Flask WTForms -- custom field flags

Question

I built a custom validator that checks if a user input exists in a database. Now I want to add a custom field flag that pops up if the validation is not successful (without re-rendering html), similar to the 'required' flag in the InputRequired validator.

Here's my validator:

class ProjectExists(object):
    field_flags = ('project_not_exists', )   # need the custom flag here

    def __init__(self, project_code=None, message=None):
        self.project_code = project_code
        self.message = message
        self.conn, self.cur = connect_db()


    def __call__(self, form, field):
        code = field.data
        self.cur.execute("SELECT 1 FROM database WHERE project_code = '{}'".format(code))
        code_check = self.cur.fetchall()
        if not code_check:
            if self.message is None:
                self.message = field.gettext('Project code {} does not exists!'.format(code))
            raise StopValidation(self.message)

Here's the source code for the InputRequired validator for reference:

class InputRequired(object):
    field_flags = ('required', )

    def __init__(self, message=None):
        self.message = message


    def __call__(self, form, field):
        if not field.raw_data or not field.raw_data[0]:
            if self.message is None:
                message = field.gettext('This field is required.')
            else:
                message = self.message
                field.errors[:] = []
                raise StopValidation(message)

Appreciate your help!

Answer 1

Got it working with Parsley , checking against an existing endpoint if a project code exists.

WTForm:

class ViewForm(FlaskForm):
    project_code = StringField('Project Code',
                                render_kw={'required':"", 'data-parsley-project-check':""})

JavaScript:

$(function () {
  Parsley.addValidator('projectCheck', {
    validateString: function(value) {
      console.log("validating")
      var send = {
          id: value,
      }
      var url = '/projects/'
      return $.getJSON(url, send, function(data) {
      }).then(function(json) {
        if (!json['features']) {
        return $.Deferred().reject()
      }
    })
    },
    messages: {
      en: 'Project code does not exist!'
    }
  })})