PyObject callable values (#440)

* Support callable as PyObject field

* Add unittests for PyObject callable values

* Update HISTORY.rst

* PyObject minor fixes after code review (#409)

HISTORY.rst

@@ -8,6 +8,7 @@ v0.23 (unreleased)
 * improve documentation for contributing section, # 441 @pilosus
 * improve README.rst to include essential information about the package, #446 by @pilosus
 * ``IntEnum`` support, #444 by @potykion
+* fix PyObject callable value, #409 by @pilosus
 * fix ``ForwardRef`` collection bug, #450 by @tigerwings
 * Support specialized ``ClassVars``, #455 by @tyrylu
 

pydantic/errors.py

@@ -114,7 +114,7 @@ class PathNotADirectoryError(_PathValueError):
 
 
 class PyObjectError(PydanticTypeError):
-    msg_template = 'ensure this value contains valid import path: {error_message}'
+    msg_template = 'ensure this value contains valid import path or valid callable: {error_message}'
 
 
 class SequenceError(PydanticTypeError):

pydantic/main.py

@@ -31,7 +31,7 @@ from .fields import Field
 from .json import custom_pydantic_encoder, pydantic_encoder
 from .parse import Protocol, load_file, load_str_bytes
 from .schema import model_schema
-from .types import StrBytes
+from .types import PyObject, StrBytes
 from .utils import (
     AnyCallable,
     AnyType,
@@ -180,7 +180,11 @@ class MetaModel(ABCMeta):
                 )
 
         for var_name, value in namespace.items():
-            if not var_name.startswith('_') and not isinstance(value, TYPE_BLACKLIST) and var_name not in class_vars:
+            if (
+                not var_name.startswith('_')
+                and (annotations.get(var_name) == PyObject or not isinstance(value, TYPE_BLACKLIST))
+                and var_name not in class_vars
+            ):
                 validate_field_name(bases, var_name)
                 fields[var_name] = Field.infer(
                     name=var_name,

pydantic/types.py

@@ -12,7 +12,7 @@ from ipaddress import (
     _BaseNetwork,
 )
 from pathlib import Path
-from typing import TYPE_CHECKING, Any, Dict, Generator, Optional, Pattern, Set, Tuple, Type, Union, cast
+from typing import TYPE_CHECKING, Any, Callable, Dict, Generator, Optional, Pattern, Set, Tuple, Type, Union, cast
 from uuid import UUID
 
 from . import errors
@@ -268,11 +268,18 @@ class PyObject:
 
     @classmethod
     def __get_validators__(cls) -> 'CallableGenerator':
-        yield str_validator
         yield cls.validate
 
     @classmethod
     def validate(cls, value: Any) -> Any:
+        if isinstance(value, Callable):  # type: ignore
+            return value
+
+        try:
+            value = str_validator(value)
+        except errors.StrError:
+            raise errors.PyObjectError(error_message='value is neither a valid import path not a valid callable')
+
         if value is not None:
             try:
                 return import_string(value)

tests/test_types.py

@@ -48,6 +48,10 @@ class ConBytesModel(BaseModel):
     v: conbytes(max_length=10) = b'foobar'
 
 
+def foo():
+    return 42
+
+
 def test_constrained_bytes_good():
     m = ConBytesModel(v=b'short')
     assert m.v == b'short'
@@ -145,7 +149,8 @@ def test_module_import():
     assert exc_info.value.errors() == [
         {
             'loc': ('module',),
-            'msg': 'ensure this value contains valid import path: ' '"foobar" doesn\'t look like a module path',
+            'msg': 'ensure this value contains valid import path or valid callable: '
+            '"foobar" doesn\'t look like a module path',
             'type': 'type_error.pyobject',
             'ctx': {'error_message': '"foobar" doesn\'t look like a module path'},
         }
@@ -156,12 +161,25 @@ def test_module_import():
     assert exc_info.value.errors() == [
         {
             'loc': ('module',),
-            'msg': 'ensure this value contains valid import path: ' 'Module "os" does not define a "missing" attribute',
+            'msg': 'ensure this value contains valid import path or valid callable: '
+            'Module "os" does not define a "missing" attribute',
             'type': 'type_error.pyobject',
             'ctx': {'error_message': 'Module "os" does not define a "missing" attribute'},
         }
     ]
 
+    with pytest.raises(ValidationError) as exc_info:
+        PyObjectModel(module=[1, 2, 3])
+    assert exc_info.value.errors() == [
+        {
+            'loc': ('module',),
+            'msg': 'ensure this value contains valid import path or valid callable: '
+            'value is neither a valid import path not a valid callable',
+            'type': 'type_error.pyobject',
+            'ctx': {'error_message': 'value is neither a valid import path not a valid callable'},
+        }
+    ]
+
 
 def test_pyobject_none():
     class PyObjectModel(BaseModel):
@@ -171,6 +189,15 @@ def test_pyobject_none():
     assert m.module is None
 
 
+def test_pyobject_callable():
+    class PyObjectModel(BaseModel):
+        foo: PyObject = foo
+
+    m = PyObjectModel()
+    assert m.foo is foo
+    assert m.foo() == 42
+
+
 class CheckModel(BaseModel):
     bool_check = True
     str_check = 's'