fix API reference + add regression test

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

scripts/verify-api-reference.js

@@ -0,0 +1,39 @@
+#!/usr/bin/env node
+/*
+ * Copyright 2020 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.
+ */
+
+/* eslint-disable import/no-extraneous-dependencies */
+
+const { resolve: resolvePath } = require('path');
+const { promises: fs } = require('fs');
+
+async function main() {
+  const indexContent = await fs.readFile(
+    resolvePath(__dirname, '../docs/reference/index.md'),
+    'utf8',
+  );
+
+  if (!indexContent.includes('types used within Backstage')) {
+    throw new Error(
+      'Could not find package documentation for @backstage/types in the API reference index',
+    );
+  }
+}
+
+main().catch(error => {
+  console.error(error.stack);
+  process.exit(1);
+});