From b87e2492ccb7811cb07b8fe62c7ec42fc7cc35ce Mon Sep 17 00:00:00 2001
From: Samuel Colvin <s@muelcolvin.com>
Date: Sat, 13 Feb 2021 15:48:55 +0000
Subject: [PATCH] ensure cythonized functions are left untouched2 (#2228)

* ensure cythonized functions are left untouched2

* add change
---
 changes/2228-samuelcolvin.md |  1 +
 pydantic/main.py             |  9 +++++++--
 setup.cfg                    |  1 +
 tests/test_edge_cases.py     | 28 ++++++++++++++++++++++++++++
 4 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 changes/2228-samuelcolvin.md

diff --git a/changes/2228-samuelcolvin.md b/changes/2228-samuelcolvin.md
new file mode 100644
index 0000000..05d4606
--- /dev/null
+++ b/changes/2228-samuelcolvin.md
@@ -0,0 +1 @@
+ensure cythonized functions are left untouched when creating models, based on #1944 by @kollmats
diff --git a/pydantic/main.py b/pydantic/main.py
index c00cd1f..75ae920 100644
--- a/pydantic/main.py
+++ b/pydantic/main.py
@@ -259,6 +259,11 @@ class ModelMetaclass(ABCMeta):
 
         prepare_config(config, name)
 
+        untouched_types = ANNOTATED_FIELD_UNTOUCHED_TYPES
+
+        def is_untouched(v: Any) -> bool:
+            return isinstance(v, untouched_types) or v.__class__.__name__ == 'cython_function_or_method'
+
         if (namespace.get('__module__'), namespace.get('__qualname__')) != ('pydantic.main', 'BaseModel'):
             annotations = resolve_annotations(namespace.get('__annotations__', {}), namespace.get('__module__', None))
             # annotation only fields need to come first in fields
@@ -270,7 +275,7 @@ class ModelMetaclass(ABCMeta):
                     value = namespace.get(ann_name, Undefined)
                     allowed_types = get_args(ann_type) if get_origin(ann_type) is Union else (ann_type,)
                     if (
-                        isinstance(value, ANNOTATED_FIELD_UNTOUCHED_TYPES)
+                        is_untouched(value)
                         and ann_type != PyObject
                         and not any(
                             lenient_issubclass(get_origin(allowed_type), Type) for allowed_type in allowed_types
@@ -289,7 +294,7 @@ class ModelMetaclass(ABCMeta):
 
             untouched_types = UNTOUCHED_TYPES + config.keep_untouched
             for var_name, value in namespace.items():
-                can_be_changed = var_name not in class_vars and not isinstance(value, untouched_types)
+                can_be_changed = var_name not in class_vars and not is_untouched(value)
                 if isinstance(value, ModelPrivateAttr):
                     if not is_valid_private_name(var_name):
                         raise NameError(
diff --git a/setup.cfg b/setup.cfg
index 0154d92..93865e1 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -4,6 +4,7 @@ addopts = -p no:hypothesispytest
 filterwarnings =
     error
     ignore::DeprecationWarning:distutils
+    ignore::DeprecationWarning:Cython
 
 [flake8]
 max-line-length = 120
diff --git a/tests/test_edge_cases.py b/tests/test_edge_cases.py
index 04d34aa..5ad7347 100644
--- a/tests/test_edge_cases.py
+++ b/tests/test_edge_cases.py
@@ -20,6 +20,11 @@ from pydantic import (
 )
 from pydantic.fields import Field, Schema
 
+try:
+    import cython
+except ImportError:
+    cython = None
+
 
 def test_str_bytes():
     class Model(BaseModel):
@@ -1745,3 +1750,26 @@ def test_default_factory_validator_child():
         pass
 
     assert Child(foo=['a', 'b']).foo == ['a-1', 'b-1']
+
+
+@pytest.mark.skipif(cython is None, reason='cython not installed')
+def test_cython_function_untouched():
+    Model = cython.inline(
+        # language=Python
+        """
+from pydantic import BaseModel
+
+class Model(BaseModel):
+    a = 0.0
+    b = 10
+
+    def get_double_a(self) -> float:
+        return self.a + self.b
+
+return Model
+"""
+    )
+    model = Model(a=10.2)
+    assert model.a == 10.2
+    assert model.b == 10
+    return model.get_double_a() == 20.2