From 2687fae6e99c026aef4e1b1c2b0e0507bd5dc61f Mon Sep 17 00:00:00 2001
From: Samuel Colvin <samcolvin@gmail.com>
Date: Wed, 6 Jun 2018 16:36:40 +0100
Subject: [PATCH] copy defaults to values, fix #154 (#192)

---
 HISTORY.rst        |  1 +
 pydantic/main.py   | 15 +++++++++------
 tests/test_main.py | 11 ++++++++++-
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/HISTORY.rst b/HISTORY.rst
index 141bb12..d0d391a 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -10,6 +10,7 @@ v0.10.0 (2018-XX-XX)
 * **breaking change**: removed ``Config.min_number_size`` and ``Config.max_number_size`` #183
 * added error context and ability to redefine error message templates using ``Config.error_msg_templates`` #183
 * fix typo in validator exception #150
+* copy defaults to model values, so different models don't share objects #154
 
 v0.9.1 (2018-05-10)
 ...................
diff --git a/pydantic/main.py b/pydantic/main.py
index 94a1020..e9b57a0 100644
--- a/pydantic/main.py
+++ b/pydantic/main.py
@@ -137,6 +137,9 @@ class MetaModel(ABCMeta):
         return super().__new__(mcs, name, bases, new_namespace)
 
 
+_missing = object()
+
+
 class BaseModel(metaclass=MetaModel):
     # populated by the metaclass, defined here to help IDEs only
     __fields__ = {}
@@ -261,18 +264,18 @@ class BaseModel(metaclass=MetaModel):
         errors = []
 
         for name, field in self.__fields__.items():
-            value = input_data.get(field.alias, ...)
-            if value is ... and self.__config__.allow_population_by_alias and field.alt_alias:
-                value = input_data.get(field.name, ...)
+            value = input_data.get(field.alias, _missing)
+            if value is _missing and self.__config__.allow_population_by_alias and field.alt_alias:
+                value = input_data.get(field.name, _missing)
 
-            if value is ...:
+            if value is _missing:
                 if self.__config__.validate_all or field.validate_always:
-                    value = field.default
+                    value = deepcopy(field.default)
                 else:
                     if field.required:
                         errors.append(ErrorWrapper(MissingError(), loc=field.alias, config=self.__config__))
                     else:
-                        values[name] = field.default
+                        values[name] = deepcopy(field.default)
                     continue
 
             v_, errors_ = field.validate(value, values, loc=field.alias, cls=self.__class__)
diff --git a/tests/test_main.py b/tests/test_main.py
index 157e49f..5867912 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Any
+from typing import Any, List
 
 import pytest
 
@@ -452,3 +452,12 @@ def test_set_tuple_values():
     assert m.foo == {'a', 'b'}
     assert m.bar == ('c', 'd')
     assert m.dict() == {'foo': {'a', 'b'}, 'bar': ('c', 'd')}
+
+
+def test_default_copy():
+    class User(BaseModel):
+        friends: List[int] = []
+
+    u1 = User()
+    u2 = User()
+    assert u1.friends is not u2.friends