Enhance "raise" strategy to include "raise_on_sql" option

The "raise_on_sql" option differentiates from "raise" in that
firing a lazy loader is OK as long as it does a simple
get from identity map.   Whereas "raise" is more useful
for the case that objects are to be detached.

As part of this, refactors the strategy initiation logic
a bit so that a LoaderStrategy itself knows what "key" was used
to create it, thus allowing variants of a single strategy
based on what the "lazy" argument is.  To achieve this we
have to also get rid of _get_strategy_by_cls().

Everything here is internal with the one exception of an apparently
undocumented, but not underscored, "strategy_class" key
on relationship().   Though it's not clear what
"strategy_class" accomplishes; at this point the strategy
system is extensible using Property.strategy_for().

Fixes: #3812
Change-Id: I812ad878ea5cf764e15f6f71cb39eee78a645d88

1 files changed, 2 insertions, 3 deletions

diff --git a/test/ext/test_baked.py b/test/ext/test_baked.py
index 4250e363b..2f501eb6c 100644
--- a/test/ext/test_baked.py
+++ b/test/ext/test_baked.py
@@ -576,7 +576,7 @@ class ResultTest(BakedTest):
                 Address(id=4, email_address='ed@lala.com'),
             ]),
             User(id=9,
-                addresses=[Address(id=5)], 
+                addresses=[Address(id=5)],
                 orders=[Order(id=2), Order(id=4)]),
             User(id=10, addresses=[])
         ]
@@ -728,7 +728,6 @@ class LazyLoaderTest(BakedTest):
 
     def test_systemwide_loaders_loadable_via_lazyloader(self):
         from sqlalchemy.orm import configure_mappers
-        from sqlalchemy.orm.strategies import LazyLoader
 
         baked.bake_lazy_loaders()
         try:
@@ -738,7 +737,7 @@ class LazyLoaderTest(BakedTest):
 
             is_(
                 User.addresses.property.
-                _get_strategy_by_cls(LazyLoader).__class__,
+                _get_strategy((('lazy', 'select'), )).__class__,
                 BakedLazyLoader
             )
         finally: