fix: should try package exports first per spec

fixtures/prefer-file-over-dir/package.json

@@ -0,0 +1,3 @@
+{
+  "name": "prefer-file-over-dir"
+}

src/lib.rs

@@ -781,13 +781,6 @@ impl<C: Cache<Cp = FsCachedPath>> ResolverGeneric<C> {
                 //    may have a @scope/ prefix and the subpath begins with a slash (`/`).
                 if !package_name.is_empty() {
                     let cached_path = cached_path.normalize_with(package_name, self.cache.as_ref());
-                    // file is preferred over directory when specifier doesn't contains a slash which indicates a dir
-                    // node_modules/bar.js vs node_modules/bar/index.js
-                    if !specifier.contains('/') {
-                        if let Some(path) = self.load_as_file(&cached_path, ctx)? {
-                            return Ok(Some(path));
-                        }
-                    }
                     // Try foo/node_modules/package_name
                     if self.cache.is_dir(&cached_path, ctx) {
                         // a. LOAD_PACKAGE_EXPORTS(X, DIR)
@@ -823,6 +816,19 @@ impl<C: Cache<Cp = FsCachedPath>> ResolverGeneric<C> {
                 if self.options.resolve_to_context {
                     return Ok(self.cache.is_dir(&cached_path, ctx).then(|| cached_path.clone()));
                 }
+
+                if self.options.alias_fields.is_empty() && self.cache.is_file(&cached_path, ctx) {
+                    return Ok(Some(cached_path));
+                }
+
+                // `is_file` could be false because no extensions are considered yet,
+                // so we need to try `load_as_file` first when `specifier` does not end with a slash which indicates a dir instead.
+                if !specifier.ends_with('/') {
+                    if let Some(path) = self.load_as_file(&cached_path, ctx)? {
+                        return Ok(Some(path));
+                    }
+                }
+
                 if self.cache.is_dir(&cached_path, ctx) {
                     if let Some(path) = self.load_browser_field_or_alias(&cached_path, ctx)? {
                         return Ok(Some(path));
@@ -831,9 +837,7 @@ impl<C: Cache<Cp = FsCachedPath>> ResolverGeneric<C> {
                         return Ok(Some(path));
                     }
                 }
-                if let Some(path) = self.load_as_file(&cached_path, ctx)? {
-                    return Ok(Some(path));
-                }
+
                 if let Some(path) = self.load_as_directory(&cached_path, ctx)? {
                     return Ok(Some(path));
                 }

src/tests/resolve.rs

@@ -119,12 +119,17 @@ fn resolve_hash_as_module() {
 }
 
 #[test]
-fn prefer_file_over_pkg() {
-    let f = super::fixture_root();
-    let fixture = f.join("prefer-file-over-pkg");
+fn prefer_file_over_dir() {
+    let f = super::fixture_root().join("prefer-file-over-dir");
     let resolver = Resolver::default();
-    let resolved_path = resolver.resolve(fixture.clone(), "bar").map(|r| r.full_path());
-    assert_eq!(resolved_path, Ok(fixture.join("node_modules/bar.js")));
+    let data = [
+        ("one level package name", f.clone(), "bar", f.join("node_modules/bar.js")),
+        ("scoped level package name", f.clone(), "@foo/bar", f.join("node_modules/@foo/bar.js")),
+    ];
+    for (comment, path, request, expected) in data {
+        let resolved_path = resolver.resolve(&path, request).map(|r| r.full_path());
+        assert_eq!(resolved_path, Ok(expected), "{comment} {path:?} {request}");
+    }
 }
 
 #[cfg(windows)]