- Fix bug in naming convention feature where using a check

constraint convention that includes ``constraint_name`` would
then force all :class:`.Boolean` and :class:`.Enum` types to
require names as well, as these implicitly create a
constraint, even if the ultimate target backend were one that does
not require generation of the constraint such as Postgresql.
The mechanics of naming conventions for these particular
constraints has been reorganized such that the naming
determination is done at DDL compile time, rather than at
constraint/table construction time.
fixes #3067

1 files changed, 23 insertions, 15 deletions

diff --git a/lib/sqlalchemy/sql/naming.py b/lib/sqlalchemy/sql/naming.py
index d05054bc6..bb838c542 100644
--- a/lib/sqlalchemy/sql/naming.py
+++ b/lib/sqlalchemy/sql/naming.py
@@ -14,7 +14,7 @@ from .schema import Constraint, ForeignKeyConstraint, PrimaryKeyConstraint, \
                 UniqueConstraint, CheckConstraint, Index, Table, Column
 from .. import event, events
 from .. import exc
-from .elements import _truncated_label
+from .elements import _truncated_label, _defer_name, _defer_none_name
 import re
 
 class conv(_truncated_label):
@@ -77,12 +77,12 @@ class ConventionDict(object):
             return list(self.const.columns)[idx]
 
     def _key_constraint_name(self):
-        if not self._const_name:
+        if isinstance(self._const_name, (type(None), _defer_none_name)):
             raise exc.InvalidRequestError(
-                    "Naming convention including "
-                    "%(constraint_name)s token requires that "
-                    "constraint is explicitly named."
-                )
+                "Naming convention including "
+                "%(constraint_name)s token requires that "
+                "constraint is explicitly named."
+            )
         if not isinstance(self._const_name, conv):
             self.const.name = None
         return self._const_name
@@ -144,6 +144,17 @@ def _get_convention(dict_, key):
     else:
         return None
 
+def _constraint_name_for_table(const, table):
+    metadata = table.metadata
+    convention = _get_convention(metadata.naming_convention, type(const))
+    if convention is not None and (
+            const.name is None or not isinstance(const.name, conv) and
+                "constraint_name" in convention
+        ):
+        return conv(
+                convention % ConventionDict(const, table,
+                                metadata.naming_convention)
+                )
 
 @event.listens_for(Constraint, "after_parent_attach")
 @event.listens_for(Index, "after_parent_attach")
@@ -156,12 +167,9 @@ def _constraint_name(const, table):
                     lambda col, table: _constraint_name(const, table)
                 )
     elif isinstance(table, Table):
-        metadata = table.metadata
-        convention = _get_convention(metadata.naming_convention, type(const))
-        if convention is not None:
-            if const.name is None or "constraint_name" in convention:
-                newname = conv(
-                            convention % ConventionDict(const, table, metadata.naming_convention)
-                            )
-                if const.name is None:
-                    const.name = newname
+        if isinstance(const.name, (conv, _defer_name)):
+            return
+
+        newname = _constraint_name_for_table(const, table)
+        if newname is not None:
+            const.name = newname