String compiler can now literal compile datetime objects

Add ability to literal compile a :class:`DateTime`, :class:`Date`
or :class:"Time" when using the string dialect for debugging purposes.
This change does not impact real dialect implementation that retain
their current behavior.

Fixes: #5052
Change-Id: Ia3fad2be905c6d35b0106b9a2388c7508f067e90

1 files changed, 26 insertions, 0 deletions

diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index d0940decf..c44f07538 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -642,6 +642,26 @@ class DefaultDialect(interfaces.Dialect):
         return name
 
 
+class _RendersLiteral(object):
+    def literal_processor(self, dialect):
+        def process(value):
+            return "'%s'" % value
+
+        return process
+
+
+class _StrDateTime(_RendersLiteral, sqltypes.DateTime):
+    pass
+
+
+class _StrDate(_RendersLiteral, sqltypes.Date):
+    pass
+
+
+class _StrTime(_RendersLiteral, sqltypes.Time):
+    pass
+
+
 class StrCompileDialect(DefaultDialect):
 
     statement_compiler = compiler.StrSQLCompiler
@@ -658,6 +678,12 @@ class StrCompileDialect(DefaultDialect):
 
     supports_simple_order_by_label = True
 
+    colspecs = {
+        sqltypes.DateTime: _StrDateTime,
+        sqltypes.Date: _StrDate,
+        sqltypes.Time: _StrTime,
+    }
+
 
 class DefaultExecutionContext(interfaces.ExecutionContext):
     isinsert = False