WIP POC RFC: remove config/session as possible parameters for node

src/_pytest/main.py

@@ -374,9 +374,11 @@ class Session(nodes.FSCollector):
     _setupstate = None  # type: SetupState
 
     def __init__(self, config):
-        nodes.FSCollector.__init__(
-            self, config.rootdir, parent=None, config=config, session=self, nodeid=""
-        )
+        self.config = config
+        self.fspath = config.rootdir
+        self.session = self
+        super().__init__(fspath=config.rootdir, parent=self, nodeid="")
+        self.parent = None
         self.testsfailed = 0
         self.testscollected = 0
         self.shouldstop = False

src/_pytest/nodes.py

@@ -2,6 +2,7 @@
 import warnings
 from functools import lru_cache
 from typing import Any
+from typing import cast
 from typing import Dict
 from typing import List
 from typing import Optional
@@ -17,7 +18,6 @@
 from _pytest._code.code import ReprExceptionInfo
 from _pytest.compat import cached_property
 from _pytest.compat import getfslineno
-from _pytest.config import Config
 from _pytest.deprecated import NODE_USE_FROM_PARENT
 from _pytest.fixtures import FixtureDef
 from _pytest.fixtures import FixtureLookupError
@@ -30,6 +30,7 @@
 if False:  # TYPE_CHECKING
     # Imported here due to circular import.
     from _pytest.main import Session  # noqa: F401
+    from _pytest.config import Config  # noqa: F401
 
 SEP = "/"
 
@@ -90,37 +91,27 @@ class Node(metaclass=NodeMeta):
     def __init__(
         self,
         name,
-        parent: Optional["Node"] = None,
-        config: Optional[Config] = None,
-        session: Optional["Session"] = None,
+        parent: Union["Node", "Session"],
         fspath: Optional[py.path.local] = None,
         nodeid: Optional[str] = None,
     ) -> None:
         #: a unique name within the scope of the parent node
         self.name = name
 
         #: the parent collector node.
-        self.parent = parent
-
-        #: the pytest config object
-        if config:
-            self.config = config
+        if parent is self:
+            self.parent: Optional["Node"] = None  # temporary hack for session
+            self.session = cast("Session", parent)
         else:
-            if not parent:
-                raise TypeError("config or parent must be provided")
-            self.config = parent.config
-
-        #: the session this node is part of
-        if session:
-            self.session = session
-        else:
-            if not parent:
-                raise TypeError("session or parent must be provided")
+            self.parent = parent
+            #: the session this node is part of
             self.session = parent.session
 
-        #: filesystem path where this node was collected from (can be None)
-        self.fspath = fspath or getattr(parent, "fspath", None)
+        #: the pytest config object
+        self.config: "Config" = parent.config
 
+        #: filesystem path where this node was collected from (can be None)
+        self.fspath: py.path.local = fspath or parent.fspath
         #: keywords/markers collected from all scopes
         self.keywords = NodeKeywords(self)
 
@@ -409,9 +400,7 @@ def _check_initialpaths_for_relpath(session, fspath):
 
 
 class FSCollector(Collector):
-    def __init__(
-        self, fspath: py.path.local, parent=None, config=None, session=None, nodeid=None
-    ) -> None:
+    def __init__(self, fspath: py.path.local, parent, nodeid=None) -> None:
         name = fspath.basename
         if parent is not None:
             rel = fspath.relto(parent.fspath)
@@ -420,7 +409,7 @@ def __init__(
             name = name.replace(os.sep, SEP)
         self.fspath = fspath
 
-        session = session or parent.session
+        session = parent.session
 
         if nodeid is None:
             nodeid = self.fspath.relto(session.config.rootdir)
@@ -430,7 +419,7 @@ def __init__(
             if nodeid and os.sep != SEP:
                 nodeid = nodeid.replace(os.sep, SEP)
 
-        super().__init__(name, parent, config, session, nodeid=nodeid, fspath=fspath)
+        super().__init__(name=name, parent=parent, nodeid=nodeid, fspath=fspath)
 
     @classmethod
     def from_parent(cls, parent, *, fspath):
@@ -448,8 +437,8 @@ class Item(Node):
 
     nextitem = None
 
-    def __init__(self, name, parent=None, config=None, session=None, nodeid=None):
-        super().__init__(name, parent, config, session, nodeid=nodeid)
+    def __init__(self, name, parent=None, nodeid=None):
+        super().__init__(name=name, parent=parent, nodeid=nodeid)
         self._report_sections = []  # type: List[Tuple[str, str, str]]
 
         #: user properties is a list of tuples (name, value) that holds user

src/_pytest/python.py

@@ -539,11 +539,9 @@ def _importtestmodule(self):
 
 
 class Package(Module):
-    def __init__(self, fspath, parent=None, config=None, session=None, nodeid=None):
+    def __init__(self, fspath, parent=None, nodeid=None):
         session = parent.session
-        nodes.FSCollector.__init__(
-            self, fspath, parent=parent, config=config, session=session, nodeid=nodeid
-        )
+        nodes.FSCollector.__init__(self, fspath, parent=parent, nodeid=nodeid)
         self.name = fspath.dirname
         self.trace = session.trace
         self._norecursepatterns = session._norecursepatterns
@@ -1405,15 +1403,13 @@ def __init__(
         name,
         parent,
         args=None,
-        config=None,
         callspec=None,
         callobj=NOTSET,
         keywords=None,
-        session=None,
         fixtureinfo=None,
         originalname=None,
     ):
-        super().__init__(name, parent, config=config, session=session)
+        super().__init__(name=name, parent=parent)
         self._args = args
         if callobj is not NOTSET:
             self.obj = callobj

testing/deprecated_test.py

@@ -79,14 +79,26 @@ def test_foo():
 
 
 def test_node_direct_ctor_warning():
-    class MockConfig:
-        pass
+    class MockAll:
+        @property
+        def parent(self):
+            return None
+
+        @property
+        def config(self):
+            return self
+
+        @property
+        def session(self):
+            return self
+
+        fspath = None
 
-    ms = MockConfig()
+    ms = MockAll()
     with pytest.warns(
         DeprecationWarning,
         match="direct construction of .* has been deprecated, please use .*.from_parent",
     ) as w:
-        nodes.Node(name="test", config=ms, session=ms, nodeid="None")
+        nodes.Node(name="test", parent=ms, nodeid="None")
     assert w[0].lineno == inspect.currentframe().f_lineno - 1
     assert w[0].filename == __file__

testing/example_scripts/fixtures/custom_item/conftest.py

@@ -1,10 +1,10 @@
 import pytest
 
 
-class CustomItem(pytest.Item, pytest.File):
+class CustomItem(pytest.Item):
     def runtest(self):
         pass
 
 
 def pytest_collect_file(path, parent):
-    return CustomItem(path, parent)
+    return CustomItem.from_parent(parent, fspath=path)

testing/python/collect.py

@@ -284,7 +284,7 @@ def make_function(testdir, **kwargs):
         session = testdir.Session.from_config(config)
         session._fixturemanager = FixtureManager(session)
 
-        return pytest.Function.from_parent(config=config, parent=session, **kwargs)
+        return pytest.Function.from_parent(parent=session, **kwargs)
 
     def test_function_equality(self, testdir, tmpdir):
         def func1():

testing/python/fixtures.py

@@ -1534,6 +1534,7 @@ def test_package(one):
         reprec = testdir.inline_run()
         reprec.assertoutcome(passed=2)
 
+    @pytest.mark.xfail(reason="file item dulity mess")
     def test_collect_custom_items(self, testdir):
         testdir.copy_example("fixtures/custom_item")
         result = testdir.runpytest("foo")

testing/test_collection.py

@@ -746,6 +746,7 @@ def test_y(self):
         assert ids == ["MyTestSuite.x_test", "TestCase.test_y"]
 
 
+@pytest.mark.xfail(reason="item<>file missmatch, a mess we should break")
 def test_matchnodes_two_collections_same_file(testdir):
     testdir.makeconftest(
         """
@@ -756,18 +757,18 @@ def pytest_configure(config):
         class Plugin2(object):
             def pytest_collect_file(self, path, parent):
                 if path.ext == ".abc":
-                    return MyFile2(path, parent)
+                    return MyFile2.from_parent(parent, fspath=path)
 
         def pytest_collect_file(path, parent):
             if path.ext == ".abc":
-                return MyFile1(path, parent)
+                return MyFile1.from_parent(parent, fspath=path)
 
-        class MyFile1(pytest.Item, pytest.File):
+        class MyFile1(pytest.Item):
             def runtest(self):
                 pass
         class MyFile2(pytest.File):
             def collect(self):
-                return [Item2("hello", parent=self)]
+                return [Item2.from_parent(name="hello", parent=self)]
 
         class Item2(pytest.Item):
             def runtest(self):