typing adjustments for composites

* if dataclass isn't used, columns have to be named
* _CompositeClassProto is not useful as dataclasses have no
  methods / bases we can use, so composite is against Any
* Adjust session.get() feature to work w/ dataclass composites

Change-Id: Icc606cc76871c738dc794ea4555fca8a1ab0e0fd

1 files changed, 51 insertions, 0 deletions

diff --git a/test/ext/mypy/plain_files/composite_dc.py b/test/ext/mypy/plain_files/composite_dc.py
new file mode 100644
index 000000000..fa1b16a2a
--- /dev/null
+++ b/test/ext/mypy/plain_files/composite_dc.py
@@ -0,0 +1,51 @@
+import dataclasses
+
+from sqlalchemy import select
+from sqlalchemy.orm import composite
+from sqlalchemy.orm import DeclarativeBase
+from sqlalchemy.orm import Mapped
+from sqlalchemy.orm import mapped_column
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+@dataclasses.dataclass
+class Point:
+    def __init__(self, x: int, y: int):
+        self.x = x
+        self.y = y
+
+
+class Vertex(Base):
+    __tablename__ = "vertices"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    x1: Mapped[int]
+    y1: Mapped[int]
+    x2: Mapped[int]
+    y2: Mapped[int]
+
+    # inferred from right hand side
+    start = composite(Point, "x1", "y1")
+
+    # taken from left hand side
+    end: Mapped[Point] = composite(Point, "x2", "y2")
+
+
+v1 = Vertex(start=Point(3, 4), end=Point(5, 6))
+
+stmt = select(Vertex).where(Vertex.start.in_([Point(3, 4)]))
+
+# EXPECTED_TYPE: Select[Tuple[Vertex]]
+reveal_type(stmt)
+
+# EXPECTED_TYPE: composite.Point
+reveal_type(v1.start)
+
+# EXPECTED_TYPE: composite.Point
+reveal_type(v1.end)
+
+# EXPECTED_TYPE: int
+reveal_type(v1.end.y)