defect(expressionJs): return undefined if variable not exist in model (…

…#8)

* Check if expression is invalid
* check if dependencies is not exist in model and return undefined

Covers [UID-630](https://bonitasoft.atlassian.net/browse/UID-630)

src/resolvers/ExpressionResolver.ts

@@ -11,16 +11,20 @@ export class ExpressionResolver extends Resolver {
 
     resolve(): void {
         // use strict. Avoid pollution of the global object.
-        let expression = new Function(
-            '$data',//inject all data
-            'uiTranslate',//inject translate function
-            '"use strict";' + this.content);
+        try {
+            let expression = new Function(
+                '$data',//inject all data
+                'uiTranslate',//inject translate function
+                '"use strict";' + this.content);
 
-        this.model[this.name] = expression(
-            this.model, // all data
-            //TODO Implement Translate
-            (text: string) => text// translate function
-        );
+            this.model[this.name] = expression(
+                this.model, // all data
+                //TODO Implement Translate
+                (text: string) => text// translate function
+            );
+        }catch (e) {
+            console.error('This following error occur on expression resolution',e);
+        }
     }
 
     hasDependencies(): boolean {

tests/resolvers/ExpressionResolver.spec.ts

@@ -28,4 +28,22 @@ describe('expressionResolver', () => {
         expect(typeof model.myJsVar).to.equal("string");
         expect(model.myJsVar).to.equal('return "Hello here"');
     });
+
+    it('should return undefined when referenced variable is not exist in model', () => {
+        let expression = new ExpressionResolver(model, 'myJsVar', 'return $data.unknownVariable');
+
+        expression.resolve();
+
+        expect(expression.hasDependencies()).to.equal(true);
+        expect(model.myJsVar).to.equal(undefined);
+    });
+
+    it('should return undefined when variable used in expression is invalid', () => {
+        let expression = new ExpressionResolver(model, 'myJsVar', 'return $unknownVariable');
+
+        expression.resolve();
+
+        expect(expression.hasDependencies()).to.equal(false);
+        expect(model.myJsVar).to.equal(undefined);
+    });
 });