fix(graphql): pagination offset should never be below zero

src/app/modules/angular-slickgrid/services/__tests__/graphql.service.spec.ts

@@ -221,6 +221,28 @@ describe('GraphqlService', () => {
       expect(removeSpaces(query)).toBe(removeSpaces(expectation));
     });
 
+    it('should make sure the offset pagination is never below zero, even when new page is 0', () => {
+      const expectation = `query{ users(first:20, offset:0){ totalCount, nodes{ id, field1, field2 }}}`;
+      const columns = [{ id: 'field1', field: 'field1', width: 100 }, { id: 'field2', field: 'field2', width: 100 }];
+
+      service.init({ datasetName: 'users', columnDefinitions: columns }, paginationOptions, gridStub);
+      service.updatePagination(0, 20);
+      const query = service.buildQuery();
+
+      expect(removeSpaces(query)).toBe(removeSpaces(expectation));
+    });
+
+    it('should make sure the offset pagination is never below zero, even when new is 1 the offset should remain 0', () => {
+      const expectation = `query{ users(first:20, offset:0){ totalCount, nodes{ id, field1, field2 }}}`;
+      const columns = [{ id: 'field1', field: 'field1', width: 100 }, { id: 'field2', field: 'field2', width: 100 }];
+
+      service.init({ datasetName: 'users', columnDefinitions: columns }, paginationOptions, gridStub);
+      service.updatePagination(1, 20);
+      const query = service.buildQuery();
+
+      expect(removeSpaces(query)).toBe(removeSpaces(expectation));
+    });
+
     it('should be able to provide "sortingOptions" and see the query string include the sorting', () => {
       const expectation = `query{ users(first:20, offset:40,orderBy:[{field:field1, direction:DESC}]){ totalCount, nodes{ id, field1, field2 }}}`;
       const columns = [{ id: 'field1', field: 'field1', width: 100 }, { id: 'field2', field: 'field2', width: 100 }];

src/app/modules/angular-slickgrid/services/graphql.service.ts

@@ -462,7 +462,7 @@ export class GraphqlService implements BackendService {
     } else {
       paginationOptions = {
         first: pageSize,
-        offset: (newPage - 1) * pageSize
+        offset: (newPage > 1) ? ((newPage - 1) * pageSize) : 0 // recalculate offset but make sure the result is always over 0
       };
     }