Backported pallets-eco#266

CHANGES.rst

@@ -16,7 +16,14 @@ Unreleased
 -   Fixed broken format string in Arabic translation (`#471`_)
 -   Updated French and Japanese translations. (`#514`_, `#506`_)
 -   Updated Ukrainian translation (`#433`_)
-
+-   ``FieldList`` error list is keeps entries in orders for easier identifcation
+    of erroring fields (`#257`_, `#407`_)
+-   :class:`~validators.Length` gives a more helpful error message when
+    ``min`` and ``max`` are the same value (`#266`_)
+
+.. _#257: https://github.com/wtforms/wtforms/issues/257
+.. _#266: https://github.com/wtforms/wtforms/pull/266
+.. _#407: https://github.com/wtforms/wtforms/pull/407
 .. _#475: https://github.com/wtforms/wtforms/pull/475/
 .. _#463: https://github.com/wtforms/wtforms/pull/463
 .. _#523: https://github.com/wtforms/wtforms/pull/523

tests/validators.py

@@ -101,6 +101,7 @@ def test_length(self):
         self.assertEqual(length(min=6)(self.form, field), None)
         self.assertRaises(ValidationError, length(max=5), self.form, field)
         self.assertEqual(length(max=6)(self.form, field), None)
+        self.assertEqual(length(min=6, max=6)(self.form, field), None)
 
         self.assertRaises(AssertionError, length)
         self.assertRaises(AssertionError, length, min=5, max=2)
@@ -111,6 +112,7 @@ def test_length(self):
         self.assertTrue('at least 8' in grab(min=8))
         self.assertTrue('longer than 5' in grab(max=5))
         self.assertTrue('between 2 and 5' in grab(min=2, max=5))
+        self.assertTrue('exactly 5' in grab(min=5, max=5))
 
     def test_required(self):
         self.assertEqual(required()(self.form, DummyField('foobar')), None)

wtforms/validators.py

@@ -101,6 +101,9 @@ def __call__(self, form, field):
                 elif self.min == -1:
                     message = field.ngettext('Field cannot be longer than %(max)d character.',
                                              'Field cannot be longer than %(max)d characters.', self.max)
+                elif self.min == self.max:
+                    message = field.ngettext('Field must be exactly %(max)d character long.',
+                                             'Field must be exactly %(max)d characters long.', self.max)
                 else:
                     message = field.gettext('Field must be between %(min)d and %(max)d characters long.')