fix(schema-generator): throw error when type is ambiguous

Author: kamilmysliwiec

lib/decorators/prop.decorator.ts

@@ -1,4 +1,5 @@
 import * as mongoose from 'mongoose';
+import { CannotDetermineTypeError } from '../errors';
 import { RAW_OBJECT_DEFINITION } from '../mongoose.constants';
 import { TypeMetadataStorage } from '../storages/type-metadata.storage';
 
@@ -29,7 +30,10 @@ export function Prop(options?: PropOptions): PropertyDecorator {
       } else if (type && type !== Object) {
         options.type = type;
       } else {
-        options.type = mongoose.SchemaTypes.Mixed;
+        throw new CannotDetermineTypeError(
+          target.constructor?.name,
+          propertyKey as string,
+        );
       }
     }
 

lib/errors/cannot-determine-type.error.ts

@@ -0,0 +1,7 @@
+export class CannotDetermineTypeError extends Error {
+  constructor(hostClass: string, propertyKey: string) {
+    super(
+      `Cannot determine a type for the "${hostClass}.${propertyKey}" field (union/intersection/ambiguous type was used). Make sure your property is decorated with a "@Prop({ type: TYPE_HERE })" decorator.`,
+    );
+  }
+}

lib/errors/index.ts

@@ -0,0 +1 @@
+export * from './cannot-determine-type.error';

lib/index.ts

@@ -1,5 +1,6 @@
 export * from './common';
 export * from './decorators';
+export * from './errors';
 export * from './factories';
 export * from './interfaces';
 export * from './mongoose.module';

tests/e2e/schema-definitions.factory.spec.ts

@@ -1,5 +1,6 @@
 import * as mongoose from 'mongoose';
 import { DefinitionsFactory, Prop, raw, Schema } from '../../lib';
+import { CannotDetermineTypeError } from '../../lib/errors';
 
 @Schema()
 class ChildClass {
@@ -18,9 +19,6 @@ class ExampleClass {
   @Prop({ required: true })
   name: string;
 
-  @Prop({ required: true })
-  object: object;
-
   @Prop()
   buffer: mongoose.Schema.Types.Buffer;
 
@@ -59,7 +57,7 @@ class ExampleClass {
   @Prop(raw({ custom: 'literal', object: true }))
   customObject: any;
 
-  @Prop()
+  @Prop({ type: mongoose.Schema.Types.Mixed })
   any: any;
 
   @Prop()
@@ -77,10 +75,6 @@ describe('DefinitionsFactory', () => {
         required: true,
         type: String,
       },
-      object: {
-        required: true,
-        type: mongoose.SchemaTypes.Mixed,
-      },
       nodes: [
         {
           id: {
@@ -104,7 +98,7 @@ describe('DefinitionsFactory', () => {
           },
         },
       },
-      any: { type: mongoose.SchemaTypes.Mixed },
+      any: { type: mongoose.Schema.Types.Mixed },
       array: { type: [] },
       customArray: [{ custom: 'literal', object: true }],
       customObject: { custom: 'literal', object: true },
@@ -122,4 +116,19 @@ describe('DefinitionsFactory', () => {
       number: { type: Number },
     });
   });
+
+  it('should throw an error when type is ambiguous', () => {
+    try {
+      class AmbiguousField {
+        @Prop()
+        randomField: object | null;
+      }
+      DefinitionsFactory.createForClass(AmbiguousField);
+    } catch (err) {
+      expect(err).toBeInstanceOf(CannotDetermineTypeError);
+      expect(err.message).toEqual(
+        'Cannot determine a type for the "AmbiguousField.randomField" field (union/intersection/ambiguous type was used). Make sure your property is decorated with a "@Prop({ type: TYPE_HERE })" decorator.',
+      );
+    }
+  });
 });

tests/src/event/event.service.ts

@@ -1,5 +1,5 @@
 import { Injectable } from '@nestjs/common';
-import { Model, Document } from 'mongoose';
+import { Document, Model } from 'mongoose';
 import { InjectModel } from '../../../lib';
 import { CreateClickLinkEventDto } from './dto/create-click-link-event.dto';
 import { CreateSignUpEventDto } from './dto/create-sign-up-event.dto';
@@ -13,10 +13,10 @@ export class EventService {
   ) {}
 
   async create(
-    createCatDto: CreateClickLinkEventDto | CreateSignUpEventDto,
+    createDto: CreateClickLinkEventDto | CreateSignUpEventDto,
   ): Promise<Event> {
-    const createdCat = new this.eventModel(createCatDto);
-    return createdCat.save();
+    const createdEvent = new this.eventModel(createDto);
+    return createdEvent.save();
   }
 
   async findAll(): Promise<Event[]> {