docs: add basic script to verify local documentation links

docs/verify-links.js

@@ -0,0 +1,89 @@
+#!/usr/bin/env node
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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.
+ */
+
+const { resolve: resolvePath, dirname } = require('path');
+const fs = require('fs-extra');
+const fetch = require('node-fetch');
+const recursive = require('recursive-readdir');
+
+const projectRoot = resolvePath(__dirname, '..');
+
+async function verifyUrl(basePath, url) {
+  url = url.replace(/#.*$/, '');
+  url = url.replace(
+    /https:\/\/github.com\/spotify\/backstage\/(tree|blob)\/master/,
+    '',
+  );
+  if (!url) {
+    return;
+  }
+
+  // Only verify existence of local files for now, so skip anything with a schema
+  if (!url.match(/[a-z]+:/)) {
+    const path = url.startsWith('/')
+      ? resolvePath(projectRoot, `.${url}`)
+      : resolvePath(dirname(resolvePath(projectRoot, basePath)), url);
+    const exists = await fs.pathExists(path);
+    if (!exists) {
+      return { url, basePath };
+    }
+  }
+
+  return;
+}
+
+async function verifyFile(filePath) {
+  const content = await fs.readFile(filePath, 'utf8');
+  const mdLinks = content.match(/\[.+?\]\(.+?\)/g) || [];
+  const badUrls = [];
+
+  for (const mdLink of mdLinks) {
+    const url = mdLink.match(/\[.+\]\((.+)\)/)[1].trim();
+    const badUrl = await verifyUrl(filePath, url);
+    if (badUrl) {
+      badUrls.push(badUrl);
+    }
+  }
+
+  return badUrls;
+}
+
+async function main() {
+  process.chdir(projectRoot);
+
+  const files = await recursive('.', ['node_modules', 'dist', 'bin']);
+  const mdFiles = files.filter(f => f.endsWith('.md'));
+  const badUrls = [];
+
+  for (const mdFile of mdFiles) {
+    const badFileUrls = await verifyFile(mdFile);
+    badUrls.push(...badFileUrls);
+  }
+
+  if (badUrls.length) {
+    console.log(`Found ${badUrls.length} bad links within repo`);
+    for (const { url, basePath } of badUrls) {
+      console.error(`Unable to reach ${url}, linked from ${basePath}`);
+    }
+    process.exit(1);
+  }
+}
+
+main().catch(error => {
+  console.error(error.stack);
+  process.exit(1);
+});