ValidationPipe sets "undefined" for Boolean parameter if not provided

[myfunc]

Did you read the migration guide?

• I have read the whole migration guide

Is there an existing issue that is already proposing this?

• I have searched the existing issues

Potential Commit/PR that introduced the regression

PR #10953

NestJS version

9.4.3 -> 10.2.10

Describe the regression

I encountered a breaking change while migrating to the new major version of Nest.js.

In version 9.4.3, the ParseBoolPipe from "@nestjs/common" used to set a parameter's value to "false" if it was not provided. Starting from version 10.0.0, the ValidationPipe::transformPrimitive() now sets a Boolean parameter to "undefined."

Unfortunately, this change is not mentioned in the Nest.js migration guide https://docs.nestjs.com/migration-guide and is not highlighted in the release notes.

Minimum reproduction code

No response

Input code

import {
  Controller,
  Get,
  ParseBoolPipe,
  Query,
} from '@nestjs/common';

@Controller('users')
export class LeaderboardUserController {

  @Get()
  async getAll(
    @Query('hideUsernames', ParseBoolPipe) hideUsernames: boolean,
  ) {
    return "data";
  }
}

Expected behavior

Endpoints returns "data".

Other

No response

[micalevisk]

that's expected and it was a breaking change, as I described in that PR. That's why it was introduced in v10, not in v9

you should supply a default value, like with the others pipe

[micalevisk]

btw that has nothing to do with ValidationPipe

it just for ParseBoolPipe

[myfunc]

I wonder how many unexpected runtime issues like this I will face in v10.

[micalevisk]

migration guide docs.nestjs.com/migration-guide and is not highlighted in the release notes.

feel free to add it in that page

[myfunc]

Actually thank you, now I see the full list of such possible changes. Thank you for a quick response.

[micalevisk]

@myfunc

actually, in your case, you should see a validation error (400 bad request), not undefined, right? because ParseBoolPipe is expecting a boolean value

can you provide a minimum repro?

[myfunc]

Yes, I see a validation error.
I think there is no need to make a minimal repo for that listed change. That's completely clear now.

[myfunc]

That's risky breaking change, cause it reveals only in runtime.