Consider usefixtures marker for enforcing params

Author: nicoddemus

src/_pytest/fixtures.py

@@ -1272,10 +1272,8 @@ def getfixtureinfo(self, node, func, cls, funcargs=True):
         else:
             argnames = ()
 
-        usefixtures = itertools.chain.from_iterable(
-            mark.args for mark in node.iter_markers(name="usefixtures")
-        )
-        initialnames = tuple(usefixtures) + argnames
+        usefixtures = get_use_fixtures_for_node(node)
+        initialnames = usefixtures + argnames
         fm = node.session._fixturemanager
         initialnames, names_closure, arg2fixturedefs = fm.getfixtureclosure(
             initialnames, node, ignore_args=self._get_direct_parametrize_args(node)
@@ -1472,3 +1470,13 @@ def _matchfactories(self, fixturedefs, nodeid):
         for fixturedef in fixturedefs:
             if nodes.ischildnode(fixturedef.baseid, nodeid):
                 yield fixturedef
+
+
+def get_use_fixtures_for_node(node) -> Tuple[str, ...]:
+    """Returns the names of all the usefixtures() marks on the given node"""
+    return tuple(
+        str(x)
+        for x in itertools.chain.from_iterable(
+            mark.args for mark in node.iter_markers(name="usefixtures")
+        )
+    )

src/_pytest/python.py

@@ -1162,7 +1162,6 @@ def _validate_explicit_parameters(self, argnames, indirect):
         :param indirect: same ``indirect`` parameter of ``parametrize()``.
         :raise ValueError: if validation fails
         """
-        func_name = self.function.__name__
         if isinstance(indirect, bool) and indirect is True:
             return
         parametrized_argnames = list()
@@ -1173,13 +1172,17 @@ def _validate_explicit_parameters(self, argnames, indirect):
                     parametrized_argnames.append(arg)
         elif indirect is False:
             parametrized_argnames = argnames
+
+        usefixtures = fixtures.get_use_fixtures_for_node(self.definition)
+
         for arg in parametrized_argnames:
-            if arg not in funcargnames:
-                raise ValueError(
-                    f'In function "{func_name}":\n'
-                    f'Parameter "{arg}" should be declared explicitly via indirect\n'
-                    f"or in function itself"
-                )
+            if arg not in funcargnames and arg not in usefixtures:
+                func_name = self.function.__name__
+                msg = (
+                    'In function "{func_name}":\n'
+                    'Parameter "{arg}" should be declared explicitly via indirect or in function itself'
+                ).format(func_name=func_name, arg=arg)
+                fail(msg, pytrace=False)
 
 
 def _find_parametrized_scope(argnames, arg2fixturedefs, indirect):

testing/python/metafunc.py

@@ -28,6 +28,9 @@ def __init__(self, names):
         class DefinitionMock(python.FunctionDefinition):
             obj = attr.ib()
 
+            def listchain(self):
+                return []
+
         names = fixtures.getfuncargnames(func)
         fixtureinfo = FixtureInfo(names)
         definition = DefinitionMock._create(func)