add plugin id format warning on frontend framework

Signed-off-by: Juan Pablo Garcia Ripa <sarabadu@gmail.com>

packages/frontend-plugin-api/src/wiring/constants.ts

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2025 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.
+ */
+
+// NOTE: changing any of these constants need to be reflected in
+// @backstage/backend-plugin-api/src/wiring/constants.ts as well
+
+/**
+ * The pattern that IDs must match.
+ *
+ * @remarks
+ * ids must only contain the letters `a` through `z` and digits, in groups separated by
+ * dashes. Additionally, the very first character of the first group
+ * must be a letter, not a digit
+ *
+ * @public
+ */
+export const ID_PATTERN = /^[a-z][a-z0-9]*(?:-[a-z0-9]+)*$/i;

packages/frontend-plugin-api/src/wiring/createFrontendPlugin.ts

@@ -30,6 +30,7 @@ import { FeatureFlagConfig } from './types';
 import { MakeSortedExtensionsMap } from './MakeSortedExtensionsMap';
 import { JsonObject } from '@backstage/types';
 import { RouteRef, SubRouteRef, ExternalRouteRef } from '../routing';
+import { ID_PATTERN } from './constants';
 
 /**
  * Information about the plugin.
@@ -199,6 +200,13 @@ export function createFrontendPlugin<
 > {
   const pluginId = options.pluginId;
 
+  if (!ID_PATTERN.test(pluginId)) {
+    // eslint-disable-next-line no-console
+    console.warn(
+      `WARNING: The pluginId '${pluginId}' will be invalid soon, please change it to match the pattern ${ID_PATTERN} (letters, digits, and dashes only, starting with a letter)`,
+    );
+  }
+
   const extensions = new Array<Extension<any>>();
   const extensionDefinitionsById = new Map<
     string,