Merge pull request #171 from NativeScript/nnikolov/CssParserErrorMessage

Binding converter run-time errors logging on console.

apps/tests/app/binding_tests.ts

@@ -32,13 +32,38 @@ export function pageLoaded(args: observableModule.EventData) {
     model.set("toUpper", toUpperConverter);
     model.set("testProperty", "Alabala");
 
+    var dateConverter = {
+        toView: function (value, format) {
+            var result = format;
+            var day = value.getDate();
+            result = result.replace("dd", month < 10 ? "0" + day : day);
+            var month = value.getMonth() + 1;
+            result = result.replace("mm", month < 10 ? "0" + month : month);
+            result = result.replace("yyyy", value.getFullYear());
+            return result;
+        },
+        toModel: function (value, format) {
+            var ddIndex = format.indexOf("dd");
+            var day = parseInt(value.substr(ddIndex, 2));
+            var mmIndex = format.indexOf("mm");
+            var month = parseInt(value.substr(mmIndex, 2));
+            var yyyyIndex = format.indexOf("yyyy");
+            var year = parseInt(value.substr(yyyyIndex, 4));
+            var result = new Date(year, month - 1, day);
+            return result;
+        }
+    }
+
+    model.set("dateConverter", dateConverter);
+    model.set("testDate", new Date());
+
     page.bindingContext = model;
 }
 
 export function onTap(args: observableModule.EventData) {
     var button: buttonModule.Button = <buttonModule.Button>args.object;
-    trace.write("tasks: " + button.bindingContext.get("tasks"), trace.categories.Test, trace.messageType.info);
+    trace.write("tasks: " + button.bindingContext.get("testDate"), trace.categories.Test, trace.messageType.info);
-    button.bindingContext.get("tasks").push("alabala");
+    //button.bindingContext.get("tasks").push("alabala");
 }
 
 //export function createPage() {

apps/tests/app/binding_tests.xml

@@ -1,6 +1,8 @@
 <Page xmlns="http://www.nativescript.org/tns.xsd" loaded="pageLoaded">
     <StackLayout padding="7">
-        <TextField text="{{ tasks.length, tasks.length === 0 ? 'zero items' : tasks.length + ' items', false }}" />
+        <!--<TextField text="{{ tasks.length, tasks.length === 0 ? 'zero items' : tasks.length + ' items', false }}" />-->
+        <TextField text="{{ testDate, testDate | dateConverter('dd.mm.yyyy') }}" updateTextTrigger="textChanged"/>
+        <TextField text="{{ testDate }}" />
         <Button text="Click" tap="onTap" />
     </StackLayout>
 </Page>

ui/core/bindable.ts

@@ -225,7 +225,13 @@ export class Binding {
             if (this._isExpression(this.options.expression)) {
                 var changedModel = {};
                 changedModel[this.options.sourceProperty] = value;
-                this.updateSource(this._getExpressionValue(this.options.expression, true, changedModel));
+                var expressionValue = this._getExpressionValue(this.options.expression, true, changedModel);
+                if (expressionValue instanceof Error) {
+                    trace.write((<Error>expressionValue).message, trace.categories.Binding, trace.messageType.error);
+                }
+                else {
+                    this.updateSource(expressionValue);
+                }
             }
             else {
                 this.updateSource(value);
@@ -250,16 +256,23 @@ export class Binding {
                 var context = this.source && this.source.get && this.source.get() || global;
                 return exp.getValue(context, isBackConvert, changedModel);
             }
-            return undefined;
+            return new Error(expression + " is not a valid expression.");
         }
         catch (e) {
-            return undefined;
+            var errorMessage = "Run-time error occured in file: " + e.sourceURL + " at line: " + e.line + " and column: " + e.column; 
+            return new Error(errorMessage);
         }
     }
 
     public onSourcePropertyChanged(data: observable.PropertyChangeData) {
         if (this._isExpression(this.options.expression)) {
-            this.updateTarget(this._getExpressionValue(this.options.expression, false, undefined));
+            var expressionValue = this._getExpressionValue(this.options.expression, false, undefined);
+            if (expressionValue instanceof Error) {
+                trace.write((<Error>expressionValue).message, trace.categories.Binding, trace.messageType.error);
+            }
+            else {
+                this.updateTarget(expressionValue);
+            }
         } else if (data.propertyName === this.options.sourceProperty) {
             this.updateTarget(data.value);
         }
@@ -267,7 +280,13 @@ export class Binding {
 
     private getSourceProperty() {
         if (this._isExpression(this.options.expression)) {
-            return this._getExpressionValue(this.options.expression, false, undefined);
+            var expressionValue = this._getExpressionValue(this.options.expression, false, undefined);
+            if (expressionValue instanceof Error) {
+                trace.write((<Error>expressionValue).message, trace.categories.Binding, trace.messageType.error);
+            }
+            else {
+                return expressionValue;
+            }
         }
 
         if (!this.sourceOptions) {