BackendPluginManager use default exports

for dynamic plugins on the new backend system.

This allows making a plugin dynamic without any source code change
(which was previously required to add a dedicated entrypoint).

Signed-off-by: David Festal <dfestal@redhat.com>

packages/backend-plugin-manager/src/loader/CommonJSModuleLoader.ts

@@ -49,6 +49,6 @@ export class CommonJSModuleLoader implements ModuleLoader {
   }
 
   async load(packagePath: string): Promise<any> {
-    return await import(/* webpackIgnore: true */ packagePath);
+    return await require(/* webpackIgnore: true */ packagePath);
   }
 }

packages/backend-plugin-manager/src/manager/plugin-manager.test.ts

@@ -113,6 +113,94 @@ describe('backend-plugin-manager', () => {
           >([]);
         },
       },
+      {
+        name: 'should successfully load a new backend plugin by the default BackendFeature',
+        packageManifest: {
+          name: 'backend-dynamic-plugin-test',
+          version: '0.0.0',
+          backstage: {
+            role: 'backend-plugin',
+          },
+          main: 'dist/index.cjs.js',
+        },
+        indexFile: {
+          retativePath: ['dist', 'index.cjs.js'],
+          content: `const alpha = { $$type: '@backstage/BackendFeature' }; exports["default"] = alpha;`,
+        },
+        expectedLogs(location) {
+          return {
+            infos: [
+              {
+                message: `loaded dynamic backend plugin 'backend-dynamic-plugin-test' from '${location}'`,
+              },
+            ],
+          };
+        },
+        checkLoadedPlugins(plugins) {
+          expect(plugins).toMatchObject([
+            {
+              name: 'backend-dynamic-plugin-test',
+              version: '0.0.0',
+              role: 'backend-plugin',
+              platform: 'node',
+              installer: {
+                kind: 'new',
+              },
+            },
+          ]);
+          const installer: NewBackendPluginInstaller = (
+            plugins[0] as BackendDynamicPlugin
+          ).installer as NewBackendPluginInstaller;
+          expect(installer.install()).toEqual<
+            BackendFeature | BackendFeature[]
+          >({ $$type: '@backstage/BackendFeature' });
+        },
+      },
+      {
+        name: 'should successfully load a new backend plugin by the default BackendFeatureFactory',
+        packageManifest: {
+          name: 'backend-dynamic-plugin-test',
+          version: '0.0.0',
+          backstage: {
+            role: 'backend-plugin',
+          },
+          main: 'dist/index.cjs.js',
+        },
+        indexFile: {
+          retativePath: ['dist', 'index.cjs.js'],
+          content: `const alpha = () => { return { $$type: '@backstage/BackendFeature' } };
+             alpha.$$type = '@backstage/BackendFeatureFactory';
+             exports["default"] = alpha;`,
+        },
+        expectedLogs(location) {
+          return {
+            infos: [
+              {
+                message: `loaded dynamic backend plugin 'backend-dynamic-plugin-test' from '${location}'`,
+              },
+            ],
+          };
+        },
+        checkLoadedPlugins(plugins) {
+          expect(plugins).toMatchObject([
+            {
+              name: 'backend-dynamic-plugin-test',
+              version: '0.0.0',
+              role: 'backend-plugin',
+              platform: 'node',
+              installer: {
+                kind: 'new',
+              },
+            },
+          ]);
+          const installer: NewBackendPluginInstaller = (
+            plugins[0] as BackendDynamicPlugin
+          ).installer as NewBackendPluginInstaller;
+          expect(installer.install()).toEqual<
+            BackendFeature | BackendFeature[]
+          >({ $$type: '@backstage/BackendFeature' });
+        },
+      },
       {
         name: 'should successfully load a new backend plugin module',
         packageManifest: {
@@ -221,7 +309,7 @@ describe('backend-plugin-manager', () => {
           return {
             errors: [
               {
-                message: `dynamic backend plugin 'backend-dynamic-plugin-test' could not be loaded from '${location}': the module should export a 'const dynamicPluginInstaller: BackendDynamicPluginInstaller' field.`,
+                message: `dynamic backend plugin 'backend-dynamic-plugin-test' could not be loaded from '${location}': the module should either export a 'BackendFeature' or 'BackendFeatureFactory' as default export, or export a 'const dynamicPluginInstaller: BackendDynamicPluginInstaller' field as dynamic loading entrypoint.`,
               },
             ],
           };
@@ -249,7 +337,7 @@ describe('backend-plugin-manager', () => {
           return {
             errors: [
               {
-                message: `dynamic backend plugin 'backend-dynamic-plugin-test' could not be loaded from '${location}': the module should export a 'const dynamicPluginInstaller: BackendDynamicPluginInstaller' field.`,
+                message: `dynamic backend plugin 'backend-dynamic-plugin-test' could not be loaded from '${location}': the module should either export a 'BackendFeature' or 'BackendFeatureFactory' as default export, or export a 'const dynamicPluginInstaller: BackendDynamicPluginInstaller' field as dynamic loading entrypoint.`,
               },
             ],
           };
@@ -378,7 +466,7 @@ describe('backend-plugin-manager', () => {
         logger,
         async bootstrap(_: string, __: string[]): Promise<void> {},
         load: async (packagePath: string) =>
-          await import(/* webpackIgnore: true */ packagePath),
+          await require(/* webpackIgnore: true */ packagePath),
       });
 
       const loadedPlugins: DynamicPlugin[] = await pluginManager.loadPlugins();

packages/backend-plugin-manager/src/manager/plugin-manager.ts

@@ -140,12 +140,25 @@ export class PluginManager implements BackendPluginProvider {
       `${plugin.location}/${plugin.manifest.main}`,
     );
     try {
-      const { dynamicPluginInstaller } = await this.moduleLoader.load(
-        packagePath,
-      );
+      const pluginModule = await this.moduleLoader.load(packagePath);
+
+      let dynamicPluginInstaller;
+      if (isBackendFeature(pluginModule.default)) {
+        dynamicPluginInstaller = {
+          kind: 'new',
+          install: () => pluginModule.default,
+        };
+      } else if (isBackendFeatureFactory(pluginModule.default)) {
+        dynamicPluginInstaller = {
+          kind: 'new',
+          install: pluginModule.default,
+        };
+      } else {
+        dynamicPluginInstaller = pluginModule.dynamicPluginInstaller;
+      }
       if (!isBackendDynamicPluginInstaller(dynamicPluginInstaller)) {
         this.logger.error(
-          `dynamic backend plugin '${plugin.manifest.name}' could not be loaded from '${plugin.location}': the module should export a 'const dynamicPluginInstaller: BackendDynamicPluginInstaller' field.`,
+          `dynamic backend plugin '${plugin.manifest.name}' could not be loaded from '${plugin.location}': the module should either export a 'BackendFeature' or 'BackendFeatureFactory' as default export, or export a 'const dynamicPluginInstaller: BackendDynamicPluginInstaller' field as dynamic loading entrypoint.`,
         );
         return undefined;
       }
@@ -263,3 +276,21 @@ export const dynamicPluginsFeatureDiscoveryServiceFactory =
       return new DynamicPluginsEnabledFeatureDiscoveryService(dynamicPlugins);
     },
   });
+
+function isBackendFeature(value: unknown): value is BackendFeature {
+  return (
+    !!value &&
+    typeof value === 'object' &&
+    (value as BackendFeature).$$type === '@backstage/BackendFeature'
+  );
+}
+
+function isBackendFeatureFactory(
+  value: unknown,
+): value is () => BackendFeature {
+  return (
+    !!value &&
+    typeof value === 'function' &&
+    (value as any).$$type === '@backstage/BackendFeatureFactory'
+  );
+}