don't surface non-FetchErrors

It makes sense to gracefully show an error that was actually related to fetching
data from Kubernetes, but if the error is happening for some other exotic
reason, the default error handling logic in Backstage should take over and
log/manage it appropriately.

Signed-off-by: Jamie Klassen <jklassen@vmware.com>

plugins/kubernetes-backend/src/service/KubernetesFanOutHandler.test.ts

@@ -757,6 +757,27 @@ describe('getKubernetesObjectsByEntity', () => {
       ],
     });
   });
+  it('fails when fetcher rejects with a non-FetchError', async () => {
+    const nonFetchError = new Error('not a fetch error');
+    getClustersByEntity.mockResolvedValue({
+      clusters: [
+        {
+          name: 'test-cluster',
+          authProvider: 'serviceAccount',
+          skipMetricsLookup: true,
+        },
+      ],
+    });
+    fetchObjectsForService.mockRejectedValue(nonFetchError);
+
+    const sut = getKubernetesFanOutHandler([]);
+
+    const result = sut.getKubernetesObjectsByEntity({
+      entity,
+      auth: {},
+    });
+    await expect(result).rejects.toThrow(nonFetchError);
+  });
   describe('with a real fetcher', () => {
     const worker = setupServer();
     setupRequestMockHandlers(worker);

plugins/kubernetes-backend/src/service/KubernetesFanOutHandler.ts

@@ -274,15 +274,20 @@ export class KubernetesFanOutHandler {
             namespace,
           })
           .then(result => this.getMetricsForPods(clusterDetailsItem, result))
-          .catch((e): responseWithMetrics => {
-            return [
-              {
-                errors: [{ errorType: 'FETCH_ERROR', message: e.message }],
-                responses: [],
-              },
-              [],
-            ];
-          })
+          .catch(
+            (e): Promise<responseWithMetrics> =>
+              e.name === 'FetchError'
+                ? Promise.resolve([
+                    {
+                      errors: [
+                        { errorType: 'FETCH_ERROR', message: e.message },
+                      ],
+                      responses: [],
+                    },
+                    [],
+                  ])
+                : Promise.reject(e),
+          )
           .then(r => this.toClusterObjects(clusterDetailsItem, r));
       }),
     ).then(this.toObjectsByEntityResponse);