How do I pass plain text as my request body using NestJS?

I see that this question is pretty old, but it is listed in google among first, so I want to add answer here.

If you don't want to add body-parser middleware (for example, you want plain text only in single controller method), you can use raw-body (which is already exists in your node_modules), something like this:

import * as rawbody from 'raw-body';
import { Controller, Post, Body, Req } from '@nestjs/common';

@Controller('/')
export class IndexController {

  @Post()
  async index(@Body() data, @Req() req) {

    // we have to check req.readable because of raw-body issue #57
    // https://github.com/stream-utils/raw-body/issues/57
    if (req.readable) {
      // body is ignored by NestJS -> get raw body from request
      const raw = await rawbody(req);
      const text = raw.toString().trim();
      console.log('body:', text);

    } else {
      // body is parsed by NestJS
      console.log('data:', data);
    }

    // ...
  }

}

you could also create new parameter decorator

import * as rawbody from 'raw-body';
import { createParamDecorator, HttpException, HttpStatus } from '@nestjs/common';

export const PlainBody = createParamDecorator(async (data, req) => {
  if (req.readable) {
    return (await rawbody(req)).toString().trim();
  }
  throw new HttpException('Body aint text/plain', HttpStatus.INTERNAL_SERVER_ERROR);
});

and use it like

@Post()
async index(@PlainBody() text: string) {
  // ...

(I didn't check decorator code, wrote it right here in comment)

Adding on @yumaa's post above

Here's the working decorator with NestJS v7.0.8:

import { createParamDecorator, ExecutionContext, BadRequestException } from '@nestjs/common';
import * as rawBody from "raw-body";

export const PlainBody = createParamDecorator(async (_, context: ExecutionContext) => {
    const req = context.switchToHttp().getRequest<import("express").Request>();
    if (!req.readable) { throw new BadRequestException("Invalid body"); }

    const body = (await rawBody(req)).toString("utf8").trim();
    return body;
})