fix mongoengine model converter

flask_admin/contrib/mongoengine/form.py

@@ -7,6 +7,7 @@ from flask_mongoengine.wtf import orm, fields as mongo_fields
 from flask_admin import form
 from flask_admin.model.form import FieldPlaceholder
 from flask_admin.model.fields import InlineFieldList, AjaxSelectField, AjaxSelectMultipleField
+from flask_admin.form.validators import FieldListInputRequired
 from flask_admin._compat import iteritems
 
 from .fields import ModelFormField, MongoFileField, MongoImageField
@@ -74,7 +75,10 @@ class CustomModelConverter(orm.ModelConverter):
             kwargs['validators'] = list(kwargs['validators'])
 
         if field.required:
-            kwargs['validators'].append(validators.InputRequired())
+            if isinstance(field, ListField):
+                kwargs['validators'].append(FieldListInputRequired())
+            else:
+                kwargs['validators'].append(validators.InputRequired())
         elif not isinstance(field, ListField):
             kwargs['validators'].append(validators.Optional())
 

flask_admin/form/validators.py

+from flask_admin.babel import gettext
+
+from wtforms.validators import StopValidation
+
+
+class FieldListInputRequired(object):
+    """
+        Validates that at least one item was provided for a FieldList
+    """
+
+    field_flags = ('required',)
+
+    def __call__(self, form, field):
+        if len(field.entries) == 0:
+            field.errors[:] = []
+            raise StopValidation(gettext('This field requires at least one item.'))

flask_admin/helpers.py

@@ -45,13 +45,15 @@ def get_url(endpoint, **kwargs):
 
 def is_required_form_field(field):
     """
-        Check if form field has `DataRequired` or `InputRequired` validators.
+        Check if form field has `DataRequired`, `InputRequired`, or
+        `FieldListInputRequired` validators.
 
         :param field:
             WTForms field to check
     """
+    from flask_admin.form.validators import FieldListInputRequired
     for validator in field.validators:
-        if isinstance(validator, (DataRequired, InputRequired)):
+        if isinstance(validator, (DataRequired, InputRequired, FieldListInputRequired)):
             return True
     return False