fix: Boolean Type Transformation goes wrong

[somehowchris]

Description

Using @Type(() => Boolean does not work as advertised here.

Minimal code-snippet showcasing the problem
I have a minimal app to show the whole scenario https://github.com/somehowchris/nestjs-query-validation-failing

Doing:

curl --location --request POST 'http://localhost:3001/?name=Chris&external=false&age=12' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name":"Chris",
    "external": "false",
    "age": "12"
}'

Should transform "false" to the type Boolean with false

import { Type } from 'class-transformer';
import { IsBoolean, IsInt, IsPositive, IsString } from 'class-validator';

export class AppSearchQuery {
  @IsString()
  public name: string;
  @IsBoolean()
  @Type(() => Boolean)
  public external: boolean;
  @IsInt()
  @IsPositive()
  @Type(() => Number)
  public age: number;
}

Which again should result in the return body

{
    "name": "Chris",
    "external": false,
    "age": 12
}

but results in this

{
    "name": "Chris",
    "external": true,
    "age": 12
}

Expected behavior

The boolean should be transformed with its actual value.

Actual behavior

As shown the boolean value is true which should be false.

[diffy0712]

Hello @somehowchris,

This works as expected. Any non-empty string value is transformed to boolean true by Javascript.
You can force the 'correct' behavior, that you expect with a custom transformer.
Example:

@Transform(({ value }) => {
  if (value === 'true') return true;
  if (value === 'false') return false;
  return value;
})

There is a feature issue on allow casting of primitive values during transformation #550.

[github-actions]

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