fix(common): throw an error if trackBy is not a function

modules/@angular/common/src/directives/ng_for.ts

@@ -89,9 +89,18 @@ export class NgForRow {
 @Directive({selector: '[ngFor][ngForOf]'})
 export class NgFor implements DoCheck, OnChanges {
   @Input() ngForOf: any;
-  @Input() ngForTrackBy: TrackByFn;
+  @Input()
+  set ngForTrackBy(fn: TrackByFn) {
+    if (typeof fn !== 'function') {
+      throw new Error(`trackBy must be a function, but received ${JSON.stringify(fn)}`);
+    }
+    this._trackByFn = fn;
+  }
+
+  get ngForTrackBy(): TrackByFn { return this._trackByFn; }
 
   private _differ: IterableDiffer = null;
+  private _trackByFn: TrackByFn;
 
   constructor(
       private _viewContainer: ViewContainerRef, private _template: TemplateRef<NgForRow>,
@@ -119,7 +128,7 @@ export class NgFor implements DoCheck, OnChanges {
     }
   }
 
-  ngDoCheck() {
+  ngDoCheck(): void {
     if (this._differ) {
       const changes = this._differ.diff(this.ngForOf);
       if (changes) this._applyChanges(changes);

modules/@angular/common/test/directives/ng_for_spec.ts

@@ -294,6 +294,16 @@ export function main() {
        }));
 
     describe('track by', () => {
+      it('should throw if trackBy is not a function', async(() => {
+           const template =
+               `<template ngFor let-item [ngForOf]="items" [ngForTrackBy]="item?.id"></template>`;
+           fixture = createTestComponent(template);
+
+           getComponent().items = [{id: 1}, {id: 2}];
+           expect(() => fixture.detectChanges())
+               .toThrowError(/trackBy must be a function, but received null/);
+         }));
+
       it('should set the context to the component instance', async(() => {
            const template =
                `<template ngFor let-item [ngForOf]="items" [ngForTrackBy]="trackByContext.bind(this)"></template>`;

modules/@angular/platform-browser/src/browser/browser_adapter.ts

@@ -67,7 +67,7 @@ const _chromeNumKeyPadMap = {
  * @security Tread carefully! Interacting with the DOM directly is dangerous and
  * can introduce XSS risks.
  */
-/* tslint:disable:requireParameterType */
+/* tslint:disable:requireParameterType no-console */
 export class BrowserDomAdapter extends GenericBrowserDomAdapter {
   parse(templateHtml: string) { throw new Error('parse not implemented'); }
   static makeCurrent() { setRootDomAdapter(new BrowserDomAdapter()); }
@@ -89,7 +89,6 @@ export class BrowserDomAdapter extends GenericBrowserDomAdapter {
 
   log(error: string): void {
     if (window.console) {
-      // tslint:disable-next-line:no-console
       window.console.log && window.console.log(error);
     }
   }