Add --notify cli option

This is a synchronization helper for debugging functional tests in nvim. When
--notify is passed, the string "attached" will be printed to stdout as soon as
nvim is attached.

Author: tarruda

neovim/ui/cli.py

@@ -9,6 +9,7 @@
 
 @click.command(context_settings=dict(allow_extra_args=True))
 @click.option('--prog')
+@click.option('--notify', '-n', default=False, is_flag=True)
 @click.option('--gui', '-g', default=False, is_flag=True)
 @click.option('--listen', '-l')
 @click.option('--connect', '-c')
@@ -17,7 +18,7 @@
               type=click.Choice(['ncalls', 'tottime', 'percall', 'cumtime',
                                  'name', 'disable']))
 @click.pass_context
-def main(ctx, prog, gui, listen, connect, profile):
+def main(ctx, prog, notify, gui, listen, connect, profile):
     """Entry point."""
     address = connect or listen
 
@@ -65,7 +66,7 @@ def main(ctx, prog, gui, listen, connect, profile):
         from .tickit_ui import TickitUI
         ui = TickitUI()
     bridge = UIBridge()
-    bridge.connect(nvim, ui, profile if profile != 'disable' else None)
+    bridge.connect(nvim, ui, profile if profile != 'disable' else None, notify)
 
 
 if __name__ == '__main__':

neovim/ui/ui_bridge.py

@@ -1,4 +1,5 @@
 """Bridge for connecting a UI instance to nvim."""
+import sys
 from threading import Semaphore, Thread
 from traceback import format_exc
 
@@ -7,12 +8,13 @@ class UIBridge(object):
 
     """UIBridge class. Connects a Nvim instance to a UI class."""
 
-    def connect(self, nvim, ui, profile=None):
+    def connect(self, nvim, ui, profile=None, notify=False):
         """Connect nvim and the ui.
 
         This will start loops for handling the UI and nvim events while
         also synchronizing both.
         """
+        self._notify = notify
         self._error = None
         self._nvim = nvim
         self._ui = ui
@@ -76,6 +78,10 @@ def on_request(method, args):
 
         def on_notification(method, updates):
             def apply_updates():
+                if self._notify:
+                    sys.stdout.write('attached\n')
+                    sys.stdout.flush()
+                    self._notify = False
                 try:
                     for update in updates:
                         # import sys