fix(transform-imports): Transform side-effect imports (#473)

Closes: #474

---

[Original issue](#329):
Imports with side effects were being incorrectly removed. The expected
behavior is to retain the import and apply the transformation.

The current behavior causes issues when the code includes TypeScript
side-effect imports. These are skipped by the plugin and remain
untransformed, which leads to runtime failures in Node.js (since it
cannot import .ts files directly).

Author: jsbravoc

.changeset/old-papayas-destroy.md

@@ -0,0 +1,5 @@
+---
+"@swc/plugin-transform-imports": patch
+---
+
+fix(transform-imports): Transform side-effect imports

packages/transform-imports/__tests__/__snapshots__/wasm.test.ts.snap

@@ -63,7 +63,7 @@ export { default as Footer } from "my-library/components/App/Footer";
 `;
 
 exports[`Should load transform-imports wasm plugin correctly > Should transform side-effect-imports correctly 1`] = `
-"import './upload/upload.ts';
+"import './upload/upload.js';
 import './scripts/scripts.model.js';
 "
 `;

packages/transform-imports/transform/src/lib.rs

@@ -381,9 +381,25 @@ impl VisitMut for TransformImports<'_> {
         for item in module.body.take() {
             match item {
                 ModuleItem::ModuleDecl(ModuleDecl::Import(decl)) => {
-                    // Ignore side-effect only imports
                     if decl.specifiers.is_empty() {
-                        new_items.push(ModuleItem::ModuleDecl(ModuleDecl::Import(decl)));
+                        if let Some(rewriter) = self.should_rewrite(&decl.src.value) {
+                            let new_path = rewriter.new_path(None);
+                            let raw_with_quotes = Atom::from(format!("'{}'", new_path.as_ref()));
+                            let new_src = Box::new(Str {
+                                span: decl.src.span,
+                                value: new_path.clone(),
+                                raw: Some(raw_with_quotes),
+                            });
+                            let new_decl = ImportDecl {
+                                src: new_src,
+                                specifiers: vec![],
+                                ..decl
+                            };
+
+                            new_items.push(ModuleItem::ModuleDecl(ModuleDecl::Import(new_decl)));
+                        } else {
+                            new_items.push(ModuleItem::ModuleDecl(ModuleDecl::Import(decl)));
+                        }
                         continue;
                     }
 

packages/transform-imports/transform/tests/fixture/side-effect-imports/output.js

@@ -1,2 +1,2 @@
-import './upload/upload.ts';
+import './upload/upload.js';
 import './scripts/scripts.model.js';