feat(core): add dynamic error messages

src/throttler-module-options.interface.ts

@@ -1,5 +1,6 @@
 import { ExecutionContext, ModuleMetadata, Type } from '@nestjs/common/interfaces';
 import { ThrottlerStorage } from './throttler-storage.interface';
+import { ThrottlerLimitDetail } from './throttler.guard.interface';
 
 export type Resolvable<T extends number | string | boolean> =
   | T
@@ -72,7 +73,9 @@ export type ThrottlerModuleOptions =
       /**
        * An optional message to override the default error message.
        */
-      errorMessage?: string;
+      errorMessage?:
+        | string
+        | ((context: ExecutionContext, throttlerLimitDetail: ThrottlerLimitDetail) => string);
 
       /**
        * The storage class to use where all the record will be stored in.

src/throttler.guard.ts

@@ -224,7 +224,11 @@ export class ThrottlerGuard implements CanActivate {
     _throttlerLimitDetail: ThrottlerLimitDetail,
   ): Promise<string> {
     if (!Array.isArray(this.options)) {
-      return this.options.errorMessage || this.errorMessage;
+      if (!this.options.errorMessage) return this.errorMessage;
+
+      return typeof this.options.errorMessage === 'function'
+        ? this.options.errorMessage(_context, _throttlerLimitDetail)
+        : this.options.errorMessage;
     }
     return this.errorMessage;
   }

test/error-message/app.module.ts

@@ -0,0 +1,35 @@
+import { Module } from '@nestjs/common';
+import { APP_GUARD } from '@nestjs/core';
+import { seconds, ThrottlerGuard, ThrottlerModule } from '../../src';
+import { CustomErrorMessageController } from './custom-error-message.controller';
+
+@Module({
+  imports: [
+    ThrottlerModule.forRoot({
+      errorMessage: (context, throttlerLimitDetail) =>
+        `${context.getClass().name}-${
+          context.getHandler().name
+        } ${throttlerLimitDetail.tracker} ${throttlerLimitDetail.totalHits}`,
+      throttlers: [
+        {
+          name: 'default',
+          ttl: seconds(3),
+          limit: 2,
+        },
+        {
+          name: 'other',
+          ttl: seconds(3),
+          limit: 2,
+        },
+      ],
+    }),
+  ],
+  controllers: [CustomErrorMessageController],
+  providers: [
+    {
+      provide: APP_GUARD,
+      useClass: ThrottlerGuard,
+    },
+  ],
+})
+export class CustomErrorMessageThrottlerModule {}

test/error-message/custom-error-message.controller.ts

@@ -0,0 +1,17 @@
+import { Controller, Get } from '@nestjs/common';
+import { SkipThrottle } from '../../src';
+
+@Controller()
+export class CustomErrorMessageController {
+  @SkipThrottle({ other: true })
+  @Get('default')
+  defaultRoute() {
+    return { success: true };
+  }
+
+  @SkipThrottle({ default: true })
+  @Get('other')
+  otherRoute() {
+    return { success: true };
+  }
+}

test/error-message/custom-error-message.e2e-spec.ts

@@ -0,0 +1,49 @@
+import { INestApplication, Type } from '@nestjs/common';
+import { AbstractHttpAdapter } from '@nestjs/core';
+import { ExpressAdapter } from '@nestjs/platform-express';
+import { FastifyAdapter } from '@nestjs/platform-fastify';
+import { Test } from '@nestjs/testing';
+import { request, spec } from 'pactum';
+import { CustomErrorMessageThrottlerModule } from './app.module';
+
+jest.setTimeout(10000);
+
+describe.each`
+  adapter           | name
+  ${ExpressAdapter} | ${'express'}
+  ${FastifyAdapter} | ${'fastify'}
+`(
+  'Function-Overrides-Throttler Named Usage - $name',
+  ({ adapter }: { adapter: Type<AbstractHttpAdapter> }) => {
+    let app: INestApplication;
+    beforeAll(async () => {
+      const modRef = await Test.createTestingModule({
+        imports: [CustomErrorMessageThrottlerModule],
+      }).compile();
+      app = modRef.createNestApplication(new adapter());
+      await app.listen(0);
+      request.setBaseUrl(await app.getUrl());
+    });
+    afterAll(async () => {
+      await app.close();
+    });
+
+    describe.each`
+      route        | errorMessage
+      ${'default'} | ${'CustomErrorMessageController-defaultRoute ::1 3'}
+      ${'other'}   | ${'CustomErrorMessageController-otherRoute ::1 3'}
+    `(
+      'Custom-error-message Route - $route',
+      ({ route, errorMessage }: { route: string; errorMessage: string }) => {
+        it('should receive a custom exception', async () => {
+          const limit = 2;
+          for (let i = 0; i < limit; i++) {
+            await spec().get(`/${route}`).expectStatus(200);
+          }
+
+          await spec().get(`/${route}`).expectStatus(429).expectBodyContains(errorMessage);
+        });
+      },
+    );
+  },
+);