chore: don't use Object.assign (#1791)

Author: jelbourn

src/lib/core/util/object-extend.spec.ts

@@ -0,0 +1,50 @@
+import {extendObject} from './object-extend';
+
+
+describe('extendObject', () => {
+  it('should extend an object', () => {
+    let extended = extendObject({}, {x: 123});
+
+    expect(extended).toEqual({x: 123});
+  });
+
+  it('should overwrite existing properties', () => {
+    let extended = extendObject({x: 456}, {x: 123});
+
+    expect(extended).toEqual({x: 123});
+  });
+
+  it('should add additional properties', () => {
+    let extended = extendObject({x: 456}, {y: 123});
+
+    expect(extended).toEqual({x: 456, y: 123});
+  });
+
+  it('should extend from multiple sources', () => {
+    let extended = extendObject({}, {x: 123}, {y: 456});
+
+    expect(extended).toEqual({x: 123, y: 456});
+  });
+
+  it('should overwrite properties from the later source', () => {
+    let extended = extendObject({}, {x: 123}, {x: 456});
+
+    expect(extended).toEqual({x: 456});
+  });
+
+  it('should treat null and undefined sources as empty objects', () => {
+    let extended = extendObject({}, null, {x: 123}, undefined, {y: 456});
+
+    expect(extended).toEqual({x: 123, y: 456});
+  });
+
+  it('should throw an error when the dest object is null', () => {
+    expect(() => extendObject(null, {x: 123}))
+        .toThrowError('Cannot convert undefined or null to object');
+  });
+
+  it('should throw an error when the dest object is undefined', () => {
+    expect(() => extendObject(undefined, {x: 123}))
+        .toThrowError('Cannot convert undefined or null to object');
+  });
+});

src/lib/core/util/object-extend.ts

@@ -0,0 +1,24 @@
+/**
+ * Extends an object with the *enumerable* and *own* properties of one or more source objects,
+ * similar to Object.assign.
+ *
+ * @param dest The object which will have properties copied to it.
+ * @param sources The source objects from which properties will be copied.
+ */
+export function extendObject(dest: any, ...sources: any[]): any {
+  if (dest == null) {
+    throw TypeError('Cannot convert undefined or null to object');
+  }
+
+  for (let source of sources) {
+    if (source != null) {
+      for (let key in source) {
+        if (source.hasOwnProperty(key)) {
+          dest[key] = source[key];
+        }
+      }
+    }
+  }
+
+  return dest;
+}

src/lib/dialog/dialog.ts

@@ -14,6 +14,7 @@ import {MdDialogRef} from './dialog-ref';
 import {DialogInjector} from './dialog-injector';
 import {MdDialogContainer} from './dialog-container';
 import {A11yModule, InteractivityChecker} from '../core';
+import {extendObject} from '../core/util/object-extend';
 
 export {MdDialogConfig} from './dialog-config';
 export {MdDialogRef} from './dialog-ref';
@@ -41,7 +42,7 @@ export class MdDialog {
    * @param config
    */
   open<T>(component: ComponentType<T>, config?: MdDialogConfig): MdDialogRef<T> {
-    config = this._applyConfigDefaults(config);
+    config = _applyConfigDefaults(config);
 
     let overlayRef = this._createOverlay(config);
     let dialogContainer = this._attachDialogContainer(overlayRef, config);
@@ -127,15 +128,15 @@ export class MdDialog {
 
     return state;
   }
+}
 
-  /**
-   * Applies default options to the dialog config.
-   * @param dialogConfig Config to be modified.
-   * @returns The new configuration object.
-   */
-  private _applyConfigDefaults(dialogConfig: MdDialogConfig): MdDialogConfig {
-    return Object.assign(new MdDialogConfig(), dialogConfig);
-  }
+/**
+ * Applies default options to the dialog config.
+ * @param dialogConfig Config to be modified.
+ * @returns The new configuration object.
+ */
+function _applyConfigDefaults(dialogConfig: MdDialogConfig): MdDialogConfig {
+  return extendObject(new MdDialogConfig(), dialogConfig);
 }
 
 

src/lib/snack-bar/snack-bar.ts

@@ -20,6 +20,7 @@ import {MdSnackBarConfig} from './snack-bar-config';
 import {MdSnackBarRef} from './snack-bar-ref';
 import {MdSnackBarContainer} from './snack-bar-container';
 import {SimpleSnackBar} from './simple-snack-bar';
+import {extendObject} from '../core/util/object-extend';
 
 // TODO(josephperrott): Automate dismiss after timeout.
 
@@ -124,7 +125,7 @@ export class MdSnackBar {
  * @returns The new configuration object with defaults applied.
  */
 function _applyConfigDefaults(config: MdSnackBarConfig): MdSnackBarConfig {
-  return Object.assign(new MdSnackBarConfig(), config);
+  return extendObject(new MdSnackBarConfig(), config);
 }