[#400] Dynamic logic to infer procedures/hooks arguments.

This allows procedures and event hooks to have more flexible signatures.
Along the lines of:

```python
@when(SomeEvent)
def hook(event):
  ...

@when(SomeOtherEvent)
def hook2():
  ...
```

Instead of supporting only the full context spec:

```python
@when(SomeEvent)
def hook(event, **ctx):
  ...
```

Closes: #400

README.md

@@ -537,7 +537,7 @@ against partial event arguments are also possible, and relational operators are
 supported as well. For example:
 
 ```python
-from platypush import hook
+from platypush import when
 from platypush.message.event.sensor import SensorDataChangeEvent
 
 @when(SensorDataChangeEvent, data=1):

examples/config/hook.py

@@ -1,9 +1,13 @@
-# A more versatile way to define event hooks than the YAML format of `config.yaml` is through native Python scripts.
-# You can define hooks as simple Python functions that use the `platypush.event.hook.hook` decorator to specify on
-# which event type they should be called, and optionally on which event attribute values.
+# A more versatile way to define event hooks than the YAML format of
+# `config.yaml` is through native Python scripts. You can define hooks as simple
+# Python functions that use the `platypush.event.hook.hook` decorator to specify
+# on which event type they should be called, and optionally on which event
+# attribute values.
 #
-# Event hooks should be stored in Python files under `~/.config/platypush/scripts`. All the functions that use the
-# @when decorator will automatically be discovered and imported as event hooks into the platform at runtime.
+# Event hooks should be stored in Python files under
+# `~/.config/platypush/scripts`. All the functions that use the @when decorator
+# will automatically be discovered and imported as event hooks into the platform
+# at runtime.
 
 # `run` is a utility function that runs a request by name (e.g. `light.hue.on`).
 from platypush import when, run
@@ -16,12 +20,14 @@ from platypush.message.event.assistant import (
 
 
 @when(SpeechRecognizedEvent, phrase='play ${title} by ${artist}')
-def on_music_play_command(event, title=None, artist=None, **context):
+def on_music_play_command(event, title=None, artist=None):
     """
-    This function will be executed when a SpeechRecognizedEvent with `phrase="play the music"` is triggered.
-    `event` contains the event object and `context` any key-value info from the running context.
-    Note that in this specific case we can leverage the token-extraction feature of SpeechRecognizedEvent through
-    ${} that operates on regex-like principles to extract any text that matches the pattern into context variables.
+    This function will be executed when a SpeechRecognizedEvent with
+    `phrase="play the music"` is triggered. `event` contains the event object
+    and `context` any key-value info from the running context. Note that in this
+    specific case we can leverage the token-extraction feature of
+    SpeechRecognizedEvent through ${} that operates on regex-like principles to
+    extract any text that matches the pattern into context variables.
     """
     results = run(
         'music.mpd.search',
@@ -31,16 +37,17 @@ def on_music_play_command(event, title=None, artist=None, **context):
         },
     )
 
-    if results:
+    if results and results[0]:
         run('music.mpd.play', results[0]['file'])
     else:
         run('tts.say', "I can't find any music matching your query")
 
 
 @when(ConversationStartEvent)
-def on_conversation_start(event, **context):
+def on_conversation_start():
     """
-    A simple hook that gets invoked when a new conversation starts with a voice assistant and simply pauses the music
-    to make sure that your speech is properly detected.
+    A simple hook that gets invoked when a new conversation starts with a voice
+    assistant and simply pauses the music to make sure that your speech is
+    properly detected.
     """
     run('music.mpd.pause_if_playing')

platypush/common/__init__.py

@@ -1,7 +1,7 @@
 import inspect
 import logging
 import os
-from typing import Any, Callable
+from typing import Any, Callable, Mapping, Sequence, Tuple
 
 from platypush.utils.manifest import Manifest
 
@@ -10,6 +10,22 @@ from ._types import StoppableThread
 logger = logging.getLogger('platypush')
 
 
+def _build_args(
+    func: Callable, *args, **kwargs
+) -> Tuple[Sequence[Any], Mapping[str, Any]]:
+    spec = inspect.getfullargspec(func)
+    func_args = args if spec.varargs else args[: len(spec.args)]
+    func_kwargs = (
+        kwargs
+        if spec.varkw
+        else {
+            arg: kwargs[arg] for arg in [*spec.args, *spec.kwonlyargs] if arg in kwargs
+        }
+    )
+
+    return func_args, func_kwargs
+
+
 def exec_wrapper(f: Callable[..., Any], *args, **kwargs):
     """
     Utility function that runs a callable with its arguments, wraps its
@@ -17,8 +33,10 @@ def exec_wrapper(f: Callable[..., Any], *args, **kwargs):
     """
     from platypush import Response
 
+    func_args, func_kwargs = _build_args(f, *args, **kwargs)
+
     try:
-        ret = f(*args, **kwargs)
+        ret = f(*func_args, **func_kwargs)
         if isinstance(ret, Response):
             return ret
 

platypush/event/hook.py

@@ -179,9 +179,17 @@ class EventHook:
         result = self.matches_event(event)
 
         if result.is_match:
-            logger.info('Running hook %s triggered by an event', self.name)
+            logger.info(
+                'Running hook `%s` triggered by a `%s` event',
+                self.name,
+                f'{event.__module__}.{event.__class__.__name__}',
+            )
+
             threading.Thread(
-                target=_thread_func, name='Event-' + self.name, args=(result,)
+                target=_thread_func,
+                name='Event-' + self.name,
+                args=(result,),
+                daemon=True,
             ).start()