Fix/22326 placeholder qualified name

mypy/semanal.py

@@ -5972,6 +5972,8 @@ def bind_name_expr(self, expr: NameExpr, sym: SymbolTableNode) -> None:
         ):
             self.fail(f'"{expr.name}" is a type variable and only valid in type context', expr)
         elif isinstance(sym.node, PlaceholderNode):
+            # Preserve the qualified name for plugin hooks during import cycles.
+            expr.fullname = sym.fullname or ""
             self.process_placeholder(expr.name, "name", expr)
         else:
             expr.kind = sym.kind

test-data/unit/check-custom-plugin.test

@@ -723,6 +723,58 @@ class GenericQuerySet(Generic[T]):
 \[mypy]
 plugins=<ROOT>/test-data/unit/plugins/dyn_class_from_method.py
 
+[case testDynamicClassHookImportedPlaceholderCycle]
+# Regression for https://github.com/python/mypy/issues/22326
+# Adapted from the reproduction published by @ayushin in that issue.
+# flags: --config-file tmp/mypy.ini
+from models import Row
+
+reveal_type(Row.objects.base_value())  # N: Revealed type is "builtins.int"
+reveal_type(Row.objects.child_value())  # N: Revealed type is "builtins.str"
+Row.objects.missing()  # E: "ChildManager" has no attribute "missing"
+
+[file models.py]
+from managers import ChildManager
+
+class Row:
+    objects = ChildManager()
+
+[file managers.py]
+from base_managers import BaseManager, BaseQuerySet
+
+class ChildQuerySet(BaseQuerySet):
+    def child_value(self) -> str:
+        return "child"
+
+_ChildManager = BaseManager.from_queryset(ChildQuerySet)
+
+class ChildManager(_ChildManager):
+    pass
+
+[file base_managers.py]
+from typing import Any, Generic, TypeVar
+from models import Row
+
+T = TypeVar("T")
+
+class QuerySet(Generic[T]):
+    @classmethod
+    def from_queryset(cls, queryset_cls: Any) -> Any: ...
+
+class BaseQuerySet(QuerySet[Row]):
+    def base_value(self) -> int:
+        return 1
+
+_BaseManager = QuerySet.from_queryset(BaseQuerySet)
+
+class BaseManager(_BaseManager):
+    pass
+
+[builtins fixtures/classmethod.pyi]
+[file mypy.ini]
+\\[mypy]
+plugins=<ROOT>/test-data/unit/plugins/dyn_class_from_method.py
+
 [case testBaseClassPluginHookWorksIncremental]
 # flags: --config-file tmp/mypy.ini
 import a

test-data/unit/plugins/dyn_class_from_method.py

@@ -9,6 +9,7 @@
     IndexExpr,
     MemberExpr,
     NameExpr,
+    PlaceholderNode,
     RefExpr,
     SymbolTable,
     SymbolTableNode,
@@ -31,23 +32,34 @@ def get_dynamic_class_hook(
 
 
 def add_info_hook(ctx: DynamicClassDefContext) -> None:
+    # Defer until the imported queryset has been fully analysed.
+    fullname = ctx.api.qualified_name(ctx.name)
+    existing = ctx.api.lookup_fully_qualified_or_none(fullname)
+    if existing is not None and isinstance(existing.node, TypeInfo):
+        return
+    assert isinstance(ctx.call.args[0], RefExpr)
+    queryset_fullname = ctx.call.args[0].fullname
+    symbol = (
+        ctx.api.lookup_fully_qualified_or_none(queryset_fullname)
+        if queryset_fullname
+        else None
+    )
+    if symbol is None or not isinstance(symbol.node, TypeInfo) or not symbol.node.mro:
+        assert not ctx.api.final_iteration
+        if existing is None or not isinstance(existing.node, PlaceholderNode):
+            placeholder = PlaceholderNode(fullname, ctx.call, ctx.call.line, becomes_typeinfo=True)
+            ctx.api.add_symbol_table_node(ctx.name, SymbolTableNode(GDEF, placeholder))
+        ctx.api.defer()
+        return
+    queryset_info = symbol.node
     class_def = ClassDef(ctx.name, Block([]))
-    class_def.fullname = ctx.api.qualified_name(ctx.name)
-
+    class_def.fullname = fullname
     info = TypeInfo(SymbolTable(), class_def, ctx.api.cur_mod_id)
     class_def.info = info
-    assert isinstance(ctx.call.args[0], RefExpr)
-    queryset_type_fullname = ctx.call.args[0].fullname
-    queryset_node = ctx.api.lookup_fully_qualified_or_none(queryset_type_fullname)
-    assert queryset_node is not None
-    queryset_info = queryset_node.node
-    assert isinstance(queryset_info, TypeInfo)
-    obj = ctx.api.named_type("builtins.object")
-    info.mro = [info, queryset_info, obj.type]
+    info.mro = [info, *queryset_info.mro]
     info.bases = [Instance(queryset_info, [])]
     ctx.api.add_symbol_table_node(ctx.name, SymbolTableNode(GDEF, info))
 
-
 def as_manager_hook(ctx: DynamicClassDefContext) -> None:
     class_def = ClassDef(ctx.name, Block([]))
     class_def.fullname = ctx.api.qualified_name(ctx.name)