Major fixes and new features

venv/lib/python3.12/site-packages/mypy/lookup.py

@@ -0,0 +1,61 @@
+"""
+This is a module for various lookup functions:
+functions that will find a semantic node by its name.
+"""
+
+from __future__ import annotations
+
+from mypy.nodes import MypyFile, SymbolTableNode, TypeInfo
+
+# TODO: gradually move existing lookup functions to this module.
+
+
+def lookup_fully_qualified(
+    name: str, modules: dict[str, MypyFile], *, raise_on_missing: bool = False
+) -> SymbolTableNode | None:
+    """Find a symbol using it fully qualified name.
+
+    The algorithm has two steps: first we try splitting the name on '.' to find
+    the module, then iteratively look for each next chunk after a '.' (e.g. for
+    nested classes).
+
+    This function should *not* be used to find a module. Those should be looked
+    in the modules dictionary.
+    """
+    head = name
+    rest = []
+    # 1. Find a module tree in modules dictionary.
+    while True:
+        if "." not in head:
+            if raise_on_missing:
+                assert "." in head, f"Cannot find module for {name}"
+            return None
+        head, tail = head.rsplit(".", maxsplit=1)
+        rest.append(tail)
+        mod = modules.get(head)
+        if mod is not None:
+            break
+    names = mod.names
+    # 2. Find the symbol in the module tree.
+    if not rest:
+        # Looks like a module, don't use this to avoid confusions.
+        if raise_on_missing:
+            assert rest, f"Cannot find {name}, got a module symbol"
+        return None
+    while True:
+        key = rest.pop()
+        if key not in names:
+            if raise_on_missing:
+                assert key in names, f"Cannot find component {key!r} for {name!r}"
+            return None
+        stnode = names[key]
+        if not rest:
+            return stnode
+        node = stnode.node
+        # In fine-grained mode, could be a cross-reference to a deleted module
+        # or a Var made up for a missing module.
+        if not isinstance(node, TypeInfo):
+            if raise_on_missing:
+                assert node, f"Cannot find {name}"
+            return None
+        names = node.names