Merge pull request #2655 from tolgap/use-body-parser

docs(raw-body): add examples and explainers for body parser limits with `app.useBodyParser`

Author: kamilmysliwiec

content/faq/raw-body.md

@@ -42,16 +42,31 @@ By default, only `json` and `urlencoded` parsers are registered. If you want to
 For example, to register a `text` parser, you can use the following code:
 
 ```typescript
-app.useBodyParser('text')
+app.useBodyParser('text');
 ```
 
+> warning **Warning** Ensure that you are providing the correct application type to the `NestFactory.create` call. For Express applications, the correct type is `NestExpressApplication`. Otherwise the `.useBodyParser` method will not be found.
+
+#### Body parser size limit
+
+If your application needs to parse a body larger than the default `100kb` of Express, use the following:
+
+```typescript
+app.useBodyParser('json', { limit: '10mb' });
+```
+
+The `.useBodyParser` method will respect the `rawBody` option that is passed in the application options.
+
 #### Use with Fastify
 
 First enable the option when creating your Nest Fastify application:
 
 ```typescript
 import { NestFactory } from '@nestjs/core';
-import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify';
+import {
+  FastifyAdapter,
+  NestFastifyApplication,
+} from '@nestjs/platform-fastify';
 import { AppModule } from './app.module';
 
 // in the "bootstrap" function
@@ -60,7 +75,7 @@ const app = await NestFactory.create<NestFastifyApplication>(
   new FastifyAdapter(),
   {
     rawBody: true,
-  }
+  },
 );
 await app.listen(3000);
 ```
@@ -87,5 +102,18 @@ By default, only `application/json` and `application/x-www-form-urlencoded` pars
 For example, to register a `text/plain` parser, you can use the following code:
 
 ```typescript
-app.useBodyParser('text/plain')
+app.useBodyParser('text/plain');
 ```
+
+> warning **Warning** Ensure that you are providing the correct application type to the `NestFactory.create` call. For Fastify applications, the correct type is `NestFastifyApplication`. Otherwise the `.useBodyParser` method will not be found.
+
+#### Body parser size limit
+
+If your application needs to parse a body larger than the default 1MiB of Fastify, use the following:
+
+```typescript
+const bodyLimit = 10_485_760; // 10MiB
+app.useBodyParser('application/json', { bodyLimit });
+```
+
+The `.useBodyParser` method will respect the `rawBody` option that is passed in the application options.