Dispatch a blinker signal on scope change, instead of raising a warning

See https://github.com/idan/oauthlib/pull/265 for rationale.
In brief: raising any exception blows the stack, which is
inappropriate for a non-error state.

1 files changed, 41 insertions, 0 deletions

diff --git a/oauthlib/signals.py b/oauthlib/signals.py
new file mode 100644
index 0000000..2f86650
--- /dev/null
+++ b/oauthlib/signals.py
@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+"""
+    Implements signals based on blinker if available, otherwise
+    falls silently back to a noop. Shamelessly stolen from flask.signals:
+    https://github.com/mitsuhiko/flask/blob/master/flask/signals.py
+"""
+signals_available = False
+try:
+    from blinker import Namespace
+    signals_available = True
+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 = connected_to = _fail
+        del _fail
+
+# The namespace for code signals.  If you are not oauthlib code, do
+# not put signals in here.  Create your own namespace instead.
+_signals = Namespace()
+
+
+# Core signals.
+scope_changed = _signals.signal('scope-changed')