From 9a031db8b90488afb59e0d6c8995398c88b6bc41 Mon Sep 17 00:00:00 2001
From: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Date: Mon, 3 Dec 2012 14:19:09 +0000
Subject: [PATCH] Fixed empty strings handling in composite caster

Closes ticket #141.
---
 NEWS                       |  1 +
 lib/extras.py              |  4 ++--
 tests/test_types_extras.py | 21 +++++++++++++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index 8f4f258c..0cdc3958 100644
--- a/NEWS
+++ b/NEWS
@@ -33,6 +33,7 @@ What's new in psycopg 2.4.5
   - Discard any result produced by 'executemany()' (ticket #133).
   - Fixed pickling of FixedOffsetTimezone objects (ticket #135).
   - Release the GIL around PQgetResult calls after COPY (ticket #140).
+  - Fixed empty strings handling in composite caster (ticket #141).
 
 
 What's new in psycopg 2.4.5
diff --git a/lib/extras.py b/lib/extras.py
index 5b45bdd1..22ae3f6e 100644
--- a/lib/extras.py
+++ b/lib/extras.py
@@ -852,9 +852,9 @@ class CompositeCaster(object):
         for m in self._re_tokenize.finditer(s):
             if m is None:
                 raise psycopg2.InterfaceError("can't parse type: %r" % s)
-            if m.group(1):
+            if m.group(1) is not None:
                 rv.append(None)
-            elif m.group(2):
+            elif m.group(2) is not None:
                 rv.append(self._re_undouble.sub(r"\1", m.group(2)))
             else:
                 rv.append(m.group(3))
diff --git a/tests/test_types_extras.py b/tests/test_types_extras.py
index 559d8c9e..944ab894 100755
--- a/tests/test_types_extras.py
+++ b/tests/test_types_extras.py
@@ -501,6 +501,7 @@ class AdaptTypeTestCase(unittest.TestCase):
             self.assertEqual(CompositeCaster.tokenize(s), v)
 
         ok("(,)", [None, None])
+        ok('(,"")', [None, ''])
         ok('(hello,,10.234,2010-11-11)', ['hello', None, '10.234', '2010-11-11'])
         ok('(10,"""")', ['10', '"'])
         ok('(10,",")', ['10', ','])
@@ -555,6 +556,26 @@ class AdaptTypeTestCase(unittest.TestCase):
             self.assertEqual(v.astring, "hello")
             self.assertEqual(v.adate, date(2011,1,2))
 
+    @skip_if_no_composite
+    def test_empty_string(self):
+        # issue #141
+        self._create_type("type_ss", [('s1', 'text'), ('s2', 'text')])
+        curs = self.conn.cursor()
+        psycopg2.extras.register_composite("type_ss", curs)
+
+        def ok(t):
+            curs.execute("select %s::type_ss", (t,))
+            rv = curs.fetchone()[0]
+            self.assertEqual(t, rv)
+
+        ok(('a', 'b'))
+        ok(('a', ''))
+        ok(('', 'b'))
+        ok(('a', None))
+        ok((None, 'b'))
+        ok(('', ''))
+        ok((None, None))
+
     @skip_if_no_composite
     def test_cast_nested(self):
         self._create_type("type_is",