Image File Upload via REST case Error 500 response due destination directory not set

Question

I'm struggling to upload images to the Drupal 8 site via REST. Finally, I managed to deliver the file to the server, but then the error 500 rased due destination folder not set. I can't figure where to define this destination directory: in request JSON data or header, or somewhere else in the settings.php or somewhere in REST configuration?

Here my code in Python:

def create_drupal_image(session, oauth, media_name, image_path):
    file_size = os.stat(image_path).st_size
    with open(image_path, "rb") as image_file:
        encoded_string = base64.b64encode(image_file.read())

    payload = {
        "filename": [
            {
                "value": media_name + ".jpg"
            }
        ],
        "filemime": [
            {
                "value": "image/jpeg"
            }
        ],
        "filesize": [
            {
                "value": str(file_size)
            }
        ],
        "type": [
            {
                "target_id": "image"
            }
        ],
        "data": [
            {
                "value": "data:image/jpeg;base64," + str(encoded_string)
            }
        ],
        "_links": {
            "type": {
                "href": oauth.base_url + REST_TYPE_FILE_IMAGE
            },
        }
    }
    return create_drupal_entity_impl(session, oauth, ENTITY_FILE_URL, payload)


def create_drupal_entity_impl(session, oauth, url, payload):
    payload_str = json.dumps(payload)
    # print(payload_str)
    endpoint = oauth.base_url + url
    # Set all required headers
    headers = {
        'Content-Type': 'application/hal+json',
        'Accept': 'application/hal+json',
        'Authorization': 'Bearer ' + oauth.access_token
    }
    # Post the new node (a Contact) to the endpoint.
    response = session.post(endpoint, data=payload_str, headers=headers, verify=oauth.verify)
    return handle_create_response(response)

Edited this source core/lib/Drupal/Core/File/FileSystem.php line 488 in order to print the $destination, and it appears to be empty. See '' in the server log below:

AH01071: Got error 'PHP message: Uncaught PHP Exception Drupal\\Core\\File\\Exception
\\DirectoryNotReadyException: "The specified file 'temporary://filemDIAwD' could not be copied 
because the destination '' directory is not properly configured. This may be caused by a problem 
with file or directory permissions." at /var/www/vhosts/web.site/core/lib/Drupal/Core/File
/FileSystem.php line 488'

Tried to define 'file_private_path' folder in settings.php, added 'tmp' folder under 'sites/default/files' but with no result. What am I missing here?

Answer 1

The missing property was destination "uri"

"uri": [
   {
      "value": "public://" + media_name + ".jpg"
   }
],