feat(exception_handler): change ExceptionHandler to output context

Author: vsavkin

modules/angular2/src/core/exception_handler.ts

@@ -1,5 +1,5 @@
 import {Injectable} from 'angular2/di';
-import {isPresent, print} from 'angular2/src/facade/lang';
+import {isPresent, print, BaseException} from 'angular2/src/facade/lang';
 import {ListWrapper, isListLikeIterable} from 'angular2/src/facade/collection';
 import {DOM} from 'angular2/src/dom/dom_adapter';
 
@@ -13,30 +13,44 @@ import {DOM} from 'angular2/src/dom/dom_adapter';
  * # Example
  *
  * ```javascript
- * @Component({
- *   selector: 'my-app',
- *   viewInjector: [
- *     bind(ExceptionHandler).toClass(MyExceptionHandler)
- *   ]
- * })
- * @View(...)
- * class MyApp { ... }
- *
  *
  * class MyExceptionHandler implements ExceptionHandler {
  *   call(error, stackTrace = null, reason = null) {
  *     // do something with the exception
  *   }
  * }
  *
+ * bootstrap(MyApp, [bind(ExceptionHandler).toClass(MyExceptionHandler)])
+ *
  * ```
  */
 @Injectable()
 export class ExceptionHandler {
-  call(error: Object, stackTrace: string | List<string> = null, reason: string = null) {
-    var longStackTrace =
-        isListLikeIterable(stackTrace) ? ListWrapper.join(<any>stackTrace, "\n\n") : stackTrace;
-    var reasonStr = isPresent(reason) ? `\n${reason}` : '';
-    DOM.logError(`${error}${reasonStr}\nSTACKTRACE:\n${longStackTrace}`);
+  logError: Function = DOM.logError;
+
+  call(exception: Object, stackTrace: string | string[] = null, reason: string = null) {
+    var longStackTrace = isListLikeIterable(stackTrace) ?
+                             (<any>stackTrace).join("\n\n-----async gap-----\n") :
+                             stackTrace;
+
+    this.logError(`${exception}\n\n${longStackTrace}`);
+
+    if (isPresent(reason)) {
+      this.logError(`Reason: ${reason}`);
+    }
+
+    var context = this._findContext(exception);
+    if (isPresent(context)) {
+      this.logError("Error Context:");
+      this.logError(context);
+    }
+
+    throw exception;
+  }
+
+  _findContext(exception: any): any {
+    if (!(exception instanceof BaseException)) return null;
+    return isPresent(exception.context) ? exception.context :
+                                          this._findContext(exception.originalException);
   }
 }

modules/angular2/test/core/exception_handler_spec.ts

@@ -0,0 +1,90 @@
+import {
+  AsyncTestCompleter,
+  beforeEach,
+  ddescribe,
+  describe,
+  expect,
+  iit,
+  inject,
+  it,
+  xdescribe,
+  xit,
+  IS_DARTIUM,
+  Log
+} from 'angular2/test_lib';
+import {BaseException} from 'angular2/src/facade/lang';
+import {ExceptionHandler} from 'angular2/src/core/exception_handler';
+
+class _CustomException {
+  context = "some context";
+}
+
+export function main() {
+  describe('ExceptionHandler', () => {
+    var log, handler;
+
+    beforeEach(() => {
+      log = new Log();
+      handler = new ExceptionHandler();
+      handler.logError = (e) => log.add(e);
+    });
+
+    it("should output exception", () => {
+      try {
+        handler.call(new BaseException("message!"));
+      } catch (e) {
+      }
+      expect(log.result()).toContain("message!");
+    });
+
+    it("should output stackTrace", () => {
+      try {
+        handler.call(new BaseException("message!"), "stack!");
+      } catch (e) {
+      }
+      expect(log.result()).toContain("stack!");
+    });
+
+    it("should join a long stackTrace", () => {
+      try {
+        handler.call(new BaseException("message!"), ["stack1", "stack2"]);
+      } catch (e) {
+      }
+      expect(log.result()).toContain("stack1");
+      expect(log.result()).toContain("stack2");
+    });
+
+    it("should output reason when present", () => {
+      try {
+        handler.call(new BaseException("message!"), null, "reason!");
+      } catch (e) {
+      }
+      expect(log.result()).toContain("reason!");
+    });
+
+    it("should print context", () => {
+      try {
+        handler.call(new BaseException("message!", null, null, "context!"));
+      } catch (e) {
+      }
+      expect(log.result()).toContain("context!");
+    });
+
+    it("should print nested context", () => {
+      try {
+        var original = new BaseException("message!", null, null, "context!");
+        handler.call(new BaseException("message", original));
+      } catch (e) {
+      }
+      expect(log.result()).toContain("context!");
+    });
+
+    it("should not print context when the passed-in exception is not a BaseException", () => {
+      try {
+        handler.call(new _CustomException());
+      } catch (e) {
+      }
+      expect(log.result()).not.toContain("context");
+    });
+  });
+}