nestjs-typebox/src/interceptors.ts

This library provides helper utilities for writing and validating NestJS APIs using [TypeBox](https://github.com/sinclairzx81/typebox) as an alternative to class-validator/class-transformer. Can be configured to patch @nestjs/swagger allowing OpenAPI gene

import { CallHandler, ExecutionContext, Injectable, NestInterceptor } from '@nestjs/common';
import { Reflector } from '@nestjs/core';
import { DECORATORS } from '@nestjs/swagger/dist/constants.js';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';

import { isSchemaValidator } from './decorators.js';

@Injectable()
export class TypeboxTransformInterceptor implements NestInterceptor {
    constructor(private reflector: Reflector) {}

    intercept(context: ExecutionContext, next: CallHandler): Observable<unknown> {
        return next.handle().pipe(
            map(data => {
                const responseMeta = this.reflector.get(DECORATORS.API_RESPONSE, context.getHandler()) ?? {};
                const validator = (responseMeta['200'] || responseMeta['201'] || {})['type'];

                if (!isSchemaValidator(validator)) {
                    return data;
                }

                return validator.validate(data);
            })
        );
    }
}