tools: make doctool work if no internet available

Allow doctool to fallback to use local files if not building a release
build.

PR-URL: #30214
Fixes: #29918
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>

tools/doc/versions.js

@@ -1,21 +1,33 @@
 'use strict';
 
+const { readFileSync } = require('fs');
+const path = require('path');
+const srcRoot = path.join(__dirname, '..', '..');
+
 let _versions;
 
+const isRelease = () => {
+  const re = /#define NODE_VERSION_IS_RELEASE 0/;
+  const file = path.join(srcRoot, 'src', 'node_version.h');
+  return !re.test(readFileSync(file, { encoding: 'utf8' }));
+};
+
 const getUrl = (url) => {
   return new Promise((resolve, reject) => {
     const https = require('https');
-    const request = https.get(url, (response) => {
+    const request = https.get(url, { timeout: 5000 }, (response) => {
       if (response.statusCode !== 200) {
         reject(new Error(
           `Failed to get ${url}, status code ${response.statusCode}`));
       }
       response.setEncoding('utf8');
       let body = '';
+      response.on('aborted', () => reject());
       response.on('data', (data) => body += data);
       response.on('end', () => resolve(body));
     });
     request.on('error', (err) => reject(err));
+    request.on('timeout', () => request.abort());
   });
 };
 
@@ -27,10 +39,23 @@ module.exports = {
 
     // The CHANGELOG.md on release branches may not reference newer semver
     // majors of Node.js so fetch and parse the version from the master branch.
-    const githubContentUrl = 'https://raw.githubusercontent.com/nodejs/node/';
-    const changelog = await getUrl(`${githubContentUrl}/master/CHANGELOG.md`);
+    const url =
+      'https://raw.githubusercontent.com/nodejs/node/master/CHANGELOG.md';
+    let changelog;
+    try {
+      changelog = await getUrl(url);
+    } catch (e) {
+      // Fail if this is a release build, otherwise fallback to local files.
+      if (isRelease()) {
+        throw e;
+      } else {
+        const file = path.join(srcRoot, 'CHANGELOG.md');
+        console.warn(`Unable to retrieve ${url}. Falling back to ${file}.`);
+        changelog = readFileSync(file, { encoding: 'utf8' });
+      }
+    }
     const ltsRE = /Long Term Support/i;
-    const versionRE = /\* \[Node\.js ([0-9.]+)\][^-—]+[-—]\s*(.*)\n/g;
+    const versionRE = /\* \[Node\.js ([0-9.]+)\][^-—]+[-—]\s*(.*)\r?\n/g;
     _versions = [];
     let match;
     while ((match = versionRE.exec(changelog)) != null) {