refactor(core): refactor WrappedValue (angular#20997)

- Improve `WrappedValue` by adding `unwrap` symetrical to `wrap`.
- remove dead code - `ValueUnwrapper`

The property `wrapped` is an implementation details and should never be accessed
directly - use `unwrap(wrappedValue)`. Will change to protected in Angular 7.

PR Close angular#20997

Author: vicb

packages/core/src/change_detection/change_detection.ts

@@ -12,7 +12,7 @@ import {IterableDifferFactory, IterableDiffers} from './differs/iterable_differs
 import {KeyValueDifferFactory, KeyValueDiffers} from './differs/keyvalue_differs';
 
 export {SimpleChanges} from '../metadata/lifecycle_hooks';
-export {SimpleChange, ValueUnwrapper, WrappedValue, devModeEqual} from './change_detection_util';
+export {SimpleChange, WrappedValue, devModeEqual} from './change_detection_util';
 export {ChangeDetectorRef} from './change_detector_ref';
 export {ChangeDetectionStrategy, ChangeDetectorStatus, isDefaultChangeDetectionStrategy} from './constants';
 export {DefaultIterableDifferFactory} from './differs/default_iterable_differ';

packages/core/src/change_detection/change_detection_util.ts

@@ -26,10 +26,10 @@ export function devModeEqual(a: any, b: any): boolean {
 
 /**
  * Indicates that the result of a {@link Pipe} transformation has changed even though the
- * reference
- * has not changed.
+ * reference has not changed.
  *
- * The wrapped value will be unwrapped by change detection, and the unwrapped value will be stored.
+ * Wrapped values are unwrapped automatically during the change detection, and the unwrapped value
+ * is stored.
  *
  * Example:
  *
@@ -44,26 +44,22 @@ export function devModeEqual(a: any, b: any): boolean {
  * @stable
  */
 export class WrappedValue {
-  constructor(public wrapped: any) {}
+  /** @deprecated from 5.3, use `unwrap()` instead - will switch to protected */
+  wrapped: any;
 
-  static wrap(value: any): WrappedValue { return new WrappedValue(value); }
-}
+  constructor(value: any) { this.wrapped = value; }
 
-/**
- * Helper class for unwrapping WrappedValue s
- */
-export class ValueUnwrapper {
-  public hasWrappedValue = false;
+  /** Creates a wrapped value. */
+  static wrap(value: any): WrappedValue { return new WrappedValue(value); }
 
-  unwrap(value: any): any {
-    if (value instanceof WrappedValue) {
-      this.hasWrappedValue = true;
-      return value.wrapped;
-    }
-    return value;
-  }
+  /**
+   * Returns the underlying value of a wrapped value.
+   * Returns the given `value` when it is not wrapped.
+   **/
+  static unwrap(value: any): any { return WrappedValue.isWrapped(value) ? value.wrapped : value; }
 
-  reset() { this.hasWrappedValue = false; }
+  /** Returns true if `value` is a wrapped value. */
+  static isWrapped(value: any): value is WrappedValue { return value instanceof WrappedValue; }
 }
 
 /**

packages/core/src/core_private_export.ts

@@ -8,7 +8,7 @@
 
 export {ALLOW_MULTIPLE_PLATFORMS as ɵALLOW_MULTIPLE_PLATFORMS} from './application_ref';
 export {APP_ID_RANDOM_PROVIDER as ɵAPP_ID_RANDOM_PROVIDER} from './application_tokens';
-export {ValueUnwrapper as ɵValueUnwrapper, devModeEqual as ɵdevModeEqual} from './change_detection/change_detection_util';
+export {devModeEqual as ɵdevModeEqual} from './change_detection/change_detection_util';
 export {isListLikeIterable as ɵisListLikeIterable} from './change_detection/change_detection_util';
 export {ChangeDetectorStatus as ɵChangeDetectorStatus, isDefaultChangeDetectionStrategy as ɵisDefaultChangeDetectionStrategy} from './change_detection/constants';
 export {Console as ɵConsole} from './console';

packages/core/src/view/provider.ts

@@ -437,10 +437,7 @@ function updateProp(
   providerData.instance[propName] = value;
   if (def.flags & NodeFlags.OnChanges) {
     changes = changes || {};
-    let oldValue = view.oldValues[def.bindingIndex + bindingIdx];
-    if (oldValue instanceof WrappedValue) {
-      oldValue = oldValue.wrapped;
-    }
+    const oldValue = WrappedValue.unwrap(view.oldValues[def.bindingIndex + bindingIdx]);
     const binding = def.bindings[bindingIdx];
     changes[binding.nonMinifiedName !] =
         new SimpleChange(oldValue, value, (view.state & ViewState.FirstCheck) !== 0);

packages/core/src/view/util.ts

@@ -28,13 +28,10 @@ export function tokenKey(token: any): string {
 }
 
 export function unwrapValue(view: ViewData, nodeIdx: number, bindingIdx: number, value: any): any {
-  if (value instanceof WrappedValue) {
-    value = value.wrapped;
-    let globalBindingIdx = view.def.nodes[nodeIdx].bindingIndex + bindingIdx;
-    let oldValue = view.oldValues[globalBindingIdx];
-    if (oldValue instanceof WrappedValue) {
-      oldValue = oldValue.wrapped;
-    }
+  if (WrappedValue.isWrapped(value)) {
+    value = WrappedValue.unwrap(value);
+    const globalBindingIdx = view.def.nodes[nodeIdx].bindingIndex + bindingIdx;
+    const oldValue = WrappedValue.unwrap(view.oldValues[globalBindingIdx]);
     view.oldValues[globalBindingIdx] = new WrappedValue(oldValue);
   }
   return value;

tools/public_api_guard/core/core.d.ts

@@ -1093,8 +1093,10 @@ export declare abstract class ViewRef extends ChangeDetectorRef {
 
 /** @stable */
 export declare class WrappedValue {
-    wrapped: any;
-    constructor(wrapped: any);
+    /** @deprecated */ wrapped: any;
+    constructor(value: any);
+    static isWrapped(value: any): value is WrappedValue;
+    static unwrap(value: any): any;
     static wrap(value: any): WrappedValue;
 }