Ensure CHECK constraint name is quoted for MySQL

Change-Id: Ib85de299c5f3c2631c64fe30006879ba274fca15
Fixes: #487

Author: zzzeek

alembic/ddl/mysql.py

@@ -342,7 +342,8 @@ def _mysql_drop_constraint(element, compiler, **kw):
         # DROP CONSTRAINT for MySQL/MariaDB, so we implement fully
         # here.
         return "ALTER TABLE %s DROP CONSTRAINT %s" % \
-            (compiler.preparer.format_table(constraint.table), constraint.name)
+            (compiler.preparer.format_table(constraint.table),
+             compiler.preparer.format_constraint(constraint))
     else:
         raise NotImplementedError(
             "No generic 'DROP CONSTRAINT' in MySQL - "

docs/build/unreleased/487.rst

@@ -0,0 +1,6 @@
+.. change::
+    :tags: bug, operations, mysql
+    :tickets: 487
+
+    Fixed bug in ``op.drop_constraint()`` for MySQL where
+    quoting rules would not be applied to the constraint name.

tests/test_mysql.py

@@ -174,6 +174,13 @@ def test_drop_fk(self):
             "ALTER TABLE t1 DROP FOREIGN KEY f1"
         )
 
+    def test_drop_fk_quoted(self):
+        context = op_fixture('mysql')
+        op.drop_constraint("MyFk", "MyTable", "foreignkey")
+        context.assert_(
+            "ALTER TABLE `MyTable` DROP FOREIGN KEY `MyFk`"
+        )
+
     def test_drop_constraint_primary(self):
         context = op_fixture('mysql')
         op.drop_constraint('primary', 't1', type_='primary')
@@ -188,13 +195,27 @@ def test_drop_unique(self):
             "ALTER TABLE t1 DROP INDEX f1"
         )
 
+    def test_drop_unique_quoted(self):
+        context = op_fixture('mysql')
+        op.drop_constraint("MyUnique", "MyTable", "unique")
+        context.assert_(
+            "ALTER TABLE `MyTable` DROP INDEX `MyUnique`"
+        )
+
     def test_drop_check(self):
         context = op_fixture('mysql')
         op.drop_constraint("f1", "t1", "check")
         context.assert_(
             "ALTER TABLE t1 DROP CONSTRAINT f1"
         )
 
+    def test_drop_check_quoted(self):
+        context = op_fixture('mysql')
+        op.drop_constraint("MyCheck", "MyTable", "check")
+        context.assert_(
+            "ALTER TABLE `MyTable` DROP CONSTRAINT `MyCheck`"
+        )
+
     def test_drop_unknown(self):
         op_fixture('mysql')
         assert_raises_message(