enhance(normalizr): Avoid hidden class mutation in normalize() result (#3878)

The normalize() return object was constructed with result: '' as any,
then mutated via ret.result = visit(...). This causes a V8 hidden class
transition when the property type changes from string to the actual
result type (array/object/string), triggering "field type constness
changed" invalidations that deoptimize code depending on this object
shape.

Restructured to compute the result first and construct the final
NormalizedSchema in a single step, keeping the object shape stable from
creation.

Made-with: Cursor

Author: ntucker

.changeset/normalize-hidden-class.md

@@ -0,0 +1,7 @@
+---
+'@data-client/normalizr': patch
+---
+
+Avoid hidden class mutation in normalize() return object
+
+The normalize result object was constructed with `result: '' as any` then mutated via `ret.result = visit(...)`, causing a V8 hidden class transition when the property type changed from string to the actual result type. Restructured to compute the result first and construct the final object in a single step.

packages/normalizr/src/normalize/normalize.ts

@@ -79,15 +79,18 @@ See https://dataclient.io/rest/api/RestEndpoint#parseResponse for more informati
     }
   }
 
-  const ret: NormalizedSchema<E, R> = {
-    result: '' as any,
+  const state = {
     entities: { ...entities },
     indexes: { ...indexes },
     entitiesMeta: { ...entitiesMeta },
   };
-  const visit = getVisit(new NormalizeDelegate(ret, meta));
-  ret.result = visit(schema, input, input, undefined, args);
-  return ret;
+  const visit = getVisit(new NormalizeDelegate(state, meta));
+  return {
+    result: visit(schema, input, input, undefined, args) as any as R,
+    entities: state.entities as any,
+    indexes: state.indexes as any,
+    entitiesMeta: state.entitiesMeta as any,
+  };
 };
 
 function expectedSchemaType(schema: Schema) {