Add scalars method to connection and session classes

Added new methods :meth:`_orm.Session.scalars`,
:meth:`_engine.Connection.scalars`, :meth:`_asyncio.AsyncSession.scalars`
and :meth:`_asyncio.AsyncSession.stream_scalars`, which provide a short cut
to the use case of receiving a row-oriented :class:`_result.Result` object
and converting it to a :class:`_result.ScalarResult` object via the
:meth:`_engine.Result.scalars` method, to return a list of values rather
than a list of rows. The new methods are analogous to the long existing
:meth:`_orm.Session.scalar` and :meth:`_engine.Connection.scalar` methods
used to return a single value from the first row only. Pull request
courtesy Miguel Grinberg.

Fixes: #6990
Closes: #6991
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/6991
Pull-request-sha: b3e0bb3042c55b0cc5af6a25cb3f31b929f88a47

Change-Id: Ia445775e24ca964b0162c2c8e5ca67dd1e39199f

1 files changed, 19 insertions, 0 deletions

diff --git a/test/ext/asyncio/test_session_py3k.py b/test/ext/asyncio/test_session_py3k.py
index cd9054740..4e475b212 100644
--- a/test/ext/asyncio/test_session_py3k.py
+++ b/test/ext/asyncio/test_session_py3k.py
@@ -91,6 +91,25 @@ class AsyncSessionQueryTest(AsyncFixture):
         result = await async_session.scalar(stmt)
         eq_(result, 7)
 
+    @testing.combinations(
+        ("scalars",), ("stream_scalars",), argnames="filter_"
+    )
+    @async_test
+    async def test_scalars(self, async_session, filter_):
+        User = self.classes.User
+
+        stmt = (
+            select(User)
+            .options(selectinload(User.addresses))
+            .order_by(User.id)
+        )
+
+        if filter_ == "scalars":
+            result = (await async_session.scalars(stmt)).all()
+        elif filter_ == "stream_scalars":
+            result = await (await async_session.stream_scalars(stmt)).all()
+        eq_(result, self.static.user_address_result)
+
     @async_test
     async def test_get(self, async_session):
         User = self.classes.User