fix: resolve mathjs error when using extensionAlias

fixtures/pnpm/package.json

@@ -6,6 +6,8 @@
     "axios": "1.6.2",
     "ipaddr.js": "2.2.0",
     "postcss": "8.4.33",
-    "styled-components": "6.1.1"
+    "styled-components": "6.1.1",
+    "mathjs": "13.2.0",
+    "decimal.js": "10.4.3"
   }
 }

src/lib.rs

@@ -1050,22 +1050,23 @@ impl<Fs: FileSystem> ResolverGeneric<Fs> {
         let path = cached_path.path();
         let Some(filename) = path.file_name() else { return Ok(None) };
         let path_without_extension = path.with_extension("");
+
         ctx.with_fully_specified(true);
         for extension in extensions {
             let mut path_with_extension = path_without_extension.clone().into_os_string();
             path_with_extension.reserve_exact(extension.len());
             path_with_extension.push(extension);
             let cached_path = self.cache.value(Path::new(&path_with_extension));
-            // Bail if path is module directory such as `ipaddr.js`
-            if cached_path.is_dir(&self.cache.fs, ctx) {
-                ctx.with_fully_specified(false);
-                return Ok(None);
-            }
             if let Some(path) = self.load_alias_or_file(&cached_path, ctx)? {
                 ctx.with_fully_specified(false);
                 return Ok(Some(path));
             }
         }
+        // Bail if path is module directory such as `ipaddr.js`
+        if !cached_path.is_file(&self.cache.fs, ctx) {
+            ctx.with_fully_specified(false);
+            return Ok(None);
+        }
         // Create a meaningful error message.
         let dir = path.parent().unwrap().to_path_buf();
         let filename_without_extension = Path::new(filename).with_extension("");

tests/resolve_test.rs

@@ -130,3 +130,57 @@ fn ipaddr_js() {
         assert_eq!(resolution, Ok(module_path.clone()));
     }
 }
+
+#[test]
+fn decimal_js() {
+    let dir = dir();
+    let path = dir.join("fixtures/pnpm");
+    let module_path =
+        dir.join("node_modules/.pnpm/[email protected]/node_modules/decimal.js/decimal.mjs");
+
+    let resolvers = [
+        // with `extension_alias`
+        Resolver::new(ResolveOptions {
+            extension_alias: vec![(".js".into(), vec![".js".into(), ".ts".into(), ".tsx".into()])],
+            condition_names: vec!["import".into()],
+            ..ResolveOptions::default()
+        }),
+        // default
+        Resolver::new(ResolveOptions {
+            condition_names: vec!["import".into()],
+            ..ResolveOptions::default()
+        }),
+    ];
+
+    for resolver in resolvers {
+        let resolution = resolver.resolve(&path, "decimal.js").map(|r| r.full_path());
+        assert_eq!(resolution, Ok(module_path.clone()));
+    }
+}
+
+#[test]
+fn decimal_js_from_mathjs() {
+    let dir = dir();
+    let path = dir.join("node_modules/.pnpm/[email protected]/node_modules/mathjs/lib/esm");
+    let module_path =
+        dir.join("node_modules/.pnpm/[email protected]/node_modules/decimal.js/decimal.mjs");
+
+    let resolvers = [
+        // with `extension_alias`
+        Resolver::new(ResolveOptions {
+            extension_alias: vec![(".js".into(), vec![".js".into(), ".ts".into(), ".tsx".into()])],
+            condition_names: vec!["import".into()],
+            ..ResolveOptions::default()
+        }),
+        // default
+        Resolver::new(ResolveOptions {
+            condition_names: vec!["import".into()],
+            ..ResolveOptions::default()
+        }),
+    ];
+
+    for resolver in resolvers {
+        let resolution = resolver.resolve(&path, "decimal.js").map(|r| r.full_path());
+        assert_eq!(resolution, Ok(module_path.clone()));
+    }
+}