[Enhancement]: private change detection

src/-private/change.ts

@@ -1,9 +1,21 @@
-import { IChange } from '../types';
+/* import { IChange } from '../types'; */
 
-export default class Change implements IChange {
-  value: any;
+const VALUE = Symbol('__value__');
 
-  constructor(value: any) {
-    this.value = value;
+export default class Change {
+  [VALUE]: unknown;
+
+  constructor(value: unknown) {
+    this[VALUE] = value;
+  }
+}
+
+// TODO: not sure why this function type guard isn't working
+export const isChange = (maybeChange: unknown): maybeChange is Change =>
+  VALUE in (maybeChange as any);
+
+export function getChangeValue(maybeChange: Change | unknown): any {
+  if (isChange(maybeChange)) {
+    return maybeChange[VALUE];
   }
 }

src/index.ts

@@ -1,4 +1,4 @@
-import Change from './-private/change';
+import Change, { getChangeValue, isChange } from './-private/change';
 import { getKeyValues, getKeyErrorValues } from './utils/get-key-values';
 import lookupValidator from './utils/validator-lookup';
 import { notifierForEvent } from './-private/evented';
@@ -946,8 +946,8 @@ export class BufferedChangeset implements IChangeset {
         }
 
         if (this.isObject(result)) {
-          if (result instanceof Change) {
-            return result.value;
+          if (isChange(result)) {
+            return getChangeValue(result);
           }
 
           const baseContent = this.safeGet(content, baseKey);
@@ -962,8 +962,8 @@ export class BufferedChangeset implements IChangeset {
       }
 
       // this comes after the isObject check to ensure we don't lose remaining keys
-      if (baseChanges instanceof Change && remaining.length === 0) {
-        return baseChanges.value;
+      if (isChange(baseChanges) && remaining.length === 0) {
+        return getChangeValue(baseChanges.value);
       }
     }
 

src/types/index.ts

@@ -60,11 +60,12 @@ export type ValidatorMap =
   | null
   | undefined;
 
-export interface IChange {
-  value: any;
-}
+// https://github.com/microsoft/TypeScript/pull/26797
+/* export interface IChange { */
+/*   [s: symbol]: any; */
+/* } */
 export interface Changes {
-  [s: string]: IChange;
+  [s: string]: any; //IChange;
 }
 
 export interface Content {

src/utils/get-deep.ts

@@ -1,4 +1,4 @@
-import Change from '../-private/change';
+import { isChange } from '../-private/change';
 
 /**
  * Handles both single key or nested string keys ('person.name')
@@ -47,7 +47,7 @@ export function getSubObject<T extends Record<string, any>>(root: T, path: strin
       return undefined;
     }
 
-    if (obj[parts[i]] instanceof Change) {
+    if (isChange(obj[parts[i]])) {
       obj = obj[parts[i]].value;
     } else {
       obj = obj[parts[i]];

src/utils/has-changes.ts

@@ -1,9 +1,9 @@
 import isObject from './is-object';
-import Change from '../-private/change';
+import { isChange } from '../-private/change';
 
 export function hasChanges(changes: Record<string, any>): boolean {
   for (let key in changes) {
-    if (changes[key] instanceof Change) {
+    if (isChange(changes[key])) {
       return true;
     }
 

src/utils/has-key.ts

@@ -1,4 +1,4 @@
-import Change from '../-private/change';
+import { isChange } from '../-private/change';
 
 export function hasKey(record: Record<string, any>, path: string, safeGet: Function): boolean {
   const keys = path.split('.');
@@ -20,7 +20,7 @@ export function pathInChanges(
   path: string,
   safeGet: Function
 ): boolean {
-  if (record instanceof Change) {
+  if (isChange(record)) {
     return false;
   }
 
@@ -32,7 +32,7 @@ export function pathInChanges(
       return false;
     }
 
-    if (keys[keys.length - 1] !== key && safeGet(obj, key) instanceof Change) {
+    if (keys[keys.length - 1] !== key && isChange(safeGet(obj, key))) {
       return true;
     }
 

src/utils/merge-deep.ts

@@ -1,4 +1,4 @@
-import Change from '../-private/change';
+import Change, { getChangeValue, isChange } from '../-private/change';
 import normalizeObject from './normalize-object';
 
 interface Options {
@@ -63,8 +63,8 @@ function buildPathToValue(
 ): Record<string, any> {
   Object.keys(source).forEach((key: string): void => {
     let possible = source[key];
-    if (possible && possible.hasOwnProperty('value') && possible instanceof Change) {
-      kv[[...possibleKeys, key].join('.')] = possible.value;
+    if (possible && isChange(possible)) {
+      kv[[...possibleKeys, key].join('.')] = getChangeValue(possible);
       return;
     }
 
@@ -105,7 +105,7 @@ function mergeTargetAndSource(target: any, source: any, options: Options): any {
     if (
       propertyIsOnObject(target, key) &&
       isMergeableObject(source[key]) &&
-      !(source[key] instanceof Change)
+      !isChange(source[key])
     ) {
       options.safeSet(
         target,
@@ -114,8 +114,8 @@ function mergeTargetAndSource(target: any, source: any, options: Options): any {
       );
     } else {
       let next = source[key];
-      if (next && next instanceof Change) {
-        return options.safeSet(target, key, next.value);
+      if (next && isChange(next)) {
+        return options.safeSet(target, key, getChangeValue(next));
       }
 
       return options.safeSet(target, key, normalizeObject(next));

src/utils/normalize-object.ts

@@ -1,4 +1,4 @@
-import Change from '../-private/change';
+import { getChangeValue, isChange } from '../-private/change';
 import isObject from './is-object';
 
 /**
@@ -30,17 +30,17 @@ export default function normalizeObject<T extends { [key: string]: any }>(
     return target;
   }
 
-  if (target instanceof Change) {
-    return target.value;
+  if (isChange(target)) {
+    return getChangeValue(target.value);
   }
 
   let obj = { ...target };
 
   for (let key in obj) {
     const next: any = obj[key];
     if (next && isObj(next)) {
-      if (Object.prototype.hasOwnProperty.call(next, 'value') && next instanceof Change) {
-        obj[key] = next.value;
+      if (isChange(next)) {
+        obj[key] = getChangeValue(next);
       } else {
         try {
           JSON.stringify(next);

src/utils/object-tree-node.ts

@@ -1,7 +1,7 @@
 import { ProxyHandler, Content } from '../types';
 import isObject from './is-object';
 import setDeep from './set-deep';
-import Change from '../-private/change';
+import Change, { getChangeValue, isChange } from '../-private/change';
 import normalizeObject from './normalize-object';
 
 const objectProxyHandler = {
@@ -23,8 +23,8 @@ const objectProxyHandler = {
       }
     }
 
-    if (childValue instanceof Change) {
-      return childValue.value;
+    if (isChange(childValue)) {
+      return getChangeValue(childValue);
     }
 
     if (isObject(childValue)) {

src/utils/set-deep.ts

@@ -1,4 +1,4 @@
-import Change from '../-private/change';
+import Change, { getChangeValue, isChange } from '../-private/change';
 import isObject from './is-object';
 
 interface Options {
@@ -62,11 +62,11 @@ export default function setDeep(
     const isObj = isObject(target[prop]);
     if (!isObj) {
       options.safeSet(target, prop, {});
-    } else if (isObj && target[prop] instanceof Change) {
-      if (isObject(target[prop].value)) {
+    } else if (isObj && isChange(target[prop])) {
+      if (isObject(getChangeValue(target[prop]))) {
         // if an object, we don't want to lose sibling keys
         const siblings = findSiblings(target[prop].value, keys);
-        const resolvedValue = value instanceof Change ? value.value : value;
+        const resolvedValue = isChange(value) ? getChangeValue(value) : value;
         target[prop] = new Change(
           setDeep(siblings, keys.slice(1, keys.length).join('.'), resolvedValue, options)
         );