Fixed error related to calling C typecasters from Python ones

ChangeLog

@@ -1,3 +1,8 @@
+2010-04-05  Federico Di Gregorio  <fog@initd.org>
+
+	* typecast.c: Fixed problem related to receiving None from Python
+	when a string was expected.
+
 2010-05-07  Daniele Varrazzo  <daniele.varrazzo@gmail.com>
 
 	* psycopg/adapter_datetime.c: Fixed TimestampFromTicks for second

psycopg/typecast.c

@@ -435,6 +435,15 @@ typecast_call(PyObject *obj, PyObject *args, PyObject *kwargs)
         return NULL;
     }
 
+    // If the string is not a string but a None value we're being called
+    // from a Python-defined caster. There is no need to convert, just
+    // return it.
+
+    if (string == Py_None) {
+        Py_INCREF(string);
+        return string;
+    }
+
     return typecast_cast(obj,
                          PyString_AsString(string), PyString_Size(string),
                          cursor);

psycopg2.cproj

@@ -198,6 +198,7 @@
     <None Include="sandbox\valgrind-python.supp" />
     <None Include="psycopg\green.h" />
     <None Include="doc\src\pool.rst" />
+    <None Include="sandbox\dec2float.py" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="psycopg\adapter_asis.c" />

sandbox/dec2float.py

@@ -0,0 +1,15 @@
+import psycopg2
+import psycopg2.extensions
+
+DEC2FLOAT = psycopg2.extensions.new_type(
+  psycopg2._psycopg.DECIMAL.values,
+  'DEC2FLOAT',
+  psycopg2.extensions.FLOAT)
+
+psycopg2.extensions.register_type(DEC2FLOAT)
+
+o = psycopg2.connect("dbname=test")
+c = o.cursor()
+c.execute("SELECT NULL::decimal(10,2)")
+n = c.fetchone()[0]
+print n, type(n)