add app-next-example-plugin

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: Johan Haals <johan.haals@gmail.com>
Co-authored-by: Philipp Hugenroth <philipph@spotify.com>
Co-authored-by: Camila Belo <camilaibs@gmail.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/app-next-example-plugin/.eslintrc.js

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+module.exports = require('@backstage/cli/config/eslint-factory')(__dirname);

packages/app-next-example-plugin/package.json

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+{
+  "name": "@backstage/app-next-example-plugin",
+  "description": "Backstage internal example plugin",
+  "version": "0.0.0",
+  "publishConfig": {
+    "access": "public",
+    "main": "dist/index.esm.js",
+    "types": "dist/index.d.ts"
+  },
+  "private": true,
+  "backstage": {
+    "role": "frontend-plugin"
+  },
+  "homepage": "https://backstage.io",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/backstage/backstage",
+    "directory": "packages/app-next-example-plugin"
+  },
+  "keywords": [
+    "backstage"
+  ],
+  "license": "Apache-2.0",
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "scripts": {
+    "build": "backstage-cli package build",
+    "start": "backstage-cli package start",
+    "lint": "backstage-cli package lint",
+    "test": "backstage-cli package test",
+    "prepack": "backstage-cli package prepack",
+    "postpack": "backstage-cli package postpack",
+    "clean": "backstage-cli package clean"
+  },
+  "dependencies": {
+    "@backstage/frontend-plugin-api": "workspace:^",
+    "@backstage/core-components": "workspace:^",
+    "@material-ui/icons": "^4.9.1"
+  },
+  "peerDependencies": {
+    "react": "^16.13.1 || ^17.0.0",
+    "react-dom": "^16.13.1 || ^17.0.0",
+    "react-router-dom": "6.0.0-beta.0 || ^6.3.0"
+  },
+  "devDependencies": {
+    "@backstage/cli": "workspace:^",
+    "cross-fetch": "^3.1.5",
+    "msw": "^1.0.0"
+  },
+  "files": [
+    "dist"
+  ]
+}

packages/app-next-example-plugin/src/Component.tsx

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+/*
+ * 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 React from 'react';
+
+export const Component = () => (
+  <div>
+    <h1>Winning</h1>
+  </div>
+);

packages/app-next-example-plugin/src/ExampleSidebarItem.tsx

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+/*
+ * 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 React from 'react';
+import { SidebarItem } from '@backstage/core-components';
+import SaveIcon from '@material-ui/icons/Save';
+
+export const ExampleSidebarItem = () => (
+  <SidebarItem text="Example" to="/example" icon={SaveIcon} />
+);

packages/app-next-example-plugin/src/plugin.tsx

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+/*
+ * 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 {
+  createPageExtension,
+  createPlugin,
+} from '@backstage/frontend-plugin-api';
+import { Component } from './Component';
+
+export const ExamplePage = createPageExtension({
+  id: 'example.page',
+  defaultPath: '/example',
+  component: () => () => Component,
+});
+
+export const examplePlugin = createPlugin({
+  id: 'example',
+  extensions: [ExamplePage],
+});