schema-evolution: update from HEAD (v5821)

git-svn-id: http://code.djangoproject.com/svn/django/branches/schema-evolution@5822 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 67 insertions, 0 deletions

diff --git a/django/utils/maxlength.py b/django/utils/maxlength.py
new file mode 100644
index 0000000000..9216fe1c3a
--- /dev/null
+++ b/django/utils/maxlength.py
@@ -0,0 +1,67 @@
+"""
+Utilities for providing backwards compatibility for the maxlength argument,
+which has been replaced by max_length, see ticket #2101.
+"""
+
+from warnings import warn
+
+def get_maxlength(self):
+    return self.max_length
+
+def set_maxlength(self, value):
+    self.max_length = value
+
+def legacy_maxlength(max_length, maxlength):
+    """
+    Consolidates max_length and maxlength, providing backwards compatibilty
+    for the legacy "maxlength" argument.
+    If one of max_length or maxlength is given, then that value is returned.
+    If both are given, a TypeError is raised.
+    If maxlength is used at all, a deprecation warning is issued.
+    """
+    if maxlength is not None:
+        warn("maxlength is deprecated, use max_length instead.",
+             PendingDeprecationWarning,
+             stacklevel=3)
+        if max_length is not None:
+            raise TypeError("field can not take both the max_length"
+                            " argument and the legacy maxlength argument.")
+        max_length = maxlength
+    return max_length
+
+def remove_maxlength(func):
+    """
+    A decorator to be used on a class's __init__ that provides backwards
+    compatibilty for the legacy "maxlength" keyword argument, i.e.
+      name = models.CharField(maxlength=20)
+    It does this by changing the passed "maxlength" keyword argument
+    (if it exists) into a "max_length" keyword argument.
+    """
+    def inner(self, *args, **kwargs):
+        max_length = kwargs.get('max_length', None)
+        # pop maxlength because we don't want this going to __init__.
+        maxlength = kwargs.pop('maxlength', None)
+        max_length = legacy_maxlength(max_length, maxlength)
+        # Only set the max_length keyword argument if we got a value back.
+        if max_length is not None:
+            kwargs['max_length'] = max_length
+        func(self, *args, **kwargs)
+    return inner
+
+# This metaclass is used in two places, and should be removed when legacy
+# support for maxlength is dropped.
+#   * oldforms.FormField
+#   * db.models.fields.Field
+
+class LegacyMaxlength(type):
+    """
+    Metaclass for providing backwards compatibility support for the
+    "maxlength" keyword argument.
+    """
+
+    def __init__(cls, name, bases, attrs):
+        super(LegacyMaxlength, cls).__init__(name, bases, attrs)
+        # Decorate the class's __init__ to remove any maxlength keyword.
+        cls.__init__ = remove_maxlength(cls.__init__)
+        # Support accessing and setting to the legacy maxlength attribute.
+        cls.maxlength = property(get_maxlength, set_maxlength)