CODE EXAMPLE FOR JAVASCRIPT

Upload literal unsupported graphql

import { UnsupportedMediaTypeException } from '@nestjs/common'
import { Scalar } from '@nestjs/graphql'
import { ValueNode } from 'graphql'
import { FileUpload, GraphQLUpload } from 'graphql-upload'

export type CSVParseProps = {
  file: FileUpload
  promise: Promise<FileUpload>
}

export type CSVUpload = Promise<FileUpload | Error>
export type CSVFile = FileUpload

@Scalar('CSV', () => CSV)
export class CSV {
  description = 'CSV upload type.'
  supportedFormats = ['text/csv']

  parseLiteral(arg: ValueNode) {
    const file = GraphQLUpload.parseLiteral(arg, (arg as any).value)

    if (
      file.kind === 'ObjectValue' &&
      typeof file.filename === 'string' &&
      typeof file.mimetype === 'string' &&
      typeof file.encoding === 'string' &&
      typeof file.createReadStream === 'function'
    )
      return Promise.resolve(file)

    return null
  }

  // If this is `async` then any error thrown
  // hangs and doesn't return to the user. However,
  // if a non-promise is returned it fails reading the
  // stream later. We can't evaluate the `sync`
  // version of the file either as there's a data race (it's not
  // always there). So we return the `Promise` version
  // for usage that gets parsed after return...
  parseValue(value: CSVParseProps) {
    return value.promise.then((file) => {
      if (!this.supportedFormats.includes(file.mimetype))
        return new UnsupportedMediaTypeException(
          `Unsupported file format. Supports: ${this.supportedFormats.join(
            ' '
          )}.`
        )

      return file
    })
  }

  serialize(value: unknown) {
    return GraphQLUpload.serialize(value)
  }
}