Annotate session-bind-lookup entity in Query-produced selectables

Added new entity-targeting capabilities to the :class:`.Query` object to
help with the case where the :class:`.Session` is using a bind dictionary
against mapped classes, rather than a single bind, and the :class:`.Query`
is against a Core statement that was ultimately generated from a method
such as :meth:`.Query.subquery`; a deep search is performed to locate
any ORM entity related to the query in order to locate a mapper if
one is not otherwise present.

Fixes: #4829
Change-Id: I95cf325a5aba21baec4b313246c6f4d692284820

1 files changed, 73 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/annotation.py b/lib/sqlalchemy/sql/annotation.py
index 7fc9245ab..a0264845e 100644
--- a/lib/sqlalchemy/sql/annotation.py
+++ b/lib/sqlalchemy/sql/annotation.py
@@ -15,8 +15,80 @@ from . import operators
 from .. import util
 
 
+class SupportsCloneAnnotations(object):
+    _annotations = util.immutabledict()
+
+    def _annotate(self, values):
+        """return a copy of this ClauseElement with annotations
+        updated by the given dictionary.
+
+        """
+        new = self._clone()
+        new._annotations = new._annotations.union(values)
+        return new
+
+    def _with_annotations(self, values):
+        """return a copy of this ClauseElement with annotations
+        replaced by the given dictionary.
+
+        """
+        new = self._clone()
+        new._annotations = util.immutabledict(values)
+        return new
+
+    def _deannotate(self, values=None, clone=False):
+        """return a copy of this :class:`.ClauseElement` with annotations
+        removed.
+
+        :param values: optional tuple of individual values
+         to remove.
+
+        """
+        if clone or self._annotations:
+            # clone is used when we are also copying
+            # the expression for a deep deannotation
+            new = self._clone()
+            new._annotations = {}
+            return new
+        else:
+            return self
+
+
+class SupportsWrappingAnnotations(object):
+    def _annotate(self, values):
+        """return a copy of this ClauseElement with annotations
+        updated by the given dictionary.
+
+        """
+        return Annotated(self, values)
+
+    def _with_annotations(self, values):
+        """return a copy of this ClauseElement with annotations
+        replaced by the given dictionary.
+
+        """
+        return Annotated(self, values)
+
+    def _deannotate(self, values=None, clone=False):
+        """return a copy of this :class:`.ClauseElement` with annotations
+        removed.
+
+        :param values: optional tuple of individual values
+         to remove.
+
+        """
+        if clone:
+            # clone is used when we are also copying
+            # the expression for a deep deannotation
+            return self._clone()
+        else:
+            # if no clone, since we have no annotations we return
+            # self
+            return self
+
+
 class Annotated(object):
-    """clones a ClauseElement and applies an 'annotations' dictionary.
+    """clones a SupportsAnnotated and applies an 'annotations' dictionary.
 
     Unlike regular clones, this clone also mimics __hash__() and
     __cmp__() of the original element so that it takes its place