mypy plugin fixes

Adjustments made to the mypy plugin to accommodate for some potential
changes being made for issue #236 sqlalchemy2-stubs when using SQLAlchemy
1.4. These changes are being kept in sync within SQLAlchemy 2.0.
The changes are also backwards compatible with older versions of
sqlalchemy2-stubs.

Fixed crash in mypy plugin which could occur on both 1.4 and 2.0 versions
if a decorator for the :func:`_orm.registry.mapped` decorator were used
that was referenced in an expression with more than two components (e.g.
``@Backend.mapper_registry.mapped``). This scenario is now ignored; when
using the plugin, the decorator expression needs to be two components (i.e.
``@reg.mapped``).

References: https://github.com/sqlalchemy/sqlalchemy2-stubs/issues/236
Fixes: #9102
Change-Id: Ieb1bf7bf8184645bcd43253e57f1c267b2640537

1 files changed, 7 insertions, 4 deletions

diff --git a/lib/sqlalchemy/ext/mypy/plugin.py b/lib/sqlalchemy/ext/mypy/plugin.py
index e21f1fcb0..22e528387 100644
--- a/lib/sqlalchemy/ext/mypy/plugin.py
+++ b/lib/sqlalchemy/ext/mypy/plugin.py
@@ -201,10 +201,13 @@ def _fill_in_decorators(ctx: ClassDefContext) -> None:
         else:
             continue
 
-        assert isinstance(target.expr, NameExpr)
-        sym = ctx.api.lookup_qualified(
-            target.expr.name, target, suppress_errors=True
-        )
+        if isinstance(target.expr, NameExpr):
+            sym = ctx.api.lookup_qualified(
+                target.expr.name, target, suppress_errors=True
+            )
+        else:
+            continue
+
         if sym and sym.node:
             sym_type = get_proper_type(sym.type)
             if isinstance(sym_type, Instance):