Field encoding

django/db/migrations/writer.py

 import datetime
 import types
+from django.db import models
 
 
 class MigrationWriter(object):
@@ -85,6 +86,25 @@ class MigrationWriter(object):
         # Simple types
         elif isinstance(value, (int, long, float, str, unicode, bool, types.NoneType)):
             return repr(value), set()
+        # Django fields
+        elif isinstance(value, models.Field):
+            attr_name, path, args, kwargs = value.deconstruct()
+            module, name = path.rsplit(".", 1)
+            if module == "django.db.models":
+                imports = set()
+            else:
+                imports = set("import %s" % module)
+                name = path
+            arg_strings = []
+            for arg in args:
+                arg_string, arg_imports = cls.serialize(arg)
+                arg_strings.append(arg_string)
+                imports.update(arg_imports)
+            for kw, arg in kwargs.items():
+                arg_string, arg_imports = cls.serialize(arg)
+                imports.update(arg_imports)
+                arg_strings.append("%s=%s" % (kw, arg_string))
+            return "%s(%s)" % (name, ", ".join(arg_strings)), imports
         # Functions
         elif isinstance(value, (types.FunctionType, types.BuiltinFunctionType)):
             # Special-cases, as these don't have im_class

tests/migrations/test_writer.py

@@ -2,7 +2,7 @@
 import datetime
 from django.test import TransactionTestCase
 from django.db.migrations.writer import MigrationWriter
-from django.db import migrations
+from django.db import models, migrations
 
 
 class WriterTests(TransactionTestCase):
@@ -56,6 +56,7 @@ class WriterTests(TransactionTestCase):
         migration = type("Migration", (migrations.Migration,), {
             "operations": [
                 migrations.DeleteModel("MyModel"),
+                migrations.AddField("OtherModel", "field_name", models.DateTimeField(default=datetime.datetime.utcnow))
             ],
             "dependencies": [("testapp", "some_other_one")],
         })