TypedFormData.Body with fastify

[tjhiggins]

Feedback

I upgraded to the latest version of nestia and wasn't thrilled about having to use fastify-multer with TypedFormData.Body. Since fastify-multer is just an unmaintained port that was last published 3 years ago.

I wanted to keep using @fastify/multipart so I hacked around and got it working how I wanted with nestia. Figured I'd share since I think the new interface is less desirable for fastify users.

The nice part is that it uses the normal nestjs body and the validation pipes apply to it because of attachFieldsToBody. Obviously super hacky, but maybe you could add first class support for @fastify/multipart? Also please let me know if there was a better way.

export type FileUpload = {
  name: string;
  type: string;
  value: Buffer;
};

// main.ts
import multipart from "@fastify/multipart";

app.register(multipart, {
  attachFieldsToBody: "keyValues",
  onFile: async (part) => {
    const file: FileUpload = {
      name: part.filename,
      type: part.mimetype,
      value: await part.toBuffer(),
    };
    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
    // @ts-expect-error
    part.value = file;
  },
});

// dto.ts
export class ExampleDto {
  @IsDefined()
  file: FileUpload;

  @IsString()
  name: string;
}

// controller.ts
@Post('/example')
@SwaggerCustomizerFile()
async uploadFile(@Body() dto: ExampleDto) {
  console.log(dto.file)
}

// swagger.ts (super hacky)
import { SwaggerCustomizer } from '@nestia/core';

export function SwaggerCustomizerFile() {
  return function (target: any, propertyKey: string, descriptor: PropertyDescriptor) {
    SwaggerCustomizer((props: SwaggerCustomizer.IProps) => {
      const neighbor = props.at(descriptor.value);
      const content = neighbor?.route.requestBody?.content;
      if (content) {
        const oldValue = content['application/json'];

        const schema = oldValue?.schema;
        if (schema && '$ref' in schema) {
          const componentName = schema['$ref'].split('/').pop()!;
          const component = props.swagger.components.schemas![componentName];

          if ('properties' in component && component.properties?.file) {
            component.properties.file = { type: 'file' } as any;
          }
        }

        delete content['application/json'];
        content['multipart/form-data'] = oldValue;
      }
    })(target, propertyKey, descriptor);
  };
}

[tjhiggins]

The best case scenario for me would be if nestia was okay with having the File type in a dto. Also it would update the content type to be multipart/form-data if a file type existed in the dto.

export class ExampleDto {
  @IsDefined()
  file: File;

  @IsString()
  name: string;
}