core-compat-api: initial stab at plugin conversion

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/core-compat-api/package.json

@@ -34,7 +34,8 @@
     "@backstage/core-plugin-api": "workspace:^",
     "@backstage/frontend-plugin-api": "workspace:^",
     "@backstage/version-bridge": "workspace:^",
-    "@types/react": "^16.13.1 || ^17.0.0"
+    "@types/react": "^16.13.1 || ^17.0.0",
+    "lodash": "^4.17.21"
   },
   "devDependencies": {
     "@backstage-community/plugin-puppetdb": "^0.1.18",

packages/core-compat-api/src/convertLegacyPlugin.tsx

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2024 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 as LegacyBackstagePlugin,
+  getComponentData,
+  RouteRef as LegacyRouteRef,
+} from '@backstage/core-plugin-api';
+import {
+  ExtensionDefinition,
+  BackstagePlugin as NewBackstagePlugin,
+  createPageExtension,
+  createPlugin,
+} from '@backstage/frontend-plugin-api';
+import kebabCase from 'lodash/kebabCase';
+import {
+  convertLegacyRouteRef,
+  convertLegacyRouteRefs,
+} from './convertLegacyRouteRef';
+import { ComponentType } from 'react';
+import React from 'react';
+import { compatWrapper } from './compatWrapper';
+
+/** @internal */
+export function convertLegacyExtension(
+  LegacyExtension: ComponentType<{}>,
+  legacyPlugin: LegacyBackstagePlugin,
+): ExtensionDefinition<any, any> {
+  const element = <LegacyExtension />;
+
+  const plugin = getComponentData<LegacyBackstagePlugin>(
+    element,
+    'core.plugin',
+  );
+  if (legacyPlugin !== plugin) {
+    throw new Error(
+      `The extension does not belong to the same plugin, got ${plugin?.getId()}`,
+    );
+  }
+
+  const name = getComponentData<string>(element, 'core.extensionName');
+  if (!name) {
+    throw new Error('Extension has no name');
+  }
+
+  const mountPoint = getComponentData<LegacyRouteRef>(
+    element,
+    'core.mountPoint',
+  );
+
+  if (name.endsWith('Page')) {
+    return createPageExtension({
+      defaultPath: kebabCase(name.slice(0, -'Page'.length)),
+      routeRef: mountPoint && convertLegacyRouteRef(mountPoint),
+      loader: () => Promise.resolve(compatWrapper(element)),
+    });
+  }
+}
+
+/** @public */
+export function convertLegacyPlugin(
+  legacyPlugin: LegacyBackstagePlugin,
+  options: { extensions: ExtensionDefinition<any, any>[] },
+): NewBackstagePlugin {
+  return createPlugin({
+    id: legacyPlugin.getId(),
+    featureFlags: [...legacyPlugin.getFeatureFlags()],
+    routes: convertLegacyRouteRefs(legacyPlugin.routes ?? {}),
+    externalRoutes: convertLegacyRouteRefs(legacyPlugin.externalRoutes ?? {}),
+    extensions: options.extensions,
+  });
+}

yarn.lock

@@ -4202,6 +4202,7 @@ __metadata:
     "@testing-library/jest-dom": ^6.0.0
     "@testing-library/react": ^15.0.0
     "@types/react": ^16.13.1 || ^17.0.0
+    lodash: ^4.17.21
   peerDependencies:
     react: ^16.13.1 || ^17.0.0 || ^18.0.0
     react-router-dom: 6.0.0-beta.0 || ^6.3.0