Fix #553

Ensure SourceMixin descendents shut down the source prior to closing.
Furthermore, make sure devices are closed before pin factory shuts down,
and that pins have a strong reference to their owning factory (to
prevent losing the factory before the pins).

gpiozero/devices.py

@@ -34,6 +34,7 @@ from .exc import (
     GPIOPinInUse,
     GPIODeviceClosed,
     PinFactoryFallback,
+    PinReservationsExist,
     )
 from .compat import frozendict
 
@@ -202,6 +203,20 @@ class Device(ValuesMixin, GPIOBase):
 
     @classmethod
     def _set_pin_factory(cls, new_factory):
+        reserved_devices = {
+            dev
+            for ref_list in cls._reservations.values()
+            for ref in ref_list
+            for dev in (ref(),)
+            if dev is not None
+        }
+        if new_factory is None:
+            for dev in reserved_devices:
+                dev.close()
+        elif reserved_devices:
+            raise PinReservationsExist(
+                "can't change factory while devices still hold pin "
+                "reservations (%r)" % dev)
         if cls._pin_factory is not None:
             cls._pin_factory.close()
         cls._pin_factory = new_factory

gpiozero/exc.py

@@ -145,6 +145,9 @@ class PinNoPins(PinError, RuntimeError):
 class PinInvalidPin(PinError, ValueError):
     "Error raised when an invalid pin specification is provided"
 
+class PinReservationsExist(PinError, RuntimeError):
+    "Error raised when pin factory is changed while reservations still exist"
+
 class GPIOZeroWarning(Warning):
     "Base class for all warnings in GPIO Zero"
 

gpiozero/mixins.py

@@ -70,10 +70,13 @@ class SourceMixin(object):
 
     def close(self):
         try:
-            super(SourceMixin, self).close()
             self.source = None
         except AttributeError:
             pass
+        try:
+            super(SourceMixin, self).close()
+        except AttributeError:
+            pass
 
     def _copy_values(self, source):
         for v in source:

gpiozero/pins/pi.py

@@ -9,10 +9,10 @@ str = type('')
 import io
 from threading import RLock
 from types import MethodType
-from weakref import ref, proxy
 try:
-    from weakref import WeakMethod
+    from weakref import ref, WeakMethod
 except ImportError:
+
     from ..compat import WeakMethod
 import warnings
 
@@ -216,7 +216,7 @@ class PiPin(Pin):
     """
     def __init__(self, factory, number):
         super(PiPin, self).__init__()
-        self._factory = proxy(factory)
+        self._factory = factory
         self._when_changed_lock = RLock()
         self._when_changed = None
         self._number = number