🐛 keep toString always return original value for function in sandbox (#1785)

* fix: correct toString for functions

* Update src/sandbox/common.ts

* Update src/sandbox/common.ts

* handle getter in toString descriptor

* toString function predict

Co-authored-by: Kuitos <kuitos.lau@gmail.com>

src/sandbox/__tests__/common.test.ts

@@ -59,4 +59,24 @@ describe('getTargetValue', () => {
     const boundFn = getTargetValue(window, callableFunction);
     expect(boundFn.prototype).toBe(callableFunction.prototype);
   });
+
+  it("should work well while function's toString()'s return value keeps the same as the origin", () => {
+    function callableFunction1() {}
+    function callableFunction2() {}
+    function callableFunction3() {}
+    callableFunction2.toString = () => 'instance toString';
+    Object.defineProperty(callableFunction3, 'toString', {
+      get() {
+        return () => 'instance toString';
+      },
+    });
+
+    const boundFn1 = getTargetValue(window, callableFunction1);
+    const boundFn2 = getTargetValue(window, callableFunction2);
+    const boundFn3 = getTargetValue(window, callableFunction3);
+
+    expect(boundFn1.toString()).toBe(callableFunction1.toString());
+    expect(boundFn2.toString()).toBe(callableFunction2.toString());
+    expect(boundFn3.toString()).toBe(callableFunction3.toString());
+  });
 });

src/sandbox/common.ts

@@ -51,6 +51,25 @@ export function getTargetValue(target: any, value: any): any {
       Object.defineProperty(boundValue, 'prototype', { value: value.prototype, enumerable: false, writable: true });
     }
 
+    // Some util, like `function isNative() {  return typeof Ctor === 'function' && /native code/.test(Ctor.toString()) }` relies on the original `toString()` result
+    // but bound functions will always return "function() {[native code]}" for `toString`, which is misleading
+    if (typeof value.toString === 'function') {
+      const valueHasInstanceToString = value.hasOwnProperty('toString') && !boundValue.hasOwnProperty('toString');
+      const boundValueHasPrototypeToString = boundValue.toString === Function.prototype.toString;
+
+      if (valueHasInstanceToString || boundValueHasPrototypeToString) {
+        const originToStringDescriptor = Object.getOwnPropertyDescriptor(
+          valueHasInstanceToString ? value : Function.prototype,
+          'toString',
+        );
+
+        Object.defineProperty(boundValue, 'toString', {
+          ...originToStringDescriptor,
+          ...(originToStringDescriptor?.get ? null : { value: () => value.toString() }),
+        });
+      }
+    }
+
     functionBoundedValueMap.set(value, boundValue);
     return boundValue;
   }