file upload schema error 400

Hi, when i define the schema consumer in endpoint /upload to ‘multipart/form-data’ for uploading file i dont know wich is the schema structure body for passing the base64 string or the file that i need to upload.

If y define the schema:

schema: {
      description: 'Upload file',
      tags: ['Info'],
      consumes: [ 'multipart/form-data' ],
      summary: 'Upload the file to the server',
      body: {
        type: 'object',
        properties: {
          file: {type: 'string'}
        }
      },
      response: {
        200: {
          description: 'Succesful response',
          type: 'boolean'
        }
      }
    }

when i send the post get the error:

{
  "statusCode": 400,
  "error": "Bad Request",
  "message": "body should be object"
}

I fetch in the dynamic.js code looking for the solution but i dont get with it.

Can you help me?

PD: Im sorry if this is not the place for this kind of issues.

Thx

[kristofferostlund]

I found another workaround based on @SkeLLLa’s suggestion, where I add a small ajv plugin to fastify, which I believe might be a little bit less intrusive?

Below is a fully functioning example:

const Fastify = require('fastify') // 2.11.0
const multer = require('fastify-multer') // 1.5.2
const swagger = require('fastify-swagger') // 2.5.0
const uploads = multer({ dest: '/tmp/file-uploads' })

function ajvPlugin(ajv, options) {
  ajv.addKeyword('isFileType', {
    compile: (schema, parent, it) => {
      // Change the schema type, as this is post validation it doesn't appear to error.
      parent.type = 'file'
      delete parent.isFileType
      return () => true
    },
  })

  return ajv
}

const fastify = Fastify({ logger: true, ajv: { plugins: [ajvPlugin] } })

fastify.register(multer.contentParser, { addToBody: true })
fastify.register(swagger, { exposeRoute: true })

fastify.post('/uploads', {
  schema: {
    consumes: ['multipart/form-data'],
    body: { properties: { file_1: { isFileType: true } } },
    // Shortened for the example
  },
  preHandler: uploads.single('file_1'),
  handler: async (req, reply) => req.file,
})

fastify.listen(3000)

[SkeLLLa]

Here’s another workaround.

First of all as it was mentioned above we should add custom binary format:

const fastify = require('fastify')();
// ...
const ajv = new Ajv({
  // the fastify defaults (if needed)
  removeAdditional: true,
  useDefaults: true,
  coerceTypes: true,
  allErrors: true,
  nullable: true,
});
fastify.setSchemaCompiler(function(schema) {
  ajv.addFormat('binary', () => {
    // here you can do some additional checks
    return true;
  });
  return ajv.compile(schema);
});

Afterwards in your routes we should do some hack that will allow to pass ajv validation for string type. So we need preValidation hook where we’ll replace what’s come from user with some string, so ajv will validate it and hide original file inside non-enumerable property.

fastify.post(
    '/',
    {
      preValidation: async (req) => {
        const file = {...req.body.file};
        req.body.file = '@file';
        req.body[Symbol.for('file')] = file;
      },
      schema: {
        description: `create new file`,
        tags: ['files'],
        summary: 'create file',
        consumes: ['multipart/form-data'],
        body: {
          type: 'object',
          properties: {
            file: {
              type: 'string',
              format: 'binary',
            },
          },
        },
        response: {
         '200': { description: 'ok' },
        },
      },
    },
    async (request, reply) => {
      const files = request.body[Symbol.for('file')];
      // do something with your files.
    }
  );