frontend-app-api: fix circular dependency

Signed-off-by: Vincenzo Scamporlino <vincenzos@spotify.com>

packages/frontend-app-api/api-report.md

@@ -27,7 +27,7 @@ export type AppRouteBinder = <
 ) => void;
 
 // @public (undocumented)
-export function createApp(options?: {
+export function createApp(options: {
   features?: (BackstagePlugin | ExtensionOverrides)[];
   configLoader?: () => Promise<ConfigApi>;
   bindRoutes?(context: { bind: AppRouteBinder }): void;

packages/frontend-app-api/src/routing/extractRouteInfoFromAppNode.ts

@@ -15,10 +15,9 @@
  */
 
 import { RouteRef, coreExtensionData } from '@backstage/frontend-plugin-api';
-// eslint-disable-next-line @backstage/no-relative-monorepo-imports
-import { toLegacyPlugin } from '../wiring/createApp';
 import { BackstageRouteObject } from './types';
 import { AppNode } from '@backstage/frontend-plugin-api';
+import { toLegacyPlugin } from './toLegacyPlugin';
 
 // We always add a child that matches all subroutes but without any route refs. This makes
 // sure that we're always able to match each route no matter how deep the navigation goes.

packages/frontend-app-api/src/routing/toLegacyPlugin.ts

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2023 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 { BackstagePlugin } from '@backstage/frontend-plugin-api';
+import { BackstagePlugin as LegacyBackstagePlugin } from '@backstage/core-plugin-api';
+import { getOrCreateGlobalSingleton } from '@backstage/version-bridge';
+
+// Make sure that we only convert each new plugin instance to its legacy equivalent once
+const legacyPluginStore = getOrCreateGlobalSingleton(
+  'legacy-plugin-compatibility-store',
+  () => new WeakMap<BackstagePlugin, LegacyBackstagePlugin>(),
+);
+
+export function toLegacyPlugin(plugin: BackstagePlugin): LegacyBackstagePlugin {
+  let legacy = legacyPluginStore.get(plugin);
+  if (legacy) {
+    return legacy;
+  }
+
+  const errorMsg = 'Not implemented in legacy plugin compatibility layer';
+  const notImplemented = () => {
+    throw new Error(errorMsg);
+  };
+
+  legacy = {
+    getId(): string {
+      return plugin.id;
+    },
+    get routes() {
+      return {};
+    },
+    get externalRoutes() {
+      return {};
+    },
+    getApis: notImplemented,
+    getFeatureFlags: notImplemented,
+    provide: notImplemented,
+  };
+
+  legacyPluginStore.set(plugin, legacy);
+  return legacy;
+}

packages/frontend-app-api/src/wiring/createApp.tsx

@@ -80,7 +80,6 @@ import { BrowserRouter, Route } from 'react-router-dom';
 import { SidebarItem } from '@backstage/core-components';
 import { DarkTheme, LightTheme } from '../extensions/themes';
 import { extractRouteInfoFromAppNode } from '../routing/extractRouteInfoFromAppNode';
-import { getOrCreateGlobalSingleton } from '@backstage/version-bridge';
 import {
   appLanguageApiRef,
   translationApiRef,
@@ -91,6 +90,7 @@ import { resolveRouteBindings } from '../routing/resolveRouteBindings';
 import { collectRouteIds } from '../routing/collectRouteIds';
 import { createAppTree } from '../tree';
 import { AppNode } from '@backstage/frontend-plugin-api';
+import { toLegacyPlugin } from '../routing/toLegacyPlugin';
 
 const builtinExtensions = [
   Core,
@@ -328,42 +328,6 @@ export function createSpecializedApp(options?: {
   };
 }
 
-// Make sure that we only convert each new plugin instance to its legacy equivalent once
-const legacyPluginStore = getOrCreateGlobalSingleton(
-  'legacy-plugin-compatibility-store',
-  () => new WeakMap<BackstagePlugin, LegacyBackstagePlugin>(),
-);
-
-export function toLegacyPlugin(plugin: BackstagePlugin): LegacyBackstagePlugin {
-  let legacy = legacyPluginStore.get(plugin);
-  if (legacy) {
-    return legacy;
-  }
-
-  const errorMsg = 'Not implemented in legacy plugin compatibility layer';
-  const notImplemented = () => {
-    throw new Error(errorMsg);
-  };
-
-  legacy = {
-    getId(): string {
-      return plugin.id;
-    },
-    get routes() {
-      return {};
-    },
-    get externalRoutes() {
-      return {};
-    },
-    getApis: notImplemented,
-    getFeatureFlags: notImplemented,
-    provide: notImplemented,
-  };
-
-  legacyPluginStore.set(plugin, legacy);
-  return legacy;
-}
-
 function createLegacyAppContext(plugins: BackstagePlugin[]): AppContext {
   return {
     getPlugins(): LegacyBackstagePlugin[] {