packages/core: split alerting functionality out from ErrorApiForwarder into ErrorAlerter

docs/getting-started/utility-apis.md

@@ -55,15 +55,16 @@ import {
   errorApiRef,
   AlertApiForwarder,
   ErrorApiForwarder,
+  ErrorAlerter,
 } from '@backstage/core';
 
 const builder = ApiRegistry.builder();
 
 // The alert API is a self-contained implementation that shows alerts to the user.
-builder.add(alertApiRef, new AlertApiForwarder());
+const alertApi = builder.add(alertApiRef, new AlertApiForwarder());
 
 // The error API uses the alert API to send error notifications to the user.
-builder.add(errorApiRef, new ErrorApiForwarder(alertApiForwarder));
+builder.add(errorApiRef, new ErrorAlerter(alertApi, new ErrorApiForwarder()));
 
 const app = createApp({
   apis: apiBuilder.build(),

packages/app/src/apis.ts

@@ -21,6 +21,7 @@ import {
   errorApiRef,
   AlertApiForwarder,
   ErrorApiForwarder,
+  ErrorAlerter,
   featureFlagsApiRef,
   FeatureFlags,
   GoogleAuth,
@@ -40,11 +41,9 @@ import { CircleCIApi, circleCIApiRef } from '@backstage/plugin-circleci';
 
 const builder = ApiRegistry.builder();
 
-export const alertApiForwarder = new AlertApiForwarder();
-builder.add(alertApiRef, alertApiForwarder);
+const alertApi = builder.add(alertApiRef, new AlertApiForwarder());
 
-export const errorApiForwarder = new ErrorApiForwarder(alertApiForwarder);
-builder.add(errorApiRef, errorApiForwarder);
+builder.add(errorApiRef, new ErrorAlerter(alertApi, new ErrorApiForwarder()));
 builder.add(circleCIApiRef, new CircleCIApi());
 builder.add(featureFlagsApiRef, new FeatureFlags());
 

packages/core/src/api/apis/implementations/ErrorAlerter.ts

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 { ErrorApi, ErrorContext, AlertApi } from '../../../';
+
+/**
+ * Decorates an ErrorApi by also forwarding error messages
+ * to the alertApi with an 'error' severity.
+ */
+export class ErrorAlerter implements ErrorApi {
+  constructor(
+    private readonly alertApi: AlertApi,
+    private readonly errorApi: ErrorApi,
+  ) {}
+
+  post(error: Error, context?: ErrorContext) {
+    if (!context?.hidden) {
+      this.alertApi.post({ message: error.message, severity: 'error' });
+    }
+
+    return this.errorApi.post(error, context);
+  }
+
+  error$() {
+    return this.errorApi.error$();
+  }
+}

packages/core/src/api/apis/implementations/ErrorApiForwarder.ts

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { ErrorApi, ErrorContext, AlertApi } from '../../../';
+import { ErrorApi, ErrorContext } from '../../../';
 import { PublishSubject } from './lib';
 import { Observable } from '../../types';
 
@@ -23,13 +23,7 @@ export class ErrorApiForwarder implements ErrorApi {
     context?: ErrorContext;
   }>();
 
-  constructor(private readonly alertApi: AlertApi) {}
-
   post(error: Error, context?: ErrorContext) {
-    if (!context?.hidden) {
-      this.alertApi.post({ message: error.message, severity: 'error' });
-    }
-
     this.subject.next({ error, context });
   }
 

packages/core/src/api/apis/implementations/index.ts

@@ -21,5 +21,6 @@
 export * from './auth';
 export * from './AppThemeSelector';
 export * from './AlertApiForwarder';
+export * from './ErrorAlerter';
 export * from './ErrorApiForwarder';
 export * from './OAuthRequestManager';