Turbopack: allow shadowing the require global in ESM (vercel#70453)

Closes PACK-3275

Among other things, a regression from
vercel#70255, but it could also happen
with `__dirname`.

To prevent `SyntaxError: Identifier 'require' has already been declared`

turbopack/crates/turbopack-ecmascript/src/chunk/item.rs

@@ -141,6 +141,8 @@ impl EcmascriptChunkItemContent {
         if this.options.async_module.is_some() {
             code += "__turbopack_async_module__(async (__turbopack_handle_async_dependencies__, \
                      __turbopack_async_result__) => { try {\n";
+        } else {
+            code += "{\n";
         }
 
         code.push_source(&this.inner_code, this.source_map);
@@ -152,6 +154,8 @@ impl EcmascriptChunkItemContent {
                  }}, {});",
                 opts.has_top_level_await
             )?;
+        } else {
+            code += "}";
         }
 
         code += "})";

turbopack/crates/turbopack-tests/tests/execution/turbopack/code-gen/esm-declare-globals/input/index.js

@@ -0,0 +1,11 @@
+import './module.js'
+
+const require = () => 'result'
+const __dirname = 'something'
+const __filename = 'something/else'
+
+it('should allow declaring CJS globals in ESM', () => {
+  expect(require()).toBe('result')
+  expect(__dirname).toBe('something')
+  expect(__filename).toBe('something/else')
+})