fix(replaceFieldOperator): disallow to pass null because it will emulate instead to remove the operator

packages/datasource-customizer/src/decorators/operators-emulate/collection.ts

@@ -21,13 +21,22 @@ import CollectionCustomizationContext from '../../context/collection-context';
 
 export default class OperatorsEmulateCollectionDecorator extends CollectionDecorator {
   override readonly dataSource: DataSourceDecorator<OperatorsEmulateCollectionDecorator>;
-  private readonly fields: Map<string, Map<Operator, OperatorDefinition>> = new Map();
+  private readonly fields: Map<string, Map<Operator, OperatorDefinition | null>> = new Map();
 
   emulateFieldOperator(name: string, operator: Operator): void {
-    this.replaceFieldOperator(name, operator, null);
+    this.replaceOrEmulateFieldOperator(name, operator, null);
   }
 
   replaceFieldOperator(name: string, operator: Operator, replaceBy: OperatorDefinition): void {
+    if (!replaceBy) throw new Error('replaceBy handler is required');
+    this.replaceOrEmulateFieldOperator(name, operator, replaceBy);
+  }
+
+  private replaceOrEmulateFieldOperator(
+    name: string,
+    operator: Operator,
+    replaceBy: OperatorDefinition | null,
+  ): void {
     // Check that the collection can actually support our rewriting
     const pks = SchemaUtils.getPrimaryKeys(this.childCollection.schema);
     pks.forEach(pk => {

packages/datasource-customizer/test/decorators/operators-emulate/collection.test.ts

@@ -157,6 +157,12 @@ describe('OperatorsEmulateCollectionDecorator', () => {
       });
     });
 
+    test('replaceFieldOperator() should throw if no handler is given', () => {
+      expect(() => newBooks.replaceFieldOperator('title', 'StartsWith', null)).toThrow(
+        'replaceBy handler is required',
+      );
+    });
+
     describe('when creating a cycle in the replacements graph', () => {
       beforeEach(() => {
         newBooks.replaceFieldOperator('title', 'StartsWith', async value => ({