NestJS Filters with Swagger deepObject (example: `?filters[name]=thing1&filters[description]=thing2`)

api-filter-query.ts

import { applyDecorators } from '@nestjs/common';
import { ApiExtraModels, ApiQuery, getSchemaPath } from '@nestjs/swagger';

/**
 * Combines Swagger Decorators to create a description for `filters[name]=something`
 *  - has support for swagger
 *  - automatic transformation with nestjs
 */
// eslint-disable-next-line @typescript-eslint/ban-types,@typescript-eslint/explicit-module-boundary-types
export function ApiFilterQuery(fieldName: string, filterDto: Function) {
  return applyDecorators(
    ApiExtraModels(filterDto),
    ApiQuery({
      required: false,
      name: fieldName,
      style: 'deepObject',
      explode: true,
      type: 'object',
      schema: {
        $ref: getSchemaPath(filterDto),
      },
    }),
  );
}

example.ts

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

import { ApiFilterQuery } from './api-filter-query';

import { ApiPropertyOptional } from '@nestjs/swagger';
import { IsOptional, IsString } from 'class-validator';

class ThingFiltersDto {
  @ApiPropertyOptional({ description: 'Thing Name', example: 'Ficus' })
  @IsString()
  @IsOptional()
  readonly name?: string;

  @ApiPropertyOptional({ description: 'Thing Description', example: 'Large' })
  @IsString()
  @IsOptional()
  readonly description?: string;
}

@Controller()
export class FlowerController {
  @Get('things')
  @ApiOperation({ summary: ' List/Filter' })
  @ApiFilterQuery('filters', ThingFiltersDto)
  async list(@Query('filters') filters: ThingFiltersDto): Promise<void> {
    console.log({ filters });
    // from: filters[name]=thing1&filters[description]=thing2 
    // to: { name: "thing1", description: "thing2"
  }
}

Hello @MarZab
Here is an improvement of your initial idea, such decorator accepts a class and extracts all properties and corresponding types

import { applyDecorators } from '@nestjs/common';
import { ApiExtraModels, ApiQuery, getSchemaPath } from '@nestjs/swagger';

// eslint-disable-next-line @typescript-eslint/ban-types,@typescript-eslint/explicit-module-boundary-types
export function ApiNestedQuery(query: Function) {
  const constructor = query.prototype;
  const properties = Reflect
      .getMetadata('swagger/apiModelPropertiesArray', constructor)
      .map(prop => prop.substr(1));

  const decorators = properties.map(property => {
    const propertyType = Reflect.getMetadata('design:type', constructor, property);
    return [
      ApiExtraModels(propertyType),
      ApiQuery({
        required: false,
        name: property,
        style: 'deepObject',
        explode: true,
        type: 'object',
        schema: {
          $ref: getSchemaPath(propertyType),
        },
      })
    ]
  }).flat();

  return applyDecorators(...decorators);
}

perfect!

Thank you @MarZab for this very useful example!

To avoid the "eslint-disable-next-line", we can use Type from @nestjs/common instead of Function.

I can't figure out how to use ApiNestedQuery decorator @gwythyr