- store only MultipleClassMarkers inside of ModuleMarker, then

store ModuleMarkers for multiple roots, one for each token in a
module path.  this allows partial path resolution.
- docs to this effect

2 files changed, 71 insertions, 26 deletions

diff --git a/lib/sqlalchemy/ext/declarative/__init__.py b/lib/sqlalchemy/ext/declarative/__init__.py
index b3cecf6b0..bf6e6786e 100644
--- a/lib/sqlalchemy/ext/declarative/__init__.py
+++ b/lib/sqlalchemy/ext/declarative/__init__.py
@@ -146,7 +146,7 @@ expression functions like :func:`~sqlalchemy.sql.expression.desc` and
                              primaryjoin="Address.user_id==User.id")
 
 For the case where more than one module contains a class of the same name,
-string class names can also be specified as fully module-qualified paths
+string class names can also be specified as module-qualified paths
 within any of these string expressions::
 
     class User(Base):
@@ -156,9 +156,21 @@ within any of these string expressions::
                              primaryjoin="myapp.model.address.Address.user_id=="
                                             "myapp.model.user.User.id")
 
+The qualified path can be any partial path that removes ambiguity between
+the names.  For example, to disambiguate between
+``myapp.model.address.Address`` and ``myapp.model.lookup.Address``,
+we can specify ``address.Address`` or ``lookup.Address``::
+
+    class User(Base):
+        # ....
+        addresses = relationship("address.Address",
+                             order_by="desc(address.Address.email)",
+                             primaryjoin="address.Address.user_id=="
+                                            "User.id")
+
 .. versionadded:: 0.8
-   Fully module-qualified paths can be used when specifying string arguments
-   with Declarative.
+   module-qualified paths can be used when specifying string arguments
+   with Declarative, in order to specify specific modules.
 
 Two alternatives also exist to using string-based attributes.  A lambda
 can also be used, which will be evaluated after all mappers have been
diff --git a/lib/sqlalchemy/ext/declarative/clsregistry.py b/lib/sqlalchemy/ext/declarative/clsregistry.py
index 08b487db3..47450c5b7 100644
--- a/lib/sqlalchemy/ext/declarative/clsregistry.py
+++ b/lib/sqlalchemy/ext/declarative/clsregistry.py
@@ -38,14 +38,28 @@ def add_class(classname, cls):
         cls._decl_class_registry[classname] = cls
 
     try:
-        module = cls._decl_class_registry['_sa_module_registry']
+        root_module = cls._decl_class_registry['_sa_module_registry']
     except KeyError:
         cls._decl_class_registry['_sa_module_registry'] = \
-            module = _ModuleMarker('_sa_module_registry', None)
-    for token in cls.__module__.split("."):
-        module = module.get_module(token)
+            root_module = _ModuleMarker('_sa_module_registry', None)
+
+    tokens = cls.__module__.split(".")
+
+    # build up a tree like this:
+    # modulename:  myapp.snacks.nuts
+    #
+    # myapp->snack->nuts->(classes)
+    # snack->nuts->(classes)
+    # nuts->(classes)
+    #
+    # this allows partial token paths to be used.
+    while tokens:
+        token = tokens.pop(0)
+        module = root_module.get_module(token)
+        for token in tokens:
+            module = module.get_module(token)
+        module.add_class(classname, cls)
 
-    module.add_class(classname, cls)
 
 class _MultipleClassMarker(object):
     """refers to multiple classes of the same name
@@ -53,7 +67,8 @@ class _MultipleClassMarker(object):
 
     """
 
-    def __init__(self, classes):
+    def __init__(self, classes, on_remove=None):
+        self.on_remove = on_remove
         self.contents = set([
                 weakref.ref(item, self._remove_item) for item in classes])
         _registries.add(self)
@@ -61,12 +76,14 @@ class _MultipleClassMarker(object):
     def __iter__(self):
         return (ref() for ref in self.contents)
 
-    def attempt_get(self, key):
+    def attempt_get(self, path, key):
         if len(self.contents) > 1:
             raise exc.InvalidRequestError(
-                "Multiple classes with the classname "
-                "%r are in the registry of this declarative "
-                "base. Please use a fully module-qualified path." % key)
+                "Multiple classes found for path \"%s\" "
+                "in the registry of this declarative "
+                "base. Please use a fully module-qualified path." %
+                (".".join(path + [key]))
+            )
         else:
             ref = list(self.contents)[0]
             cls = ref()
@@ -78,8 +95,20 @@ class _MultipleClassMarker(object):
         self.contents.remove(ref)
         if not self.contents:
             _registries.discard(self)
+            if self.on_remove:
+                self.on_remove()
 
-    def add_item(self, item, base):
+    def add_item(self, item):
+        modules = set([cls().__module__ for cls in self.contents])
+        if item.__module__ in modules:
+            util.warn(
+                "This declarative base already contains a class with the "
+                "same class name and module name as %s.%s, and will "
+                "be replaced in the string-lookup table." % (
+                    item.__module__,
+                    item.__name__
+                )
+            )
         self.contents.add(weakref.ref(item, self._remove_item))
 
 class _ModuleMarker(object):
@@ -92,13 +121,17 @@ class _ModuleMarker(object):
         self.name = name
         self.contents = {}
         self.mod_ns = _ModNS(self)
+        if self.parent:
+            self.path = self.parent.path + [self.name]
+        else:
+            self.path = []
         _registries.add(self)
 
     def __contains__(self, name):
         return name in self.contents
 
     def __getitem__(self, name):
-        return self.contents[name]()
+        return self.contents[name]
 
     def _remove_item(self, name):
         self.contents.pop(name, None)
@@ -112,20 +145,20 @@ class _ModuleMarker(object):
     def get_module(self, name):
         if name not in self.contents:
             marker = _ModuleMarker(name, self)
-            self.contents[name] = lambda: marker
+            self.contents[name] = marker
         else:
-            marker = self.contents[name]()
+            marker = self.contents[name]
         return marker
 
     def add_class(self, name, cls):
         if name in self.contents:
-            util.warn(
-                "This declarative base already contains a class with the "
-                "same class name and module name as %r, and will be replaced "
-                "in the string-lookup table." % cls)
+            existing = self.contents[name]
+            existing.add_item(cls)
+        else:
+            existing = self.contents[name] = \
+                    _MultipleClassMarker([cls],
+                        on_remove=lambda: self._remove_item(name))
 
-        self.contents[name] = weakref.ref(cls,
-                            lambda ref: self._remove_item(name))
 
 
 class _ModNS(object):
@@ -138,12 +171,12 @@ class _ModNS(object):
         except KeyError:
             pass
         else:
-            value = value()
             if value is not None:
                 if isinstance(value, _ModuleMarker):
                     return value.mod_ns
                 else:
-                    return value
+                    assert isinstance(value, _MultipleClassMarker)
+                    return value.attempt_get(self.__parent.path, key)
         raise AttributeError("Module %r has no mapped classes "
                     "registered under the name %r" % (self.__parent.name, key))
 
@@ -179,7 +212,7 @@ class _GetTable(object):
 
 def _determine_container(key, value):
     if isinstance(value, _MultipleClassMarker):
-        value = value.attempt_get(key)
+        value = value.attempt_get([], key)
     return _GetColumns(value)
 
 def _resolver(cls, prop):