fix(v2): swizzle should be able to handle single js file (#1846)

* fix(v2): swizzle should be able to handle single js file

* nits

CHANGELOG-2.x.md

@@ -5,6 +5,7 @@
 - Fix `keywords` frontmatter for SEO not working properly.
 - Fix `swizzle` command not passing context properly to theme packages.
 - Add `extendCli` api for plugins. This will allow plugin to further extend Docusaurus CLI.
+- Fix `swizzle` command not being able to swizzle single js file.
 
 ## 2.0.0-alpha.27
 

packages/docusaurus/src/commands/swizzle.ts

@@ -28,12 +28,18 @@ export async function swizzle(
     if (componentName) {
       fromPath = path.join(fromPath, componentName);
       toPath = path.join(toPath, componentName);
+
+      // Handle single js file only.
+      // E.g: if <fromPath> does not exist, we try to swizzle <fromPath>.js instead
+      if (!fs.existsSync(fromPath) && fs.existsSync(`${fromPath}.js`)) {
+        [fromPath, toPath] = [`${fromPath}.js`, `${toPath}.js`];
+      }
     }
     await fs.copy(fromPath, toPath);
 
     const relativeDir = path.relative(process.cwd(), toPath);
     const fromMsg = chalk.blue(
-      componentName ? `${themeName}/${componentName}` : themeName,
+      componentName ? `${themeName} ${chalk.yellow(componentName)}` : themeName,
     );
     const toMsg = chalk.cyan(relativeDir);
     console.log(