Introduce lambda combinations

As the ORM's combinatoric tests mostly use entities and
table metadata that's defined in fixtures, we can't use
@testing.combinations directly as it takes place at the
module level.   Instead we use lambdas, but to reduce
verbosity we use a code replacement so that the namespace
of the lambda can be provided at runtime rather than
module import time.

Change-Id: Ia63a510f9c1d08b055eef62cf047f1f427f0450c

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/util.py b/lib/sqlalchemy/testing/util.py
index 87c461fd2..dbe6a383d 100644
--- a/lib/sqlalchemy/testing/util.py
+++ b/lib/sqlalchemy/testing/util.py
@@ -261,6 +261,21 @@ def flag_combinations(*combinations):
     )
 
 
+def resolve_lambda(__fn, **kw):
+    """Given a no-arg lambda and a namespace, return a new lambda that
+    has all the values filled in.
+
+    This is used so that we can have module-level fixtures that
+    refer to instance-level variables using lambdas.
+
+    """
+
+    glb = dict(__fn.__globals__)
+    glb.update(kw)
+    new_fn = types.FunctionType(__fn.__code__, glb)
+    return new_fn()
+
+
 def metadata_fixture(ddl="function"):
     """Provide MetaData for a pytest fixture."""