Keep target field in entities output

Signed-off-by: Johan Haals <johan.haals@gmail.com>

plugins/catalog-backend/src/service/DefaultEntitiesCatalog.test.ts

@@ -469,6 +469,62 @@ describe('DefaultEntitiesCatalog', () => {
         expect(entities.length).toBe(0);
       },
     );
+
+    it.each(databases.eachSupportedId())(
+      'should return both target and targetRef for entities',
+      async databaseId => {
+        const { knex } = await createDatabase(databaseId);
+        await addEntity(
+          knex,
+          {
+            apiVersion: 'a',
+            kind: 'k',
+            metadata: { name: 'one' },
+            spec: {},
+            relations: [{ type: 'r', targetRef: 'x:y/z' } as any],
+          },
+          [],
+        );
+        await addEntity(
+          knex,
+          {
+            apiVersion: 'a',
+            kind: 'k',
+            metadata: { name: 'two' },
+            spec: {},
+            relations: [
+              {
+                type: 'r',
+                target: { kind: 'x', namespace: 'y', name: 'z' },
+              } as any,
+            ],
+          },
+          [],
+        );
+        const catalog = new DefaultEntitiesCatalog(knex);
+
+        const { entities } = await catalog.entities();
+
+        expect(
+          entities.find(e => e.metadata.name === 'one')!.relations,
+        ).toEqual([
+          {
+            type: 'r',
+            targetRef: 'x:y/z',
+            target: { kind: 'x', namespace: 'y', name: 'z' },
+          },
+        ]);
+        expect(
+          entities.find(e => e.metadata.name === 'two')!.relations,
+        ).toEqual([
+          {
+            type: 'r',
+            targetRef: 'x:y/z',
+            target: { kind: 'x', namespace: 'y', name: 'z' },
+          },
+        ]);
+      },
+    );
   });
 
   describe('removeEntityByUid', () => {

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

@@ -14,7 +14,11 @@
  * limitations under the License.
  */
 
-import { Entity, stringifyEntityRef } from '@backstage/catalog-model';
+import {
+  Entity,
+  parseEntityRef,
+  stringifyEntityRef,
+} from '@backstage/catalog-model';
 import { InputError, NotFoundError } from '@backstage/errors';
 import { Knex } from 'knex';
 import lodash from 'lodash';
@@ -200,6 +204,28 @@ export class DefaultEntitiesCatalog implements EntitiesCatalog {
       entities = entities.map(e => request.fields!(e));
     }
 
+    // TODO(freben): This is added as a compatibility guarantee, until we can be
+    // sure that all adopters have re-stitched their entities so that the new
+    // targetRef field is present on them, and that they have stopped consuming
+    // the now-removed old field
+    // TODO(jhaals): Remove this in April 2021
+    for (const entity of entities) {
+      if (entity.relations) {
+        for (const relation of entity.relations as any) {
+          if (!relation.targetRef && relation.target) {
+            // This is the case where an old-form entity, not yet stitched with
+            // the updated code, was in the database
+            relation.targetRef = stringifyEntityRef(relation.target);
+          } else if (!relation.target && relation.targetRef) {
+            // This is the case where a new-form entity, stitched with the
+            // updated code, was in the database but we still want to produce
+            // the old data shape as well for compatibility reasons
+            relation.target = parseEntityRef(relation.targetRef);
+          }
+        }
+      }
+    }
+
     return {
       entities,
       pageInfo,