fix(es/modules): Preserve extensions (#4524)

crates/swc/tests/fixture/issues-3xxx/3576/input/.swcrc

@@ -0,0 +1,17 @@
+{
+    "jsc": {
+        "baseUrl": "./src",
+        "paths": {
+            "@modules/*": [
+                "./modules/*"
+            ]
+        },
+        "target": "es2020",
+        "parser": {
+            "syntax": "typescript"
+        }
+    },
+    "module": {
+        "type": "es6"
+    }
+}

crates/swc/tests/fixture/issues-3xxx/3576/input/src/input.ts

@@ -0,0 +1,5 @@
+// We keep the .js extension for ESModules, but SWC will strip it:
+import { modulo } from "@modules/modulo.js";
+import { sum } from "./sum.js";
+
+console.log(modulo(sum(1, 2), 2));

crates/swc/tests/fixture/issues-3xxx/3576/output/src/input.ts

@@ -0,0 +1,4 @@
+// We keep the .js extension for ESModules, but SWC will strip it:
+import { modulo } from "./modules/modulo.js";
+import { sum } from "./sum.js";
+console.log(modulo(sum(1, 2), 2));

crates/swc_ecma_loader/src/resolvers/node.rs

@@ -55,9 +55,7 @@ fn find_package_root(path: &Path) -> Option<PathBuf> {
     None
 }
 
-pub fn to_absolute_path(path: impl AsRef<Path>) -> Result<PathBuf, Error> {
-    let path = path.as_ref();
-
+pub fn to_absolute_path(path: &Path) -> Result<PathBuf, Error> {
     let absolute_path = if path.is_absolute() {
         path.to_path_buf()
     } else {

crates/swc_ecma_transforms_module/src/path.rs

@@ -100,9 +100,9 @@ where
     R: Resolve,
 {
     fn resolve_import(&self, base: &FileName, module_specifier: &str) -> Result<JsWord, Error> {
-        fn to_specifier(target_path: &str, is_file: Option<bool>) -> JsWord {
+        fn to_specifier(target_path: &str, is_file: Option<bool>, had_speicifer: bool) -> JsWord {
             let mut p = PathBuf::from(target_path);
-            if is_file.unwrap_or_else(|| p.is_file()) {
+            if !had_speicifer && is_file.unwrap_or_else(|| p.is_file()) {
                 if let Some(v) = p.extension() {
                     if v == "ts" || v == "tsx" || v == "js" || v == "jsx" {
                         p.set_extension("");
@@ -130,6 +130,12 @@ where
             debug!("invoking resolver");
         }
 
+        let had_speicifer = module_specifier
+            .split('/')
+            .last()
+            .map(|s| s.contains('.'))
+            .unwrap_or(false);
+
         let target = self.resolver.resolve(base, module_specifier);
         let target = match target {
             Ok(v) => v,
@@ -141,7 +147,7 @@ where
 
         let target = match target {
             FileName::Real(v) => v,
-            FileName::Custom(s) => return Ok(to_specifier(&s, None)),
+            FileName::Custom(s) => return Ok(to_specifier(&s, None, had_speicifer)),
             _ => {
                 unreachable!(
                     "Node path provider does not support using `{:?}` as a target file name",
@@ -178,7 +184,13 @@ where
 
         let rel_path = match rel_path {
             Some(v) => v,
-            None => return Ok(to_specifier(&target.display().to_string(), Some(is_file))),
+            None => {
+                return Ok(to_specifier(
+                    &target.display().to_string(),
+                    Some(is_file),
+                    had_speicifer,
+                ))
+            }
         };
 
         {
@@ -215,9 +227,13 @@ where
             Cow::Owned(format!("./{}", s))
         };
         if cfg!(target_os = "windows") {
-            Ok(to_specifier(&s.replace('\\', "/"), Some(is_file)))
+            Ok(to_specifier(
+                &s.replace('\\', "/"),
+                Some(is_file),
+                had_speicifer,
+            ))
         } else {
-            Ok(to_specifier(&s, Some(is_file)))
+            Ok(to_specifier(&s, Some(is_file), had_speicifer))
         }
     }
 }