- [feature] Added a new system

for registration of new dialects in-process
without using an entrypoint.  See the
docs for "Registering New Dialects".
[ticket:2462]

2 files changed, 40 insertions, 1 deletions

diff --git a/lib/sqlalchemy/util/__init__.py b/lib/sqlalchemy/util/__init__.py
index 13914aa7d..76c3c829d 100644
--- a/lib/sqlalchemy/util/__init__.py
+++ b/lib/sqlalchemy/util/__init__.py
@@ -27,7 +27,7 @@ from langhelpers import iterate_attributes, class_hierarchy, \
     duck_type_collection, assert_arg_type, symbol, dictlike_iteritems,\
     classproperty, set_creation_order, warn_exception, warn, NoneType,\
     constructor_copy, methods_equivalent, chop_traceback, asint,\
-    generic_repr, counter
+    generic_repr, counter, PluginLoader
 
 from deprecations import warn_deprecated, warn_pending_deprecation, \
     deprecated, pending_deprecation
diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index d266c9664..9e5b0e4ad 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -52,6 +52,45 @@ def decorator(target):
         return update_wrapper(decorated, fn)
     return update_wrapper(decorate, target)
 
+class PluginLoader(object):
+    def __init__(self, group, auto_fn=None):
+        self.group = group
+        self.impls = {}
+        self.auto_fn = auto_fn
+
+    def load(self, name):
+        if name in self.impls:
+             return self.impls[name]()
+
+        if self.auto_fn:
+            loader = self.auto_fn(name)
+            if loader:
+                self.impls[name] = loader
+                return loader()
+
+        try:
+            import pkg_resources
+        except ImportError:
+            pass
+        else:
+            for impl in pkg_resources.iter_entry_points(
+                                self.group, name):
+                self.impls[name] = impl.load
+                return impl.load()
+
+        from sqlalchemy import exc
+        raise exc.ArgumentError(
+                "Can't load plugin: %s:%s" % 
+                (self.group, name))
+
+    def register(self, name, modulepath, objname):
+        def load():
+            mod = __import__(modulepath)
+            for token in modulepath.split(".")[1:]:
+                mod = getattr(mod, token)
+            return getattr(mod, objname)
+        self.impls[name] = load
+
 
 def get_cls_kwargs(cls):
     """Return the full set of inherited kwargs for the given `cls`.