I think it's done?

src/ObjectCollections/MongoStoredObjectCollection.ts

@@ -1,6 +1,6 @@
 import mongo from "mongodb";
-import {tryQuery} from "./database";
-import {MongoError} from "../errors";
+import {tryQuery} from "../database";
+import {InvalidIdError, MongoError} from "../errors";
 import ActiveRecord, {ActiveRecordId} from "../Objects/ActiveRecord";
 
 
@@ -19,10 +19,15 @@ abstract class MongoStoredObjectCollection<IRawData extends {id: ActiveRecordId}
         });
     }
 
-    protected async mongoRead(id: string): Promise<IRawData | null> {
-        return tryQuery(async () =>
-            await this.mongoDbClientCollection.findOne({_id: id})
-        );
+    protected async mongoRead(id: string): Promise<IRawData> {
+        return tryQuery(async () => {
+            const result = await this.mongoDbClientCollection.findOne({_id: id});
+            if (result) {
+                return result;
+            } else {
+                throw new InvalidIdError(`Object in collection "${typeof this}" with id ${JSON.stringify(id)} not found!`);
+            }
+        });
     }
 
     protected async mongoFindByAttribute(attribute: string, value: any): Promise<IRawData | null> {
@@ -31,7 +36,7 @@ abstract class MongoStoredObjectCollection<IRawData extends {id: ActiveRecordId}
         );
     }
 
-    protected async mongoDelete(objectId: ActiveRecordId, returnObject?: boolean): Promise<IRawData | null | void> {
+    protected async mongoDelete(objectId: ActiveRecordId, returnObject?: boolean): Promise<IRawData | void> {
         let deletedObject;
         if (returnObject ?? true) {
             deletedObject = await this.mongoRead(objectId);
@@ -40,15 +45,19 @@ abstract class MongoStoredObjectCollection<IRawData extends {id: ActiveRecordId}
         if (deleteWriteOpResult.result.ok === 1) {
             return deletedObject;
         } else {
-            throw new MongoError(`Error deleting the object with id: ${JSON.stringify(objectId)}`);
+            throw new MongoError(`Error deleting the object in collection "${typeof this}" with id: ${JSON.stringify(objectId)}`);
         }
     }
 
-    protected async mongoSave(object: IRawData) {
+    protected async mongoUpdate(object: Partial<IRawData> & {id: ActiveRecordId}) {
         await tryQuery(() =>
             this.mongoDbClientCollection.findOneAndUpdate({_id: object.id}, {$set: {...object, id: undefined}})
         );
     }
+
+    protected idFromRecordOrId<T extends ActiveRecord>(recordOrRecordId: T | ActiveRecordId): ActiveRecordId {
+        return typeof recordOrRecordId === "string" ? recordOrRecordId : recordOrRecordId.getId();
+    }
 }