fix: error message delete assignment knop met vragen of submissions

backend/src/services/assignments.ts

@@ -14,11 +14,14 @@ import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submissi
 import { fetchClass } from './classes.js';
 import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
-import { EntityDTO } from '@mikro-orm/core';
+import {EntityDTO, ForeignKeyConstraintViolationException} from '@mikro-orm/core';
 import { putObject } from './service-helper.js';
 import { fetchStudents } from './students.js';
 import { ServerErrorException } from '../exceptions/server-error-exception.js';
 import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import {getQuestionsAboutLearningObjectInAssignment} from "./questions";
+import {LearningObjectIdentifier} from "../entities/content/learning-object-identifier";
+import {ConflictException} from "../exceptions/conflict-exception";
 
 export async function fetchAssignment(classid: string, assignmentNumber: number): Promise<Assignment> {
     const classRepository = getClassRepository();
@@ -133,7 +136,13 @@ export async function deleteAssignment(classid: string, id: number): Promise<Ass
     const cls = await fetchClass(classid);
 
     const assignmentRepository = getAssignmentRepository();
+
+    try {
         await assignmentRepository.deleteByClassAndId(cls, id);
+    } catch (e: ForeignKeyConstraintViolationException) {
+        throw new ConflictException("Cannot delete assigment with questions or submissions")
+    }
+
 
     return mapToAssignmentDTO(assignment);
 }

frontend/src/views/assignments/TeacherAssignment.vue

@@ -87,6 +87,18 @@
         dialog.value = true;
     }
 
+    const snackbar = ref({
+        visible: false,
+        message: "",
+        color: "success",
+    });
+
+    function showSnackbar(message: string, color: string): void {
+        snackbar.value.message = message;
+        snackbar.value.color = color;
+        snackbar.value.visible = true;
+    }
+
     const deleteAssignmentMutation = useDeleteAssignmentMutation();
     async function deleteAssignment(num: number, clsId: string): Promise<void> {
         deleteAssignmentMutation.mutate(
@@ -95,6 +107,9 @@
                 onSuccess: () => {
                     window.location.href = "/user/assignment";
                 },
+                onError: (e) => {
+                    showSnackbar(t("failed") + ": " + e.response.data.error || e.message, "error");
+                }
             },
         );
     }
@@ -458,6 +473,13 @@
                     </v-card>
                 </v-dialog>
             </v-container>
+            <v-snackbar
+                v-model="snackbar.visible"
+                :color="snackbar.color"
+                timeout="3000"
+            >
+                {{ snackbar.message }}
+            </v-snackbar>
         </using-query-result>
     </div>
 </template>