Merge pull request #166 from Point72/vs/null_context

Make NullContext an alias of ContextBase

Author: feussy

ccflow/base.py

@@ -829,6 +829,9 @@ class ContextBase(ResultBase):
 
     @model_validator(mode="wrap")
     def _context_validator(cls, v, handler, info):
+        if v is None:
+            return handler({})
+
         # Add deepcopy for v2 because it doesn't support copy_on_model_validation
         v = copy.deepcopy(v)
 

ccflow/context.py

@@ -90,15 +90,8 @@
 
 _SEPARATOR = ","
 
-
-class NullContext(ContextBase):
-    """A Null Context that is used when no context is provided."""
-
-    @model_validator(mode="wrap")
-    def _validate_none(cls, v, handler, info):
-        v = v or {}
-        return handler(v)
-
+# Starting 0.8.0 Nullcontext is an alias to ContextBase
+NullContext = ContextBase
 
 C = TypeVar("C", bound=Hashable)
 

ccflow/tests/test_callable.py

@@ -32,6 +32,10 @@ class MyExtendedContext(MyContext):
     c: bool
 
 
+class MyOtherContext(ContextBase):
+    a: int
+
+
 class ListContext(ContextBase):
     ll: List[str] = []
 
@@ -152,7 +156,7 @@ class BadModelMismatchedContextAndCall(CallableModel):
 
     @property
     def context_type(self):
-        return NullContext
+        return MyOtherContext
 
     @property
     def result_type(self):
@@ -163,7 +167,7 @@ def __call__(self, context: MyContext) -> MyResult:
         return context
 
 
-class BadModelGenericMismatchedContextAndCall(CallableModelGenericType[NullContext, MyResult]):
+class BadModelGenericMismatchedContextAndCall(CallableModelGenericType[MyOtherContext, MyResult]):
     """Model with mismatched context_type and __call__ annotation"""
 
     @Flow.call
@@ -460,7 +464,7 @@ def test_types(self):
         error = "__call__ method must take a single argument, named 'context'"
         self.assertRaisesRegex(ValueError, error, BadModelDoubleContextArg)
 
-        error = "The context_type <class 'ccflow.context.NullContext'> must match the type of the context accepted by __call__ <class 'ccflow.tests.test_callable.MyContext'>"
+        error = "The context_type <class 'ccflow.tests.test_callable.MyOtherContext'> must match the type of the context accepted by __call__ <class 'ccflow.tests.test_callable.MyContext'>"
         self.assertRaisesRegex(ValueError, error, BadModelMismatchedContextAndCall)
 
         error = "The result_type <class 'ccflow.result.generic.GenericResult'> must match the return type of __call__ <class 'ccflow.tests.test_callable.MyResult'>"
@@ -642,7 +646,7 @@ def __call__(self, context: NullContext) -> GenericResult[float]:
             MyCallable()
 
     def test_types_generic(self):
-        error = "Context type annotation <class 'ccflow.tests.test_callable.MyContext'> on __call__ does not match context_type <class 'ccflow.context.NullContext'> defined by CallableModelGenericType"
+        error = "Context type annotation <class 'ccflow.tests.test_callable.MyContext'> on __call__ does not match context_type <class 'ccflow.tests.test_callable.MyOtherContext'> defined by CallableModelGenericType"
         self.assertRaisesRegex(TypeError, error, BadModelGenericMismatchedContextAndCall)
 
         error = "Return type annotation <class 'ccflow.tests.test_callable.MyResult'> on __call__ does not match result_type <class 'ccflow.result.generic.GenericResult'> defined by CallableModelGenericType"

ccflow/tests/test_context.py

@@ -30,6 +30,11 @@
 from ccflow.result import GenericResult
 
 
+class MyDefaultContext(ContextBase):
+    b: float = 3.14
+    c: bool = False
+
+
 class TestContexts(TestCase):
     def test_null_context(self):
         n1 = NullContext()
@@ -38,11 +43,25 @@ def test_null_context(self):
         self.assertEqual(hash(n1), hash(n2))
 
     def test_null_context_validation(self):
+        # Context creation is based on two main assumptions:
+        # 1. If there is enough information to create a context, it should be created.
+        # 2. Since NullContext has no required fields, it can be created from None,
+        #    empty containers ({} or []), or any other context.
         self.assertEqual(NullContext.model_validate([]), NullContext())
         self.assertEqual(NullContext.model_validate({}), NullContext())
         self.assertEqual(NullContext.model_validate(None), NullContext())
+        self.assertIsInstance(NullContext.model_validate(DateContext(date="0d")), NullContext)
         self.assertRaises(ValueError, NullContext.model_validate, [True])
 
+    def test_context_with_defaults(self):
+        # Contexts may define default values. Extending the assumptions above:
+        # Any context inherits the behavior from NullContext, and can be
+        # created as long as all required fields (if any) are satisfied.
+        self.assertEqual(TypeAdapter(MyDefaultContext).validate_python(None), MyDefaultContext(b=3.14, c=False))
+        self.assertEqual(TypeAdapter(MyDefaultContext).validate_python({}), MyDefaultContext(b=3.14, c=False))
+        self.assertEqual(TypeAdapter(MyDefaultContext).validate_python([]), MyDefaultContext(b=3.14, c=False))
+        self.assertEqual(TypeAdapter(MyDefaultContext).validate_python({"b": 10.0}), MyDefaultContext(b=10.0, c=False))
+
     def test_date_validation(self):
         c = DateContext(date=date.today())
         self.assertEqual(DateContext(date=str(date.today())), c)
@@ -228,8 +247,6 @@ def setUp(self):
             for name, obj in inspect.getmembers(ctx, inspect.isclass)
             if obj.__module__ == ctx.__name__ and issubclass(obj, ContextBase) and not getattr(obj, "__deprecated__", False)
         }
-        # TODO - remove NullContext until we fix the inheritance
-        self.classes.pop("NullContext")
 
     def test_field_ordering(self):
         """Test that complex contexts have fields in the same order as the basic contexts they are composed of."""