from the software catalog.
+Each entity in the software catalog has a unique name, kind, and namespace. The default namespace is "default".
+Each entity is identified by a unique entity reference, which is a string of the form "kind:namespace/name".
+    `,
+    schema: {
+      input: z =>
+        z.object({
+          kind: z
+            .string()
+            .describe(
+              'The kind of the entity to query. If the kind is unknown it can be omitted.',
+            )
+            .optional(),
+          namespace: z
+            .string()
+            .describe(
+              'The namespace of the entity to query. If the namespace is unknown it can be omitted.',
+            )
+            .optional(),
+          name: z.string().describe('The name of the entity to query'),
+        }),
+      // TODO: is there a better way to do this?
+      output: z => z.object({}).passthrough(),
+    },
+    action: async ({ input, credentials }) => {
+      const filter: Record<string, string> = { 'metadata.name': input.name };
+
+      if (input.kind) {
+        filter.kind = input.kind;
+      }
+
+      if (input.namespace) {
+        filter['metadata.namespace'] = input.namespace;
+      }
+
+      const { items } = await catalog.queryEntities(
+        { filter },
+        {
+          credentials,
+        },
+      );
+
+      if (items.length === 0) {
+        throw new InputError(`No entity found with name "${input.name}"`);
+      }
+
+      if (items.length > 1) {
+        throw new Error(
+          `Multiple entities found with name "${
+            input.name
+          }", please provide more specific filters. Entities found: ${items
+            .map(item => `"${stringifyEntityRef(item)}"`)
+            .join(', ')}`,
+        );
+      }
+
+      const [entity] = items;
+
+      return {
+        output: entity,
+      };
+    },
+  });
+};

plugins/catalog-backend/src/service/CatalogPlugin.ts

@@ -22,6 +22,7 @@ import { ForwardedError } from '@backstage/errors';
 import {
   CatalogProcessor,
   CatalogProcessorParser,
+  catalogServiceRef,
   EntityProvider,
   LocationAnalyzer,
   PlaceholderResolver,
@@ -43,6 +44,8 @@ import { eventsServiceRef } from '@backstage/plugin-events-node';
 import { Permission } from '@backstage/plugin-permission-common';
 import { merge } from 'lodash';
 import { CatalogBuilder } from './CatalogBuilder';
+import { actionsRegistryServiceRef } from '@backstage/backend-plugin-api/alpha';
+import { createGetCatalogEntityAction } from '../actions/createGetCatalogEntityAction';
 
 class CatalogLocationsExtensionPointImpl
   implements CatalogLocationsExtensionPoint
@@ -237,6 +240,8 @@ export const catalogPlugin = createBackendPlugin({
         httpAuth: coreServices.httpAuth,
         auditor: coreServices.auditor,
         events: eventsServiceRef,
+        catalog: catalogServiceRef,
+        actionsRegistry: actionsRegistryServiceRef,
       },
       async init({
         logger,
@@ -250,6 +255,8 @@ export const catalogPlugin = createBackendPlugin({
         scheduler,
         auth,
         httpAuth,
+        catalog,
+        actionsRegistry,
         auditor,
         events,
       }) {
@@ -313,6 +320,11 @@ export const catalogPlugin = createBackendPlugin({
         }
 
         httpRouter.use(router);
+
+        createGetCatalogEntityAction({
+          catalog,
+          actionsRegistry,
+        });
       },
     });
   },