refactor[devtools]: forbid editing class instances in props (#26522)

## Summary
Fixes https://github.com/facebook/react/issues/24781

Restricting from editing props, which are class instances, because their
internals should be opaque.

Proposed changes:
1. Adding new data type `class_instance`: based on prototype chain of an
object we will check if its plain or not. If not, then will be marked as
`class_instance`. This should not affect `arrays`, ..., because we do
this in the end of an `object` case in `getDataType` function.

Important detail: this approach won't work for objects created with
`Object.create`, because of the custom prototype. This can also be
bypassed by manually deleting a prototype ¯\\\_(ツ)_/¯
I am not sure if there might be a better solution (which will cover all
cases) to detect if object is a class instance. Initially I was trying
to use `Object.getPrototypeOf(object) === Object.prototype`, but this
won't work for cases when we are dealing with `iframe`.


2. Objects with a type `class_instance` will be marked as unserializable
and read-only.

## Demo
`person` is a class instance, `object` is a plain object


https://user-images.githubusercontent.com/28902667/228914791-ebdc8ab0-eb5c-426d-8163-66d56b5e8790.mov

fixtures/devtools/standalone/index.html

@@ -334,6 +334,11 @@
         },
       });
 
+      class Foo {
+        flag = false;
+        object = {a: {b: {c: {d: 1}}}}
+      }
+
       function UnserializableProps() {
         return (
           <ChildComponent
@@ -343,6 +348,7 @@
             setOfSets={setOfSets}
             typedArray={typedArray}
             immutable={immutable}
+            classInstance={new Foo()}
           />
         );
       }

packages/react-devtools-shared/src/__tests__/utils-test.js

@@ -10,6 +10,7 @@
 import {
   getDisplayName,
   getDisplayNameForReactElement,
+  isPlainObject,
 } from 'react-devtools-shared/src/utils';
 import {stackToComponentSources} from 'react-devtools-shared/src/devtools/utils';
 import {
@@ -270,4 +271,30 @@ describe('utils', () => {
       expect(gte('10.0.0', '9.0.0')).toBe(true);
     });
   });
+
+  describe('isPlainObject', () => {
+    it('should return true for plain objects', () => {
+      expect(isPlainObject({})).toBe(true);
+      expect(isPlainObject({a: 1})).toBe(true);
+      expect(isPlainObject({a: {b: {c: 123}}})).toBe(true);
+    });
+
+    it('should return false if object is a class instance', () => {
+      expect(isPlainObject(new (class C {})())).toBe(false);
+    });
+
+    it('should retun false for objects, which have not only Object in its prototype chain', () => {
+      expect(isPlainObject([])).toBe(false);
+      expect(isPlainObject(Symbol())).toBe(false);
+    });
+
+    it('should retun false for primitives', () => {
+      expect(isPlainObject(5)).toBe(false);
+      expect(isPlainObject(true)).toBe(false);
+    });
+
+    it('should return true for objects with no prototype', () => {
+      expect(isPlainObject(Object.create(null))).toBe(true);
+    });
+  });
 });

packages/react-devtools-shared/src/hydration.js

@@ -52,7 +52,7 @@ export type Unserializable = {
   size?: number,
   type: string,
   unserializable: boolean,
-  ...
+  [string | number]: any,
 };
 
 // This threshold determines the depth at which the bridge "dehydrates" nested data.
@@ -248,7 +248,6 @@ export function dehydrate(
         // Other types (e.g. typed arrays, Sets) will not spread correctly.
         Array.from(data).forEach(
           (item, i) =>
-            // $FlowFixMe[prop-missing] Unserializable doesn't have an index signature
             (unserializableValue[i] = dehydrate(
               item,
               cleaned,
@@ -296,6 +295,7 @@ export function dehydrate(
 
     case 'object':
       isPathAllowedCheck = isPathAllowed(path);
+
       if (level >= LEVEL_THRESHOLD && !isPathAllowedCheck) {
         return createDehydrated(type, true, data, cleaned, path);
       } else {
@@ -316,15 +316,46 @@ export function dehydrate(
         return object;
       }
 
+    case 'class_instance':
+      isPathAllowedCheck = isPathAllowed(path);
+
+      if (level >= LEVEL_THRESHOLD && !isPathAllowedCheck) {
+        return createDehydrated(type, true, data, cleaned, path);
+      }
+
+      const value: Unserializable = {
+        unserializable: true,
+        type,
+        readonly: true,
+        preview_short: formatDataForPreview(data, false),
+        preview_long: formatDataForPreview(data, true),
+        name: data.constructor.name,
+      };
+
+      getAllEnumerableKeys(data).forEach(key => {
+        const keyAsString = key.toString();
+
+        value[keyAsString] = dehydrate(
+          data[key],
+          cleaned,
+          unserializable,
+          path.concat([keyAsString]),
+          isPathAllowed,
+          isPathAllowedCheck ? 1 : level + 1,
+        );
+      });
+
+      unserializable.push(path);
+
+      return value;
+
     case 'infinity':
     case 'nan':
     case 'undefined':
       // Some values are lossy when sent through a WebSocket.
       // We dehydrate+rehydrate them to preserve their type.
       cleaned.push(path);
-      return {
-        type,
-      };
+      return {type};
 
     default:
       return data;

packages/react-devtools-shared/src/utils.js

@@ -534,6 +534,7 @@ export type DataType =
   | 'array_buffer'
   | 'bigint'
   | 'boolean'
+  | 'class_instance'
   | 'data_view'
   | 'date'
   | 'function'
@@ -620,6 +621,11 @@ export function getDataType(data: Object): DataType {
           return 'html_all_collection';
         }
       }
+
+      if (!isPlainObject(data)) {
+        return 'class_instance';
+      }
+
       return 'object';
     case 'string':
       return 'string';
@@ -835,6 +841,8 @@ export function formatDataForPreview(
     }
     case 'date':
       return data.toString();
+    case 'class_instance':
+      return data.constructor.name;
     case 'object':
       if (showFormattedValue) {
         const keys = Array.from(getAllEnumerableKeys(data)).sort(alphaSortKeys);
@@ -873,3 +881,12 @@ export function formatDataForPreview(
       }
   }
 }
+
+// Basically checking that the object only has Object in its prototype chain
+export const isPlainObject = (object: Object): boolean => {
+  const objectPrototype = Object.getPrototypeOf(object);
+  if (!objectPrototype) return true;
+
+  const objectParentPrototype = Object.getPrototypeOf(objectPrototype);
+  return !objectParentPrototype;
+};

packages/react-devtools-shell/src/app/InspectableElements/UnserializableProps.js

@@ -33,6 +33,13 @@ const immutable = Immutable.fromJS({
 });
 const bigInt = BigInt(123); // eslint-disable-line no-undef
 
+class Foo {
+  flag = false;
+  object: Object = {
+    a: {b: {c: {d: 1}}},
+  };
+}
+
 export default function UnserializableProps(): React.Node {
   return (
     <ChildComponent
@@ -45,6 +52,7 @@ export default function UnserializableProps(): React.Node {
       typedArray={typedArray}
       immutable={immutable}
       bigInt={bigInt}
+      classInstance={new Foo()}
     />
   );
 }