Add error messages to Pipes

lib/utils/pipes.js

@@ -1,6 +1,7 @@
 'use strict';
 
-import {Pipe} from 'angular2/core';
+import {Pipe, InvalidPipeArgumentException} from 'angular2/core';
+import {isString} from 'angular2/src/facade/lang';
 import {JsonPointer} from './JsonPointer';
 import marked from 'marked';
 
@@ -15,39 +16,42 @@ marked.setOptions({
 });
 
 
-@Pipe({
-  name: 'keys'
-})
+@Pipe({ name: 'keys' })
 export class KeysPipe {
   transform(obj) {
+    if (typeof obj !== 'object') {
+      throw new InvalidPipeArgumentException(ValuesPipe, obj);
+    }
     return Object.keys(obj);
   }
 }
 
-@Pipe({
-  name: 'values'
-})
+@Pipe({ name: 'values' })
 export class ValuesPipe {
-  transform(obj) {
-    return Object.keys(obj).map(key => obj[key]);
+  transform(value) {
+    if (typeof value !== 'object') {
+      throw new InvalidPipeArgumentException(ValuesPipe, value);
+    }
+    return Object.keys(value).map(key => value[key]);
   }
 }
 
-@Pipe({
-  name: 'jsonPointerEscape'
-})
+@Pipe({ name: 'jsonPointerEscape' })
 export class JsonPointerEscapePipe {
-  transform(str) {
-    return JsonPointer.escape(str);
+  transform(value) {
+    if (!isString(value)) {
+      throw new InvalidPipeArgumentException(JsonPointerEscapePipe, value);
+    }
+    return JsonPointer.escape(value);
   }
 }
 
-@Pipe({
-  name: 'marked'
-})
+@Pipe({ name: 'marked' })
 export class MarkedPipe {
-  transform(str) {
-    if (!str) return str;
-    return marked(str);
+  transform(value) {
+    if (!isString(value)) {
+      throw new InvalidPipeArgumentException(JsonPointerEscapePipe, value);
+    }
+    return marked(value);
   }
 }