Move mapper and table arg merging to ModelMeta to eliminate usage of …

…declared_attr.

alchy/_compat.py

@@ -102,3 +102,10 @@ def __exit__(self, *args):
         BROKEN_PYPY_CTXMGR_EXIT = True
     except AssertionError:
         pass
+
+
+# Define classmethod_func(f) to retrieve the unbound function of classmethod f
+if sys.version_info[:2] >= (2, 7):
+    def classmethod_func(f): return f.__func__
+else:
+    def classmethod_func(f): return f.__get__(1).im_func

alchy/model.py

@@ -2,20 +2,16 @@
 """
 
 from sqlalchemy import inspect, orm
-from sqlalchemy.ext.declarative import (
-    declarative_base,
-    DeclarativeMeta,
-    declared_attr
-)
+from sqlalchemy.ext.declarative import declarative_base, DeclarativeMeta
 
 from . import query, events
 from .utils import (
     is_sequence,
     has_primary_key,
     camelcase_to_underscore,
     get_mapper_class,
-    merge_declarative_args,
-    unique
+    merge_mapper_args,
+    merge_table_args
 )
 from ._compat import iteritems
 
@@ -72,6 +68,18 @@ def __init__(cls, name, bases, dct):
 
             events.register(cls, dct)
 
+        base_dcts = [dct] + [base.__dict__ for base in bases]
+
+        # Merge __mapper_args__ from all base classes.
+        __mapper_args__ = merge_mapper_args(cls, base_dcts)
+        if __mapper_args__:
+            cls.__mapper_args__ = __mapper_args__
+
+        # Merge __table_args__ from all base classes.
+        __table_args__ = merge_table_args(cls, base_dcts)
+        if __table_args__:
+            cls.__table_args__ = __table_args__
+
 
 class ModelBase(object):
     """Base class for creating a declarative base for models.
@@ -123,33 +131,6 @@ class User(Model):
     query_class = query.QueryModel
     query = None
 
-    @declared_attr
-    def __table_args__(cls):  # pylint: disable=no-self-argument
-        # pylint: disable=no-member
-        args, kargs = merge_declarative_args(cls.__bases__, '__table_args__')
-        local_args, local_kargs = merge_declarative_args(
-            [cls], '__local_table_args__')
-
-        args = unique(args + local_args)
-        kargs.update(local_kargs)
-
-        # Append kargs onto end of args to adhere to SQLAlchemy requirements.
-        args.append(kargs)
-
-        return tuple(args)
-
-    @declared_attr
-    def __mapper_args__(cls):  # pylint: disable=no-self-argument
-        # pylint: disable=no-member
-        # NOTE: Mapper args are only allowed to be a dict so we ignore `args`.
-        _, kargs = merge_declarative_args(cls.__bases__, '__mapper_args__')
-        _, local_kargs = merge_declarative_args([cls],
-                                                '__local_mapper_args__')
-
-        kargs.update(local_kargs)
-
-        return kargs
-
     def __init__(self, *args, **kargs):
         """Initialize model instance by calling :meth:`update`."""
         self.update(*args, **kargs)

alchy/utils.py

@@ -9,7 +9,7 @@
 
 from sqlalchemy import Column
 
-from ._compat import string_types, iteritems
+from ._compat import string_types, iteritems, classmethod_func
 
 
 __all__ = [
@@ -92,20 +92,21 @@ def get_mapper_class(model, field):
     return mapper_class(getattr(model, field))
 
 
-def merge_declarative_args(base_classes, config_key):
-    """Given a list of base classes, merge declarative args identified by
+def merge_declarative_args(cls, base_dcts, config_key):
+    """Given a list of base dicts, merge declarative args identified by
     `config_key` into a single configuration object.
     """
-    configs = [getattr(base, config_key, None)
-               for base in reversed(base_classes)]
+    configs = [base.get(config_key) for base in reversed(base_dcts)]
     args = []
     kargs = {}
 
     for obj in configs:
         if not obj:
             continue
 
-        if callable(obj):
+        if isinstance(obj, classmethod):
+            obj = classmethod_func(obj)(cls)
+        elif callable(obj):
             obj = obj()
 
         if isinstance(obj, dict):
@@ -122,3 +123,35 @@ def merge_declarative_args(base_classes, config_key):
     args = unique(args)
 
     return (args, kargs)
+
+
+def merge_mapper_args(cls, base_dcts):
+    """Merge `__mapper_args__` from all base dictionaries and
+    `__local_mapper_args__` from first base into single inherited object.
+    """
+    _, kargs = merge_declarative_args(cls, base_dcts, '__mapper_args__')
+    _, local_kargs = merge_declarative_args(cls,
+                                            base_dcts[:1],
+                                            '__local_mapper_args__')
+
+    kargs.update(local_kargs)
+
+    return kargs
+
+
+def merge_table_args(cls, base_dcts):
+    """Merge `__table_args__` from all base dictionaries and
+    `__local_table_args__` from first base into single inherited object.
+    """
+    args, kargs = merge_declarative_args(cls, base_dcts, '__table_args__')
+    local_args, local_kargs = merge_declarative_args(cls,
+                                                     base_dcts[:1],
+                                                     '__local_table_args__')
+
+    args = unique(args + local_args)
+    kargs.update(local_kargs)
+
+    # Append kargs onto end of args to adhere to SQLAlchemy requirements.
+    args.append(kargs)
+
+    return tuple(args)

tests/test_model.py

@@ -466,7 +466,8 @@ class AbstractCM(object):
         class MixinCM(object):
             name = Column(types.String())
 
-            __table_args__ = (Index('idx_cm_name', 'name'),)
+            def __table_args__():
+                return (Index('idx_cm_name', 'name'),)
 
         class ObjCM(Model, MixinCM, AbstractCM):
             text = Column(types.Text())