perf: skip searching for package.json when alias_fields is not provided (#194)

perf: omit searching for package.json when `alias_fields` is not provided

Author: Boshen

src/lib.rs

@@ -647,11 +647,15 @@ impl<Fs: FileSystem> ResolverGeneric<Fs> {
     }
 
     fn load_alias_or_file(&self, cached_path: &CachedPath, ctx: &mut Ctx) -> ResolveResult {
-        if let Some(package_json) =
-            cached_path.find_package_json(&self.cache.fs, &self.options, ctx)?
-        {
-            if let Some(path) = self.load_browser_field(cached_path, None, &package_json, ctx)? {
-                return Ok(Some(path));
+        if !self.options.alias_fields.is_empty() {
+            if let Some(package_json) =
+                cached_path.find_package_json(&self.cache.fs, &self.options, ctx)?
+            {
+                if let Some(path) =
+                    self.load_browser_field(cached_path, None, &package_json, ctx)?
+                {
+                    return Ok(Some(path));
+                }
             }
         }
         // enhanced-resolve: try file as alias

src/tests/incorrect_description_file.rs

@@ -17,8 +17,11 @@ fn incorrect_description_file_1() {
         column: 0,
     });
     assert_eq!(resolution, Err(error));
-    assert_eq!(ctx.file_dependencies, FxHashSet::from_iter([f.join("pack1/package.json")]));
-    assert!(ctx.missing_dependencies.is_empty());
+    assert_eq!(
+        ctx.file_dependencies,
+        FxHashSet::from_iter([f.join("pack1"), f.join("pack1/package.json")])
+    );
+    assert!(!ctx.missing_dependencies.is_empty());
 }
 
 // should not resolve main in incorrect description file #2