fix: we now allow empty lambda operations (#822)

The code was always expecting an expression.
Fixes internal issue 247

.changeset/ten-bags-sin.md

@@ -0,0 +1,5 @@
+---
+'@sap-ux/fe-mockserver-core': patch
+---
+
+fix: allow empty lambda operations

packages/fe-mockserver-core/src/data/entitySets/entitySet.ts

@@ -413,7 +413,7 @@ export class MockDataEntitySet implements EntitySetInterface {
         if (!Array.isArray(mockDataToCheckValue)) {
             mockDataToCheckValue = [mockDataToCheckValue];
         }
-        if (expression.expression.expressions) {
+        if (expression.expression?.expressions) {
             expression.expression.expressions.forEach((entry: any) => {
                 const replaceValue = expression.propertyPath || expression.target;
                 if (typeof entry.identifier === 'string') {
@@ -426,6 +426,9 @@ export class MockDataEntitySet implements EntitySetInterface {
                     );
                 }
             });
+        } else {
+            // no expressions, so empty lambda
+            return true;
         }
 
         const check = (subMockData: any) => {

packages/fe-mockserver-core/test/unit/data/entitySet.test.ts

@@ -55,6 +55,9 @@ describe('EntitySet', () => {
             expect(filteredData).toBe(false);
             filteredData = myEntitySet.checkFilter(mockData[3], v4ComplexLambda, 'default', fakeRequest);
             expect(filteredData).toBe(false);
+            const v4SimpleLambda = parseFilter('ArrayData/any()')!;
+            filteredData = myEntitySet.checkFilter(mockData[0], v4SimpleLambda, 'default', fakeRequest);
+            expect(filteredData).toBe(true);
         });
         it('works on deep lambda expression with methods', async () => {
             const myEntitySet = new MockDataEntitySet(