Don't hope to encode stuff in an arbitrary encoding

libpq's PQescapeString will use the same encoding it has seen before in
a connection (static_client_encoding).

So I think I'll leave this feature here for people who know what is
doing, but won't really document it as a feature: it can't really work
in a generic way (unless adding some disgusting hack like creating a
fake connection with the encoding we want to call PQescapeStringConn
instead of PQescapeString).

NEWS

@@ -7,6 +7,7 @@ What's new in psycopg 2.6.2
 - Report the server response status on errors (such as :ticket:`#281`).
 - Raise `!NotSupportedError` on unhandled server response status
   (:ticket:`#352`).
+- Allow overriding string adapter encoding with no connection (:ticket:`#331`).
 - The `~psycopg2.extras.wait_select` callback allows interrupting a
   long-running query in an interactive shell using :kbd:`Ctrl-C`
   (:ticket:`#333`).

tests/test_quote.py

@@ -157,7 +157,7 @@ class QuotingTestCase(ConnectingTestCase):
 
 
 class TestQuotedString(ConnectingTestCase):
-    def test_encoding(self):
+    def test_encoding_from_conn(self):
         q = psycopg2.extensions.QuotedString('hi')
         self.assertEqual(q.encoding, 'latin1')
 
@@ -165,16 +165,17 @@ class TestQuotedString(ConnectingTestCase):
         q.prepare(self.conn)
         self.assertEqual(q.encoding, 'utf_8')
 
-
-class TestStringAdapter(ConnectingTestCase):
     def test_encoding_default(self):
         from psycopg2.extensions import adapt
         a = adapt("hello")
         self.assertEqual(a.encoding, 'latin1')
         self.assertEqual(a.getquoted(), "'hello'")
 
-        egrave = u'\xe8'
-        self.assertEqual(adapt(egrave).getquoted(), "'\xe8'")
+        # NOTE: we can't really test an encoding different from utf8, because
+        # when encoding without connection the libpq will use parameters from
+        # a previous one, so what would happens depends jn the tests run order.
+        # egrave = u'\xe8'
+        # self.assertEqual(adapt(egrave).getquoted(), "'\xe8'")
 
     def test_encoding_error(self):
         from psycopg2.extensions import adapt
@@ -183,6 +184,9 @@ class TestStringAdapter(ConnectingTestCase):
         self.assertRaises(UnicodeEncodeError, a.getquoted)
 
     def test_set_encoding(self):
+        # Note: this works-ish mostly in case when the standard db connection
+        # we test with is utf8, otherwise the encoding chosen by PQescapeString
+        # may give bad results.
         from psycopg2.extensions import adapt
         snowman = u"\u2603"
         a = adapt(snowman)