Merge branch 'devel'2_5

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diff --git a/lib/_json.py b/lib/_json.py
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+"""Implementation of the JSON adaptation objects
+
+This module exists to avoid a circular import problem: pyscopg2.extras depends
+on psycopg2.extension, so I can't create the default JSON typecasters in
+extensions importing register_json from extras.
+"""
+
+# psycopg/_json.py - Implementation of the JSON adaptation objects
+#
+# Copyright (C) 2012 Daniele Varrazzo  <daniele.varrazzo@gmail.com>
+#
+# psycopg2 is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published
+# by the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# In addition, as a special exception, the copyright holders give
+# permission to link this program with the OpenSSL library (or with
+# modified versions of OpenSSL that use the same license as OpenSSL),
+# and distribute linked combinations including the two.
+#
+# You must obey the GNU Lesser General Public License in all respects for
+# all of the code used other than OpenSSL.
+#
+# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+# License for more details.
+
+import sys
+
+from psycopg2._psycopg import ISQLQuote, QuotedString
+from psycopg2._psycopg import new_type, new_array_type, register_type
+
+
+# import the best json implementation available
+if sys.version_info[:2] >= (2,6):
+    import json
+else:
+    try:
+        import simplejson as json
+    except ImportError:
+        json = None
+
+
+# oids from PostgreSQL 9.2
+JSON_OID = 114
+JSONARRAY_OID = 199
+
+class Json(object):
+    """
+    An `~psycopg2.extensions.ISQLQuote` wrapper to adapt a Python object to
+    :sql:`json` data type.
+
+    `!Json` can be used to wrap any object supported by the provided *dumps*
+    function.  If none is provided, the standard :py:func:`json.dumps()` is
+    used (`!simplejson` for Python < 2.6;
+    `~psycopg2.extensions.ISQLQuote.getquoted()` will raise `!ImportError` if
+    the module is not available).
+
+    """
+    def __init__(self, adapted, dumps=None):
+        self.adapted = adapted
+
+        if dumps is not None:
+            self._dumps = dumps
+        elif json is not None:
+            self._dumps = json.dumps
+        else:
+            self._dumps = None
+
+    def __conform__(self, proto):
+        if proto is ISQLQuote:
+            return self
+
+    def dumps(self, obj):
+        """Serialize *obj* in JSON format.
+
+        The default is to call `!json.dumps()` or the *dumps* function
+        provided in the constructor. You can override this method to create a
+        customized JSON wrapper.
+        """
+        dumps = self._dumps
+        if dumps is not None:
+            return dumps(obj)
+        else:
+            raise ImportError(
+                "json module not available: "
+                "you should provide a dumps function")
+
+    def getquoted(self):
+        s = self.dumps(self.adapted)
+        return QuotedString(s).getquoted()
+
+
+def register_json(conn_or_curs=None, globally=False, loads=None,
+        oid=None, array_oid=None):
+    """Create and register typecasters converting :sql:`json` type to Python objects.
+
+    :param conn_or_curs: a connection or cursor used to find the :sql:`json`
+        and :sql:`json[]` oids; the typecasters are registered in a scope
+        limited to this object, unless *globally* is set to `!True`. It can be
+        `!None` if the oids are provided
+    :param globally: if `!False` register the typecasters only on
+        *conn_or_curs*, otherwise register them globally
+    :param loads: the function used to parse the data into a Python object. If
+        `!None` use `!json.loads()`, where `!json` is the module chosen
+        according to the Python version (see above)
+    :param oid: the OID of the :sql:`json` type if known; If not, it will be
+        queried on *conn_or_curs*
+    :param array_oid: the OID of the :sql:`json[]` array type if known;
+        if not, it will be queried on *conn_or_curs*
+
+    The connection or cursor passed to the function will be used to query the
+    database and look for the OID of the :sql:`json` type. No query is
+    performed if *oid* and *array_oid* are provided.  Raise
+    `~psycopg2.ProgrammingError` if the type is not found.
+
+    """
+    if oid is None:
+        oid, array_oid = _get_json_oids(conn_or_curs)
+
+    JSON, JSONARRAY = _create_json_typecasters(oid, array_oid, loads)
+
+    register_type(JSON, not globally and conn_or_curs or None)
+
+    if JSONARRAY is not None:
+        register_type(JSONARRAY, not globally and conn_or_curs or None)
+
+    return JSON, JSONARRAY
+
+def register_default_json(conn_or_curs=None, globally=False, loads=None):
+    """
+    Create and register :sql:`json` typecasters for PostgreSQL 9.2 and following.
+
+    Since PostgreSQL 9.2 :sql:`json` is a builtin type, hence its oid is known
+    and fixed. This function allows specifying a customized *loads* function
+    for the default :sql:`json` type without querying the database.
+    All the parameters have the same meaning of `register_json()`.
+    """
+    return register_json(conn_or_curs=conn_or_curs, globally=globally,
+        loads=loads, oid=JSON_OID, array_oid=JSONARRAY_OID)
+
+def _create_json_typecasters(oid, array_oid, loads=None):
+    """Create typecasters for json data type."""
+    if loads is None:
+        if json is None:
+            raise ImportError("no json module available")
+        else:
+            loads = json.loads
+
+    def typecast_json(s, cur):
+        if s is None:
+            return None
+        return loads(s)
+
+    JSON = new_type((oid, ), 'JSON', typecast_json)
+    if array_oid is not None:
+        JSONARRAY = new_array_type((array_oid, ), "JSONARRAY", JSON)
+    else:
+        JSONARRAY = None
+
+    return JSON, JSONARRAY
+
+def _get_json_oids(conn_or_curs):
+    # lazy imports
+    from psycopg2.extensions import STATUS_IN_TRANSACTION
+    from psycopg2.extras import _solve_conn_curs
+
+    conn, curs = _solve_conn_curs(conn_or_curs)
+
+    # Store the transaction status of the connection to revert it after use
+    conn_status = conn.status
+
+    # column typarray not available before PG 8.3
+    typarray = conn.server_version >= 80300 and "typarray" or "NULL"
+
+    # get the oid for the hstore
+    curs.execute(
+        "SELECT t.oid, %s FROM pg_type t WHERE t.typname = 'json';"
+            % typarray)
+    r = curs.fetchone()
+
+    # revert the status of the connection as before the command
+    if (conn_status != STATUS_IN_TRANSACTION and not conn.autocommit):
+        conn.rollback()
+
+    if not r:
+        raise conn.ProgrammingError("json data type not found")
+
+    return r
+
+
+