Robustness for lambdas, lambda statements

in order to accommodate relationship loaders
with lambda caching, a lot more is needed.  This is
a full refactor of the lambda system such that it
now has two levels of caching; the first level caches what
can be known from the __code__ element, then the next level
of caching is against the lambda itself and the contents
of __closure__.  This allows for the elements inside
the lambdas, like columns and entities, to change and
then be part of the cache key.  Lazy/selectinloads' use of
baked queries had to add distinct cache key elements,
which was attempted here but overall things needed to be
more robust than that.

This commit is broken out from the very long and sprawling
commit at Id6b5c03b1ce9ddb7b280f66792212a0ef0a1c541 .

Change-Id: I29a513c98917b1d503abfdd61e6b6e8800851aa8

1 files changed, 12 insertions, 37 deletions

diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index ca73a4392..8a506446d 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -32,8 +32,8 @@ from .base import NO_ARG
 from .base import PARSE_AUTOCOMMIT
 from .base import SingletonConstant
 from .coercions import _document_text_coercion
-from .traversals import _copy_internals
 from .traversals import _get_children
+from .traversals import HasCopyInternals
 from .traversals import MemoizedHasCacheKey
 from .traversals import NO_CACHE
 from .visitors import cloned_traverse
@@ -182,6 +182,7 @@ class ClauseElement(
     roles.SQLRole,
     SupportsWrappingAnnotations,
     MemoizedHasCacheKey,
+    HasCopyInternals,
     Traversible,
 ):
     """Base class for elements of a programmatically constructed SQL
@@ -372,35 +373,6 @@ class ClauseElement(
         """
         return traversals.compare(self, other, **kw)
 
-    def _copy_internals(self, omit_attrs=(), **kw):
-        """Reassign internal elements to be clones of themselves.
-
-        Called during a copy-and-traverse operation on newly
-        shallow-copied elements to create a deep copy.
-
-        The given clone function should be used, which may be applying
-        additional transformations to the element (i.e. replacement
-        traversal, cloned traversal, annotations).
-
-        """
-
-        try:
-            traverse_internals = self._traverse_internals
-        except AttributeError:
-            # user-defined classes may not have a _traverse_internals
-            return
-
-        for attrname, obj, meth in _copy_internals.run_generated_dispatch(
-            self, traverse_internals, "_generated_copy_internals_traversal"
-        ):
-            if attrname in omit_attrs:
-                continue
-
-            if obj is not None:
-                result = meth(self, attrname, obj, **kw)
-                if result is not None:
-                    setattr(self, attrname, result)
-
     def get_children(self, omit_attrs=(), **kw):
         r"""Return immediate child :class:`.visitors.Traversible`
         elements of this :class:`.visitors.Traversible`.
@@ -535,8 +507,6 @@ class ClauseElement(
         else:
             elem_cache_key = None
 
-        cache_hit = False
-
         if elem_cache_key:
             cache_key, extracted_params = elem_cache_key
             key = (
@@ -549,6 +519,7 @@ class ClauseElement(
             compiled_sql = compiled_cache.get(key)
 
             if compiled_sql is None:
+                cache_hit = dialect.CACHE_MISS
                 compiled_sql = self._compiler(
                     dialect,
                     cache_key=elem_cache_key,
@@ -559,7 +530,7 @@ class ClauseElement(
                 )
                 compiled_cache[key] = compiled_sql
             else:
-                cache_hit = True
+                cache_hit = dialect.CACHE_HIT
         else:
             extracted_params = None
             compiled_sql = self._compiler(
@@ -570,6 +541,11 @@ class ClauseElement(
                 schema_translate_map=schema_translate_map,
                 **kw
             )
+            cache_hit = (
+                dialect.CACHING_DISABLED
+                if compiled_cache is None
+                else dialect.NO_CACHE_KEY
+            )
 
         return compiled_sql, extracted_params, cache_hit
 
@@ -1343,10 +1319,7 @@ class BindParameter(roles.InElementRole, ColumnElement):
         if required is NO_ARG:
             required = value is NO_ARG and callable_ is None
         if value is NO_ARG:
-            self._value_required_for_cache = False
             value = None
-        else:
-            self._value_required_for_cache = True
 
         if quote is not None:
             key = quoted_name(key, quote)
@@ -1412,6 +1385,7 @@ class BindParameter(roles.InElementRole, ColumnElement):
         """Return a copy of this :class:`.BindParameter` with the given value
         set.
         """
+
         cloned = self._clone(maintain_key=maintain_key)
         cloned.value = value
         cloned.callable = None
@@ -1465,7 +1439,8 @@ class BindParameter(roles.InElementRole, ColumnElement):
             anon_map[idself] = id_ = str(anon_map.index)
             anon_map.index += 1
 
-        bindparams.append(self)
+        if bindparams is not None:
+            bindparams.append(self)
 
         return (
             id_,