Allow a function for view_config(context) (useful with venusian lift)

CHANGES.rst

@@ -11,8 +11,9 @@ Features
 
 - Coverage reports in tests based on Python 3.11 instead of Python 3.8.
 
-- Added `Self` sentinel value that may be used for context and name arguments
-  to view_config on class methods in conjunction with venusian lift.
+- Added `Self` sentinel value that may be used for context and name or
+  function as context arguments to view_config on class methods in conjunction
+  with venusian lift.
 
 Bug Fixes
 ---------

src/pyramid/config/views.py

@@ -591,7 +591,9 @@ def wrapper(context, request):
           exceptions, then set the ``exception_only`` to ``True``.
           When :term:`view` is a class, the sentinel value view.Self
           will cause the :term:`context` value to be set at scan time
-          (useful in conjunction with venusian lift).
+          (useful in conjunction with venusian lift). It can also be
+          a function taking the view as it's only argument which return
+          value will be set as context at scan time.
 
         route_name
 
@@ -823,10 +825,15 @@ def wrapper(context, request):
         if inspect.isclass(view):
             if context is Self:
                 context = view
+            elif inspect.isfunction(context):
+                context = context(view)
             if name is Self:
                 name = attr or ""
         elif Self in (context, name):
             raise ValueError('Self is only allowed when view is a class')
+        elif inspect.isfunction(context):
+            raise ValueError(
+                'context as function is only allowed when view is a class')
 
         if is_nonstr_iter(decorator):
             decorator = combine_decorators(*map(self.maybe_dotted, decorator))

tests/test_config/test_views.py

@@ -446,6 +446,16 @@ def view(exc, request):  # pragma: no cover
             lambda: config.add_view(view=view, context=Self, name=Self),
         )
 
+    def test_add_view_raises_on_function_context_with_non_class_view(self):
+        def view(exc, request):  # pragma: no cover
+            pass
+
+        config = self._makeOne(autocommit=True)
+        self.assertRaises(
+            ValueError,
+            lambda: config.add_view(view=view, context=lambda x: x, name=Self),
+        )
+
     def test_add_view_replaces_self(self):
         from zope.interface import implementedBy
 
@@ -462,6 +472,26 @@ def view(self):
         wrapper = self._getViewCallable(config, interface, name='view')
         self.assertEqual(wrapper.__original_view__, Foo)
 
+    def test_add_view_replaces_function(self):
+        from zope.interface import implementedBy
+
+        class Foo2:
+            pass
+
+        class Foo:  # pragma: no cover
+            wrapped = Foo2
+            def __init__(self, request):
+                pass
+
+            def view(self):
+                pass
+
+        config = self._makeOne(autocommit=True)
+        config.add_view(Foo, context=lambda x: x.wrapped, name=Self, attr='view')
+        interface = implementedBy(Foo2)
+        wrapper = self._getViewCallable(config, interface, name='view')
+        self.assertEqual(wrapper.__original_view__, Foo)
+
     def test_add_view_context_as_iface(self):
         from pyramid.renderers import null_renderer