Using form.onPart() to validate file type/name and then form.parse to receive the file

Should I be able to use form.onPart() along with form.parse() in order to

form.onPart(): test for valid file types and return validation message if that fails or continue on to…

form.parse(): parse the file if the validation in form.onPart() passes?

I can’t seem to find the right way to do this.

CONTROLLER:

class {
  public initializeRoutes() {
    this.router.post(
      '/file',
      this.uploadFile,
    );
  }
  formidableOptions = {
    encoding: 'utf-8',
    keepExtensions: true,
    // 3 mb for news image and attachments. override otherwise
    maxFileSize: 3 * 1024 * 1024,
  };

  uploadFile = (req: Request, res: Response) => {
    const typeValidationMessage = 'Please choose a JPEG, GIF, PDF or DOC file.';

    const form = formidable(this.formidableOptions);

    form.onPart = (part: { filename: any; mime: any }) => {
      let isValid = true;
      if (part.filename || part.mime) {
        if (part.filename) {
          isValid =
            isValid && !AttachmentValidator.isInvalidFileName(part.filename);
        }

        if (part.mime) {
          isValid =
            isValid && !AttachmentValidator.isInvalidFileType(part.mime);
        }
        if (!isValid) {
          return res.status(400).json({ message: typeValidationMessage });
        }
      }
    };

    try {
      UploadService.upload(
        req,
        // onSuccess callback
        async (fileLocation: string, originalName: string) => {
          try {
            await C3DistributionService.sendAttachment(
              fileLocation,
              originalName,
            );
          } catch (error) {
            this.logger.error(error);
            return res.status(500).json({ message: error.message });
          } finally {
            // try catch swallow in case only the delete tmp file (unlinkSync) fails
            try {
              fs.unlinkSync(fileLocation);
            } catch (error) {
              this.logger.error(error);
            }
          }
          return res.status(201).send();
        },
        // onFail callback
        () => {
          return res.status(500).json({
            message: 'unexpected error from upload service callback run',
          });
        },
      );
    } catch (error) {
      this.logger.error(error);
      return res.status(500).json({ message: error.message });
    }
  };
}

SERVICE/formidable parse wrapper:

const formidableOptions = {
  encoding: 'utf-8',
  uploadDir: UPLOAD_DIR,
  keepExtensions: true,
  // 3 mb for news image and attachments. override otherwise
  maxFileSize: 3 * 1024 * 1024,
};

const UploadService = {
  upload: (req: Request, onSuccess?: Function, onFail?: Function): void => {
    ensureTmpFilePath();

    const form = formidable(formidableOptions);

    form.parse(req, (err: any, fields: any, files: { files: File }) => {
      if (err) {
        logger.error('formidable err: %j', err);
        if (onFail) {
          onFail();
        }
      } else if (onSuccess) {
        onSuccess(files.files.path, files.files.name);
      }
    });
  },
};

_Originally posted by @droddy in https://github.com/node-formidable/formidable/issues/387#issuecomment-620767478_ EDIT: SYNTAX highlighting

[FlorentinTh]

@droddy multer let you do this also, you have a nice fileFilter function that let you control each file before they are uploaded. Also if you want to check more seriously the type of file users of yours are uploading I suggest using multer configured with an in memory storage, then in the callback that can be directly set in your middleware, you can verify the magic number of files thanks to a package like file-type and if they satisfy your requirements, write them to the disk simply through fs.writeFile since you have access to the buffer of the file inside multer’s callback.

@tunnckoCore integrate all of this in a nice v2 of formidable should be pretty formidable 😊

PS: I’m not promoting anything here, just give you some options to complete what you want.

[droddy]

Thanks! I’ll give it a shot.

I think I’m about to try to become a contributor BTW! I think I could help improve documentation for a start.