Exclude eq and ne from associative operators

The "eq" and "ne" operators are no longer part of the list of
"associative" operators, while they remain considered to be
"commutative".  This allows an expression like ``(x == y) == z``
to be maintained at the SQL level with parenthesis.  Pull request
courtesy John Passaro.

Fixes: #3799
Change-Id: I3759d8987b35649d7418b6524316c9e70c857e68
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/308

diff --git a/doc/build/changelog/changelog_11.rst b/doc/build/changelog/changelog_11.rst
index a0970348911e60d784006429616a64802bfcb2f5..4693eda29b4a6256a5d05d1196b2edb34ac346d9 100644 (file)
--- a/doc/build/changelog/changelog_11.rst
+++ b/doc/build/changelog/changelog_11.rst
@@ -21,6 +21,16 @@
 .. changelog::
     :version: 1.1.0
 
+    .. change::
+        :tags: bug, sql
+        :tickets: 3799
+
+        The "eq" and "ne" operators are no longer part of the list of
+        "associative" operators, while they remain considered to be
+        "commutative".  This allows an expression like ``(x == y) == z``
+        to be maintained at the SQL level with parenthesis.  Pull request
+        courtesy John Passaro.
+
     .. change::
         :tags: bug, orm
         :tickets: 3788

diff --git a/lib/sqlalchemy/sql/operators.py b/lib/sqlalchemy/sql/operators.py
index bf470710db7bce229b71d2869e63a41236558d28..14260668045c1f46074ed38d16c321cd07225b1c 100644 (file)
--- a/lib/sqlalchemy/sql/operators.py
+++ b/lib/sqlalchemy/sql/operators.py
@@ -917,7 +917,7 @@ def mirror(op):
     return _mirror.get(op, op)
 
 
-_associative = _commutative.union([concat_op, and_, or_])
+_associative = _commutative.union([concat_op, and_, or_]).difference([eq, ne])
 
 _natural_self_precedent = _associative.union([
     getitem, json_getitem_op, json_path_getitem_op])

diff --git a/test/sql/test_operators.py b/test/sql/test_operators.py
index b6e80de4bad82d8f72c80d8c1f71e299abb09615..99f8a10ca3c605a119284174edea830fe63dc450 100644 (file)
--- a/test/sql/test_operators.py
+++ b/test/sql/test_operators.py
@@ -1538,6 +1538,14 @@ class OperatorAssociativityTest(fixtures.TestBase, testing.AssertsCompiledSQL):
         f = column('f')
         self.assert_compile(f / (f / (f - f)), "f / (f / (f - f))")
 
+    def test_associativity_22(self):
+        f = column('f')
+        self.assert_compile((f==f) == f, '(f = f) = f')
+
+    def test_associativity_23(self):
+        f = column('f')
+        self.assert_compile((f!=f) != f, '(f != f) != f')
+
 
 class IsDistinctFromTest(fixtures.TestBase, testing.AssertsCompiledSQL):
     __dialect__ = 'default'