Lazily import sqlalchemy_utils and arrow.

flask_admin/contrib/sqla/form.py

@@ -4,7 +4,6 @@ from enum import Enum, EnumMeta
 from wtforms import fields, validators
 from sqlalchemy import Boolean, Column
 from sqlalchemy.orm import ColumnProperty
-from sqlalchemy_utils import Choice
 
 from flask_admin import form
 from flask_admin.model.form import (converts, ModelConverterBase,
@@ -428,6 +427,8 @@ def choice_type_coerce_factory(type_):
     Return a function to coerce a ChoiceType column, for use by Select2Field.
     :param type_: ChoiceType object
     """
+    from sqlalchemy_utils import Choice
+
     choices = type_.choices
     if isinstance(choices, type) and issubclass(choices, Enum):
         key, choice_cls = 'value', choices

flask_admin/contrib/sqla/typefmt.py

 from sqlalchemy.ext.associationproxy import _AssociationList
 
 from flask_admin.model.typefmt import BASE_FORMATTERS, EXPORT_FORMATTERS, \
-    DETAIL_FORMATTERS, list_formatter
+    list_formatter
 from sqlalchemy.orm.collections import InstrumentedList
-from sqlalchemy_utils import Choice
-from arrow import Arrow
 
 
 def choice_formatter(view, choice):
@@ -42,15 +40,20 @@ def arrow_export_formatter(view, arrow_time):
 
 DEFAULT_FORMATTERS = BASE_FORMATTERS.copy()
 EXPORT_FORMATTERS = EXPORT_FORMATTERS.copy()
-DETAIL_FORMATTERS = DETAIL_FORMATTERS.copy()
 
 DEFAULT_FORMATTERS.update({
     InstrumentedList: list_formatter,
     _AssociationList: list_formatter,
-    Choice: choice_formatter,
-    Arrow: arrow_formatter,
-})
-
-EXPORT_FORMATTERS.update({
-    Arrow: arrow_export_formatter,
 })
+try:
+    from sqlalchemy_utils import Choice
+    DEFAULT_FORMATTERS[Choice] = choice_formatter
+except ImportError:
+    pass
+    
+try:
+    from arrow import Arrow
+    DEFAULT_FORMATTERS[Arrow] = arrow_formatter
+    EXPORT_FORMATTERS[Arrow] = arrow_export_formatter
+except ImportError:
+    pass

flask_admin/contrib/sqla/validators.py

 from sqlalchemy.orm.exc import NoResultFound
-from sqlalchemy_utils import Currency
 
 from wtforms import ValidationError
 try:
@@ -70,6 +69,7 @@ class ItemsRequired(InputRequired):
 
 
 def valid_currency(form, field):
+    from sqlalchemy_utils import Currency
     try:
         Currency(field.data)
     except (TypeError, ValueError):

requirements-dev.txt

@@ -18,3 +18,5 @@ pylint
 sqlalchemy-citext
 sqlalchemy_utils
 azure-storage-blob
+arrow
+colour