WIP: more detailed ctor handling

Author: RonnyPfannschmidt

src/_pytest/nodes.py

@@ -115,30 +115,57 @@ class Node(metaclass=NodeMeta):
         "__dict__",
     )
 
+    name: str
+    parent: Optional["Node"]
+    config: Config
+    session: "Session"
+    fs_path: Path
+    _nodeid: str
+
     def __init__(
         self,
         *,
         name: str,
         parent: Optional["Node"],
-        config: Config,
-        session: "Session",
-        fs_path: Path,
-        nodeid: str,
+        config: Optional[Config],
+        session: Optional["Session"],
+        fs_path: Optional[Path],
+        nodeid: Optional[str],
     ) -> None:
         #: A unique name within the scope of the parent node.
         self.name = name
+
+        if nodeid is not None:
+            assert "::()" not in nodeid
+        else:
+            assert parent is not None
+            nodeid = parent.nodeid
+            if name != "()":
+                nodeid = f"{nodeid}::{name}"
         self._nodeid = nodeid
         #: The parent collector node.
         self.parent = parent
 
         #: The pytest config object.
-        self.config = config
+        if config is None:
+            assert parent is not None
+            self.config = parent.config
+        else:
+            self.config = config
 
         #: The pytest session this node is part of.
-        self.session = session
+        if session is None:
+            assert parent is not None
+            self.session = parent.session
+        else:
+            self.session = session
 
         #: Filesystem path where this node was collected from (can be None).
-        self.fs_path = fs_path
+        if fs_path is None:
+            assert parent is not None
+            self.fs_path = parent.fs_path
+        else:
+            self.fs_path = fs_path
 
         #: Keywords/markers collected from all scopes.
         self.keywords = NodeKeywords(self)
@@ -509,6 +536,17 @@ def _check_initialpaths_for_relpath(
 
 
 class FSCollector(Collector):
+    def __init__(self, **kw):
+
+        fs_path: Optional[Path] = kw.pop("fs_path", None)
+        fspath: Optional[py.path.local] = kw.pop("fspath", None)
+
+        if fspath is not None:
+            assert fs_path is None
+            fs_path = Path(fspath)
+        kw["fs_path"] = fs_path
+        super().__init__(**kw)
+
     @classmethod
     def from_parent(
         cls,