From e57f777c4d5f201e367eed173d02e82a7ddbc59c Mon Sep 17 00:00:00 2001
From: Samuel Colvin <s@muelcolvin.com>
Date: Tue, 17 Mar 2020 20:12:30 +0000
Subject: [PATCH] Support instance methods and class methods with
 @validate_arguments (#1272)

---
 changes/1222-samuelcolvin.md |  1 +
 pydantic/decorator.py        | 15 ++++++++---
 tests/test_decorator.py      | 50 +++++++++++++++++++++++++++++++++---
 3 files changed, 59 insertions(+), 7 deletions(-)
 create mode 100644 changes/1222-samuelcolvin.md

diff --git a/changes/1222-samuelcolvin.md b/changes/1222-samuelcolvin.md
new file mode 100644
index 0000000..896fc1e
--- /dev/null
+++ b/changes/1222-samuelcolvin.md
@@ -0,0 +1 @@
+Support instance methods and class methods with `@validate_arguments`
diff --git a/pydantic/decorator.py b/pydantic/decorator.py
index 94e684f..d99ab1d 100644
--- a/pydantic/decorator.py
+++ b/pydantic/decorator.py
@@ -1,4 +1,4 @@
-from functools import update_wrapper
+from functools import wraps
 from typing import TYPE_CHECKING, Any, Dict, List, Mapping, Tuple, TypeVar, cast, get_type_hints
 
 from . import validator
@@ -19,8 +19,15 @@ def validate_arguments(function: 'Callable') -> 'Callable':
     Decorator to validate the arguments passed to a function.
     """
     vd = ValidatedFunction(function)
-    vd = update_wrapper(vd, function)  # type: ignore
-    return cast('Callable', vd)
+
+    @wraps(function)
+    def wrapper_function(*args: Any, **kwargs: Any) -> Any:
+        return vd.call(*args, **kwargs)
+
+    wrapper_function.vd = vd  # type: ignore
+    wrapper_function.raw_function = vd.raw_function  # type: ignore
+    wrapper_function.model = vd.model  # type: ignore
+    return cast('Callable', wrapper_function)
 
 
 ALT_V_ARGS = 'v__args'
@@ -95,7 +102,7 @@ class ValidatedFunction:
 
         self.create_model(fields, takes_args, takes_kwargs)
 
-    def __call__(self, *args: Any, **kwargs: Any) -> Any:
+    def call(self, *args: Any, **kwargs: Any) -> Any:
         values = self.build_values(args, kwargs)
         m = self.model(**values)
         return self.execute(m)
diff --git a/tests/test_decorator.py b/tests/test_decorator.py
index 33acd4f..4727961 100644
--- a/tests/test_decorator.py
+++ b/tests/test_decorator.py
@@ -63,10 +63,10 @@ def test_wrap():
     assert foo_bar.__name__ == 'foo_bar'
     assert foo_bar.__module__ == 'tests.test_decorator'
     assert foo_bar.__qualname__ == 'test_wrap.<locals>.foo_bar'
-    assert isinstance(foo_bar, ValidatedFunction)
+    assert isinstance(foo_bar.vd, ValidatedFunction)
     assert callable(foo_bar.raw_function)
-    assert foo_bar.arg_mapping == {0: 'a', 1: 'b'}
-    assert foo_bar.positional_only_args == set()
+    assert foo_bar.vd.arg_mapping == {0: 'a', 1: 'b'}
+    assert foo_bar.vd.positional_only_args == set()
     assert issubclass(foo_bar.model, BaseModel)
     assert foo_bar.model.__fields__.keys() == {'a', 'b', 'args', 'kwargs'}
     assert foo_bar.model.__name__ == 'FooBar'
@@ -218,3 +218,47 @@ def test_string_annotation():
         {'loc': ('a', 0), 'msg': 'value is not a valid integer', 'type': 'type_error.integer'},
         {'loc': ('b',), 'msg': 'field required', 'type': 'value_error.missing'},
     ]
+
+
+def test_item_method():
+    class X:
+        def __init__(self, v):
+            self.v = v
+
+        @validate_arguments
+        def foo(self, a: int, b: int):
+            assert self.v == a
+            return f'{a}, {b}'
+
+    x = X(4)
+    assert x.foo(4, 2) == '4, 2'
+    assert x.foo(*[4, 2]) == '4, 2'
+
+    with pytest.raises(ValidationError) as exc_info:
+        x.foo()
+
+    assert exc_info.value.errors() == [
+        {'loc': ('a',), 'msg': 'field required', 'type': 'value_error.missing'},
+        {'loc': ('b',), 'msg': 'field required', 'type': 'value_error.missing'},
+    ]
+
+
+def test_class_method():
+    class X:
+        @classmethod
+        @validate_arguments
+        def foo(cls, a: int, b: int):
+            assert cls == X
+            return f'{a}, {b}'
+
+    x = X()
+    assert x.foo(4, 2) == '4, 2'
+    assert x.foo(*[4, 2]) == '4, 2'
+
+    with pytest.raises(ValidationError) as exc_info:
+        x.foo()
+
+    assert exc_info.value.errors() == [
+        {'loc': ('a',), 'msg': 'field required', 'type': 'value_error.missing'},
+        {'loc': ('b',), 'msg': 'field required', 'type': 'value_error.missing'},
+    ]