add default coerce to any Select2Field

[samialfattani]

run-time error is raised if Select2Field did'nt include coerce=int in form_args

Here is how to replicate the error

  class Model2(db.Model):  
      def __init__(self,int_field=None):
          self.int_field = int_field

      int_field = Column(Integer)

  class MyModelView(ModelView):
      form_columns = ["int_field"]
      form_choices = {"int_field": [("101", "101"), ("150", "150")]}
      form_args = {
          "int_field": {"validators": [NumberRange(min=100, max=199)]},
      }

This PR adds a default coerce function if it is not provided explicitly based on the Column's type

the added tests won't pass without changes in this PR

[ElLorans]

Why do you need to change typing? Do we need to change all other orm libraries?

[samialfattani]

Why do you need to change typing? Do we need to change all other orm libraries?

what do you mean? i'm not changing the typing. This PR just extract the right coerce function that match the Column's type.

[ElLorans]

I think we can simply add coerce to T_FIELD_ARGS_VALIDATORS and remove T_FIELD_ARGS_VALIDATORS_SELECTABLE

[samialfattani]

I think we can simply add coerce to T_FIELD_ARGS_VALIDATORS and remove T_FIELD_ARGS_VALIDATORS_SELECTABLE

I've tried your suggestion but unfortunately it all fields that don't include coerce attr. will be affected and raise typing issues. I believe T_FIELD_ARGS_VALIDATORS_SELECTABLE is more clear and dedicated to SELECT fields

[ElLorans]

Sorry, let me be more specific. Why not editing T_FIELD_ARGS_VALIDATORS_ALLOW_BLANK

[samialfattani]

Sorry, let me be more specific. Why not editing T_FIELD_ARGS_VALIDATORS_ALLOW_BLANK

the T_FIELD_ARGS_VALIDATORS_ALLOW_BLANK is being used in other 2 functions _get_description and _convert_relation and i don't want those funcitons to be harmed if just edit it. but any i can have a try if you say so.

[ElLorans]

Does this PR only make it work for sqlalchemy? Or other libraries do not have this issue?

[samialfattani]

it is tested only in Sqlalchemy, however, i've tried to add a Peewee test but it seems like there is no way to use coerce function in Peewee or Pymongo