Added support for signals

flask/signals.py

@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+"""
+    flask.signals
+    ~~~~~~~~~~~~~
+
+    Implements signals based on blinker if available, otherwise
+    falls silently back to a noop
+
+    :copyright: (c) 2010 by Armin Ronacher.
+    :license: BSD, see LICENSE for more details.
+"""
+signals_available = False
+try:
+    from blinker import Namespace
+    signals_available = True
+    _signals = Namespace()
+except ImportError:
+    class Namespace(object):
+        def signal(self, name, doc=None):
+            return _FakeSignal(name, doc)
+    class _FakeSignal(object):
+        """If blinker is unavailable, create a fake class with the same
+        interface that allows sending of signals but will fail with an
+        error on anything else.  Instead of doing anything on send, it
+        will just ignore the arguments and do nothing instead.
+        """
+
+        def __init__(self, name, doc=None):
+            self.name = name
+            self.__doc__ = doc
+        def _fail(self, *args, **kwargs):
+            raise RuntimeError('signalling support is unavailable '
+                               'because the blinker library is '
+                               'not installed.')
+        send = lambda *a, **kw: None
+        connect = disconnect = has_receivers_for = receivers_for = \
+            temporarily_connected_to = _fail
+        del _fail
+
+# the namespace for code signals.  If you are not flask code, do
+# not put signals in here.  Create your own namespace instead.
+_signals = Namespace()
+
+
+# core signals.  For usage examples grep the sourcecode or consult
+# the API documentation in docs/api.rst as well as docs/signals.rst
+template_rendered = _signals.signal('template-rendered')
+request_started = _signals.signal('request-started')
+request_finished = _signals.signal('request-finished')
+got_request_exception = _signals.signal('got-request-exception')