Fixed #21275 -- Fixed a serializer error when generating migrations for contrib.auth.

The migration serializer now looks for a deconstruct method on any object.

1 files changed, 35 insertions, 0 deletions

diff --git a/django/utils/deconstruct.py b/django/utils/deconstruct.py
new file mode 100644
index 0000000000..7774e69997
--- /dev/null
+++ b/django/utils/deconstruct.py
@@ -0,0 +1,35 @@
+def deconstructible(*args, **kwargs):
+    """
+    Class decorator that allow the decorated class to be serialized
+    by the migrations subsystem.
+
+    Accepts an optional kwarg `path` to specify the import path.
+    """
+    path = kwargs.pop('path', None)
+
+    def decorator(klass):
+        def __new__(cls, *args, **kwargs):
+            # We capture the arguments to make returning them trivial
+            obj = super(klass, cls).__new__(cls)
+            obj._constructor_args = (args, kwargs)
+            return obj
+
+        def deconstruct(obj):
+            """
+            Returns a 3-tuple of class import path, positional arguments,
+            and keyword arguments.
+            """
+            return (
+                path or '%s.%s' % (obj.__class__.__module__, obj.__class__.__name__),
+                obj._constructor_args[0],
+                obj._constructor_args[1],
+            )
+
+        klass.__new__ = staticmethod(__new__)
+        klass.deconstruct = deconstruct
+
+        return klass
+
+    if not args:
+        return decorator
+    return decorator(*args, **kwargs)