Allow `missing_value` without setting `min` and `max`

Fixes #9

Note that you must still specify a `default` in that case. I'm not
sure that makes sense or not.

This impacts Int, Float, Decimal, DateTime, Timedelta, Date, and
Time---all the subclasses of Orderable. They all have a test case.

Also fix ValidatedProperty and DefaultProperty to do the right thing
when accessesd on the class and not the instance (which is to return
themself; previously they would raise AttributeError).

3 files changed, 75 insertions, 27 deletions

diff --git a/src/zope/schema/_bootstrapfields.py b/src/zope/schema/_bootstrapfields.py
index e16d138..5c318e7 100644
--- a/src/zope/schema/_bootstrapfields.py
+++ b/src/zope/schema/_bootstrapfields.py
@@ -40,31 +40,35 @@ from zope.schema._schema import getFields
 
 class ValidatedProperty(object):
 
-    def __init__(self, name, check=None):
-        self._info = name, check
+    def __init__(self, name, check=None, allow_none=False):
+        self._name = name
+        self._check = check
+        self._allow_none = allow_none
 
     def __set__(self, inst, value):
-        name, check = self._info
-        if value != inst.missing_value:
-            if check is not None:
-                check(inst, value)
+        bypass_validation = (value is None and self._allow_none) or value == inst.missing_value
+        if not bypass_validation:
+            if self._check is not None:
+                self._check(inst, value)
             else:
                 inst.validate(value)
-        inst.__dict__[name] = value
+        inst.__dict__[self._name] = value
 
     def __get__(self, inst, owner):
-        name, check = self._info
-        return inst.__dict__[name]
+        if inst is None:
+            return self
+        return inst.__dict__[self._name]
 
 
 class DefaultProperty(ValidatedProperty):
 
     def __get__(self, inst, owner):
-        name, check = self._info
+        if inst is None:
+            return self
         defaultFactory = inst.__dict__.get('defaultFactory')
         # If there is no default factory, simply return the default.
         if defaultFactory is None:
-            return inst.__dict__[name]
+            return inst.__dict__[self._name]
         # Get the default value by calling the factory. Some factories might
         # require a context to produce a value.
         if IContextAwareDefaultFactory.providedBy(defaultFactory):
@@ -72,8 +76,8 @@ class DefaultProperty(ValidatedProperty):
         else:
             value = defaultFactory()
         # Check that the created value is valid.
-        if check is not None:
-            check(inst, value)
+        if self._check is not None:
+            self._check(inst, value)
         elif value != inst.missing_value:
             inst.validate(value)
         return value
@@ -279,8 +283,8 @@ class Orderable(object):
     Orderable is a mixin used in combination with Field.
     """
 
-    min = ValidatedProperty('min')
-    max = ValidatedProperty('max')
+    min = ValidatedProperty('min', allow_none=True)
+    max = ValidatedProperty('max', allow_none=True)
 
     def __init__(self, min=None, max=None, default=None, **kw):
 
diff --git a/src/zope/schema/tests/test__bootstrapfields.py b/src/zope/schema/tests/test__bootstrapfields.py
index 75a5166..30b9126 100644
--- a/src/zope/schema/tests/test__bootstrapfields.py
+++ b/src/zope/schema/tests/test__bootstrapfields.py
@@ -741,7 +741,29 @@ class BoolTests(unittest.TestCase):
         self.assertEqual(txt.fromUnicode(u'true'), True)
 
 
-class IntTests(unittest.TestCase):
+class OrderableMissingValueMixin(object):
+
+    mvm_missing_value = -1
+    mvm_default = 0
+
+    def test_missing_value_no_min_or_max(self):
+        # We should be able to provide a missing_value without
+        # also providing a min or max. But note that we must still
+        # provide a default.
+        # See https://github.com/zopefoundation/zope.schema/issues/9
+        Kind = self._getTargetClass()
+        self.assertTrue(Kind.min._allow_none)
+        self.assertTrue(Kind.max._allow_none)
+
+        field = self._makeOne(missing_value=self.mvm_missing_value,
+                              default=self.mvm_default)
+        self.assertIsNone(field.min)
+        self.assertIsNone(field.max)
+        self.assertEqual(self.mvm_missing_value, field.missing_value)
+
+
+class IntTests(OrderableMissingValueMixin,
+               unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._bootstrapfields import Int
diff --git a/src/zope/schema/tests/test__field.py b/src/zope/schema/tests/test__field.py
index 6b8384e..0758c42 100644
--- a/src/zope/schema/tests/test__field.py
+++ b/src/zope/schema/tests/test__field.py
@@ -11,8 +11,11 @@
 # FOR A PARTICULAR PURPOSE.
 #
 ##############################################################################
+import datetime
+import decimal
 import unittest
 
+from zope.schema.tests.test__bootstrapfields import OrderableMissingValueMixin
 
 class BytesTests(unittest.TestCase):
 
@@ -249,7 +252,11 @@ class ASCIILineTests(unittest.TestCase):
         self.assertEqual(field.constraint('abc\ndef'), False)
 
 
-class FloatTests(unittest.TestCase):
+class FloatTests(OrderableMissingValueMixin,
+                 unittest.TestCase):
+
+    mvm_missing_value = -1.0
+    mvm_default = 0.0
 
     def _getTargetClass(self):
         from zope.schema._field import Float
@@ -326,7 +333,11 @@ class FloatTests(unittest.TestCase):
         self.assertEqual(flt.fromUnicode(u'1.23e6'), 1230000.0)
 
 
-class DecimalTests(unittest.TestCase):
+class DecimalTests(OrderableMissingValueMixin,
+                   unittest.TestCase):
+
+    mvm_missing_value = decimal.Decimal("-1")
+    mvm_default = decimal.Decimal("0")
 
     def _getTargetClass(self):
         from zope.schema._field import Decimal
@@ -346,7 +357,6 @@ class DecimalTests(unittest.TestCase):
         verifyObject(IDecimal, self._makeOne())
 
     def test_validate_not_required(self):
-        import decimal
         field = self._makeOne(required=False)
         field.validate(decimal.Decimal("10.0"))
         field.validate(decimal.Decimal("0.93"))
@@ -354,7 +364,6 @@ class DecimalTests(unittest.TestCase):
         field.validate(None)
 
     def test_validate_required(self):
-        import decimal
         from zope.schema.interfaces import RequiredMissing
         field = self._makeOne()
         field.validate(decimal.Decimal("10.0"))
@@ -363,7 +372,6 @@ class DecimalTests(unittest.TestCase):
         self.assertRaises(RequiredMissing, field.validate, None)
 
     def test_validate_min(self):
-        import decimal
         from zope.schema.interfaces import TooSmall
         field = self._makeOne(min=decimal.Decimal("10.5"))
         field.validate(decimal.Decimal("10.6"))
@@ -372,7 +380,6 @@ class DecimalTests(unittest.TestCase):
         self.assertRaises(TooSmall, field.validate, decimal.Decimal("10.4"))
 
     def test_validate_max(self):
-        import decimal
         from zope.schema.interfaces import TooBig
         field = self._makeOne(max=decimal.Decimal("10.5"))
         field.validate(decimal.Decimal("5.3"))
@@ -381,7 +388,6 @@ class DecimalTests(unittest.TestCase):
         self.assertRaises(TooBig, field.validate, decimal.Decimal("20.7"))
 
     def test_validate_min_and_max(self):
-        import decimal
         from zope.schema.interfaces import TooBig
         from zope.schema.interfaces import TooSmall
         field = self._makeOne(min=decimal.Decimal("-0.6"),
@@ -410,7 +416,11 @@ class DecimalTests(unittest.TestCase):
         self.assertEqual(flt.fromUnicode(u'12345.6'), Decimal('12345.6'))
 
 
-class DatetimeTests(unittest.TestCase):
+class DatetimeTests(OrderableMissingValueMixin,
+                    unittest.TestCase):
+
+    mvm_missing_value = datetime.datetime.now()
+    mvm_default = datetime.datetime.now()
 
     def _getTargetClass(self):
         from zope.schema._field import Datetime
@@ -496,7 +506,11 @@ class DatetimeTests(unittest.TestCase):
         self.assertRaises(TooBig, field.validate, d5)
 
 
-class DateTests(unittest.TestCase):
+class DateTests(OrderableMissingValueMixin,
+                unittest.TestCase):
+
+    mvm_missing_value = datetime.date.today()
+    mvm_default = datetime.date.today()
 
     def _getTargetClass(self):
         from zope.schema._field import Date
@@ -586,7 +600,11 @@ class DateTests(unittest.TestCase):
         self.assertRaises(TooBig, field.validate, d5)
 
 
-class TimedeltaTests(unittest.TestCase):
+class TimedeltaTests(OrderableMissingValueMixin,
+                     unittest.TestCase):
+
+    mvm_missing_value = datetime.timedelta(minutes=15)
+    mvm_default = datetime.timedelta(minutes=12)
 
     def _getTargetClass(self):
         from zope.schema._field import Timedelta
@@ -656,7 +674,11 @@ class TimedeltaTests(unittest.TestCase):
         self.assertRaises(TooBig, field.validate, t5)
 
 
-class TimeTests(unittest.TestCase):
+class TimeTests(OrderableMissingValueMixin,
+                unittest.TestCase):
+
+    mvm_missing_value = datetime.time(12, 15, 37)
+    mvm_default = datetime.time(12, 25, 42)
 
     def _getTargetClass(self):
         from zope.schema._field import Time