Added appcontext_pushed and appcontext_popped signals

CHANGES

@@ -70,6 +70,7 @@ Release date to be decided.
 - Added the ``JSONIFY_PRETTYPRINT_REGULAR`` configuration variable.
 - Flask now orders JSON keys by default to not trash HTTP caches due to
   different hash seeds between different workers.
+- Added `appcontext_pushed` and `appcontext_popped` signals.
 
 Version 0.9
 -----------

docs/api.rst

@@ -535,7 +535,22 @@ Signals
    This signal is sent when the application is tearing down the
    application context.  This is always called, even if an error happened.
    An `exc` keyword argument is passed with the exception that caused the
-   teardown.
+   teardown.  The sender is the application.
+
+.. data:: appcontext_pushed
+
+   This signal is sent when an application context is pushed.  The sender
+   is the application.
+
+   .. versionadded:: 0.10
+
+.. data:: appcontext_popped
+
+   This signal is sent when an application context is popped.  The sender
+   is the application.  This usually falls in line with the
+   :data:`appcontext_tearing_down` signal.
+
+   .. versionadded:: 0.10
 
 .. data:: message_flashed
 

docs/signals.rst

@@ -291,6 +291,45 @@ The following signals exist in Flask:
    This will also be passed an `exc` keyword argument that has a reference
    to the exception that caused the teardown if there was one.
 
+.. data:: flask.appcontext_pushed
+   :noindex:
+
+   This signal is sent when an application context is pushed.  The sender
+   is the application.  This is usually useful for unittests in order to
+   temporarily hook in information.  For instance it can be used to
+   set a resource early onto the `g` object.
+
+   Example usage::
+
+        from contextlib import contextmanager
+        from flask import appcontext_pushed
+
+        @contextmanager
+        def user_set(app, user):
+            def handler(sender, **kwargs):
+                g.user = user
+            with appcontext_pushed.connected_to(handler, app):
+                yield
+
+   And in the testcode::
+
+        def test_user_me(self):
+            with user_set(app, 'john'):
+                c = app.test_client()
+                resp = c.get('/users/me')
+                assert resp.data == 'username=john'
+
+   .. versionadded:: 0.10
+
+.. data:: appcontext_popped
+
+   This signal is sent when an application context is popped.  The sender
+   is the application.  This usually falls in line with the
+   :data:`appcontext_tearing_down` signal.
+
+   .. versionadded:: 0.10
+
+
 .. data:: flask.message_flashed
    :noindex:
 

flask/__init__.py

@@ -34,7 +34,8 @@ from .templating import render_template, render_template_string
 # the signals
 from .signals import signals_available, template_rendered, request_started, \
      request_finished, got_request_exception, request_tearing_down, \
-     appcontext_tearing_down, message_flashed
+     appcontext_tearing_down, appcontext_pushed, \
+     appcontext_popped, message_flashed
 
 # We're not exposing the actual json module but a convenient wrapper around
 # it.

flask/ctx.py

@@ -18,6 +18,7 @@ from werkzeug.exceptions import HTTPException
 
 from .globals import _request_ctx_stack, _app_ctx_stack
 from .module import blueprint_is_module
+from .signals import appcontext_pushed, appcontext_popped
 
 
 class _AppCtxGlobals(object):
@@ -166,6 +167,7 @@ class AppContext(object):
         """Binds the app context to the current context."""
         self._refcnt += 1
         _app_ctx_stack.push(self)
+        appcontext_pushed.send(self.app)
 
     def pop(self, exc=None):
         """Pops the app context."""
@@ -177,6 +179,7 @@ class AppContext(object):
         rv = _app_ctx_stack.pop()
         assert rv is self, 'Popped wrong app context.  (%r instead of %r)' \
             % (rv, self)
+        appcontext_popped.send(self.app)
 
     def __enter__(self):
         self.push()

flask/signals.py

@@ -50,4 +50,6 @@ request_finished = _signals.signal('request-finished')
 request_tearing_down = _signals.signal('request-tearing-down')
 got_request_exception = _signals.signal('got-request-exception')
 appcontext_tearing_down = _signals.signal('appcontext-tearing-down')
+appcontext_pushed = _signals.signal('appcontext-pushed')
+appcontext_popped = _signals.signal('appcontext-popped')
 message_flashed = _signals.signal('message-flashed')

flask/testsuite/signals.py

@@ -96,6 +96,30 @@ class SignalsTestCase(FlaskTestCase):
         finally:
             flask.got_request_exception.disconnect(record, app)
 
+    def test_appcontext_signals(self):
+        app = flask.Flask(__name__)
+        recorded = []
+        def record_push(sender, **kwargs):
+            recorded.append('push')
+        def record_pop(sender, **kwargs):
+            recorded.append('push')
+
+        @app.route('/')
+        def index():
+            return 'Hello'
+
+        flask.appcontext_pushed.connect(record_push, app)
+        flask.appcontext_popped.connect(record_pop, app)
+        try:
+            with app.test_client() as c:
+                rv = c.get('/')
+                self.assert_equal(rv.data, b'Hello')
+                self.assert_equal(recorded, ['push'])
+            self.assert_equal(recorded, ['push', 'pop'])
+        finally:
+            flask.appcontext_pushed.disconnect(record_push, app)
+            flask.appcontext_popped.disconnect(record_pop, app)
+
     def test_flash_signal(self):
         app = flask.Flask(__name__)
         app.config['SECRET_KEY'] = 'secret'