- Custom dialects that implement :class:`.GenericTypeCompiler` can

now be constructed such that the visit methods receive an indication
of the owning expression object, if any.  Any visit method that
accepts keyword arguments (e.g. ``**kw``) will in most cases
receive a keyword argument ``type_expression``, referring to the
expression object that the type is contained within.  For columns
in DDL, the dialect's compiler class may need to alter its
``get_column_specification()`` method to support this as well.
The ``UserDefinedType.get_col_spec()`` method will also receive
``type_expression`` if it provides ``**kw`` in its argument
signature.
fixes #3074

2 files changed, 28 insertions, 1 deletions

diff --git a/lib/sqlalchemy/util/__init__.py b/lib/sqlalchemy/util/__init__.py
index c23b0196f..ceee18d86 100644
--- a/lib/sqlalchemy/util/__init__.py
+++ b/lib/sqlalchemy/util/__init__.py
@@ -36,7 +36,7 @@ from .langhelpers import iterate_attributes, class_hierarchy, \
     generic_repr, counter, PluginLoader, hybridproperty, hybridmethod, \
     safe_reraise,\
     get_callable_argspec, only_once, attrsetter, ellipses_string, \
-    warn_limited, map_bits, MemoizedSlots
+    warn_limited, map_bits, MemoizedSlots, EnsureKWArgType
 
 from .deprecations import warn_deprecated, warn_pending_deprecation, \
     deprecated, pending_deprecation, inject_docstring_text
diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 22b6ad4ca..5a938501a 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -1348,6 +1348,7 @@ def chop_traceback(tb, exclude_prefix=_UNITTEST_RE, exclude_suffix=_SQLA_RE):
 
 NoneType = type(None)
 
+
 def attrsetter(attrname):
     code = \
         "def set(obj, value):"\
@@ -1355,3 +1356,29 @@ def attrsetter(attrname):
     env = locals().copy()
     exec(code, env)
     return env['set']
+
+
+class EnsureKWArgType(type):
+    """Apply translation of functions to accept **kw arguments if they
+    don't already.
+
+    """
+    def __init__(cls, clsname, bases, clsdict):
+        fn_reg = cls.ensure_kwarg
+        if fn_reg:
+            for key in clsdict:
+                m = re.match(fn_reg, key)
+                if m:
+                    fn = clsdict[key]
+                    spec = inspect.getargspec(fn)
+                    if not spec.keywords:
+                        clsdict[key] = wrapped = cls._wrap_w_kw(fn)
+                        setattr(cls, key, wrapped)
+        super(EnsureKWArgType, cls).__init__(clsname, bases, clsdict)
+
+    def _wrap_w_kw(self, fn):
+
+        def wrap(*arg, **kw):
+            return fn(*arg)
+        return update_wrapper(wrap, fn)
+