fix(v1): fresh install failing due to <> syntax

https://github.com/facebook/docusaurus/issues/3199 (#3213)

packages/docusaurus-1.x/.eslintrc.js

@@ -28,6 +28,7 @@ module.exports = {
     'no-plusplus': OFF,
     'prefer-template': OFF,
     'import/no-extraneous-dependencies': OFF,
+    'react/jsx-fragments': OFF, // Babylon v6 does not support <> fragments
     'react/jsx-closing-bracket-location': OFF, // Formatting is left to Prettier.
     'react/jsx-filename-extension': OFF, // Enable in future when migrating.
     'react/jsx-one-expression-per-line': OFF, // Formatting is left to Prettier.

packages/docusaurus-1.x/examples/basics/pages/en/users.js

@@ -34,14 +34,14 @@ class Users extends React.Component {
             </div>
             <div className="logos">{showcase}</div>
             {siteConfig.repoUrl && (
-              <>
+              <React.Fragment>
                 <p>Are you using this project?</p>
                 <a
                   href={`${siteConfig.repoUrl}/edit/master/website/siteConfig.js`}
                   className="button">
                   Add your company
                 </a>
-              </>
+              </React.Fragment>
             )}
           </div>
         </Container>

packages/docusaurus-1.x/lib/start-server.js

@@ -49,6 +49,6 @@ program
   .parse(process.argv);
 
 startDocusaurus().catch((ex) => {
-  console.error(chalk.red(`Failed to start Docusaurus server: ${ex}`));
+  console.error(chalk.red(ex && ex.stack ? ex.stack : ex));
   process.exit(1);
 });

packages/docusaurus-1.x/lib/write-translations.js

@@ -55,6 +55,17 @@ if (fs.existsSync(`${CWD}/data/custom-translation-strings.json`)) {
   );
 }
 
+function parseJSXFile(file) {
+  try {
+    return babylon.parse(fs.readFileSync(file, 'utf8'), {
+      plugins: ['jsx'],
+    });
+  } catch (e) {
+    throw new Error(`Babylon parsing failure for file=${file}: ${e.message}
+    \nNote: Docusaurus v1 currently uses Babylon v6, and <> fragment syntax is not supported`);
+  }
+}
+
 function writeFileAndCreateFolder(file, content) {
   mkdirp.sync(file.replace(new RegExp('/[^/]*$'), ''));
   fs.writeFileSync(file, content);
@@ -151,9 +162,7 @@ function execute() {
   glob.sync(`${CWD}/pages/en/**`).forEach((file) => {
     const extension = nodePath.extname(file);
     if (extension === '.js') {
-      const ast = babylon.parse(fs.readFileSync(file, 'utf8'), {
-        plugins: ['jsx'],
-      });
+      const ast = parseJSXFile(file);
       traverse(ast, {
         enter(path) {
           if (