fix: workaround for @IsEnum({ ..., isArray: true }) when used in @Query

Author: glebbash

src/decorators/is-enum.spec.ts

@@ -1,6 +1,7 @@
+import { Controller, Get, Query } from '@nestjs/common';
 import { Result } from 'true-myth';
 
-import { generateSchemas, input, make } from '../../tests/helpers';
+import { generateSchemas, generateSpec, input, make } from '../../tests/helpers';
 import { IsEnum } from '../nestjs-swagger-dto';
 
 describe('IsEnum', () => {
@@ -153,6 +154,48 @@ describe('IsEnum', () => {
       });
     });
 
+    it('generates correct schema including minLength and maxLength when used in @Query', async () => {
+      enum Flag {
+        On = 'On',
+        Off = 'Off',
+      }
+
+      class TestQuery {
+        @IsEnum({
+          enum: { Flag },
+          isArray: { minLength: 1, maxLength: 2, force: true },
+          optional: true,
+        })
+        enumField?: Flag;
+      }
+
+      @Controller('x')
+      class AppController {
+        @Get()
+        someEndpoint(@Query() {}: TestQuery) {}
+      }
+
+      const spec = await generateSpec([AppController]);
+
+      expect(spec.paths['/x'].get).toStrictEqual({
+        operationId: 'AppController_someEndpoint',
+        parameters: [
+          {
+            in: 'query',
+            name: 'enumField',
+            required: false,
+            schema: {
+              items: { $ref: '#/components/schemas/Flag' },
+              maxItems: 2,
+              minItems: 1,
+              type: 'array',
+            },
+          },
+        ],
+        responses: { '200': { description: '' } },
+      });
+    });
+
     it('accepts enum arrays', async () => {
       expect(await input(Test, { enumField: ['a', 'b'] })).toStrictEqual(
         Result.ok(make(Test, { enumField: ['a', 'b'] })),

src/decorators/is-enum.ts

@@ -1,3 +1,4 @@
+import { ApiPropertyOptions, getSchemaPath } from '@nestjs/swagger';
 import { IsIn } from 'class-validator';
 
 import { compose, PropertyOptions } from '../core';
@@ -20,18 +21,24 @@ export const IsEnum = <T extends number | string>({
 }: PropertyOptions<T, { enum: EnumOptions<T> }>): PropertyDecorator => {
   const { enumValues, enumName } = getEnumNameAndValues(enumOptions);
 
-  return compose(
-    { type: typeof enumValues[0], enum: enumValues, enumName },
-    base,
-    IsIn(enumValues, { each: !!base.isArray }),
-  );
+  let apiPropertyOptions: ApiPropertyOptions = {
+    type: typeof enumValues[0],
+    enum: enumValues,
+    enumName,
+  };
+  // workaround for Nest's @Query handling
+  if (typeof base.isArray === 'object' && base.isArray.force) {
+    apiPropertyOptions = { type: 'array', items: { $ref: getSchemaPath(enumName) } };
+  }
+
+  return compose(apiPropertyOptions, base, IsIn(enumValues, { each: !!base.isArray }));
 };
 
 function getEnumNameAndValues<T extends number | string>(
   e: EnumOptions<T>,
 ): {
   enumValues: T[];
-  enumName?: string;
+  enumName: string;
 } {
   const keys = Object.keys(e);
   if (keys.length !== 1) {

tests/helpers.ts

@@ -1,4 +1,4 @@
-import { INestApplication, Type } from '@nestjs/common';
+import { INestApplication, Module, Type } from '@nestjs/common';
 import { NestFactory } from '@nestjs/core';
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
 import type {
@@ -47,14 +47,19 @@ function getValidationError(error: ValidationError): string {
 export async function generateSchemas(
   models: Type[],
 ): Promise<Record<string, SchemaObject | ReferenceObject>> {
+  const spec = await generateSpec([], models);
+
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  return spec.components!.schemas!;
+}
+
+export async function generateSpec(controllers: Type[], extraModels: Type[] = []) {
+  @Module({ controllers })
   class AppModule {}
 
-  const spec = SwaggerModule.createDocument(
+  return SwaggerModule.createDocument(
     await NestFactory.create<INestApplication>(AppModule, { logger: false }),
     new DocumentBuilder().build(),
-    { extraModels: models },
+    { extraModels },
   );
-
-  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-  return spec.components!.schemas!;
 }