Replace dynamic use of "on_trait_change" handlers with "observe" (#373)

* DEV : Replace dynamic on_trait_change handlers with observe

This commit replaces the use of dynamic on_trait_change handlers e.g.
(object.on_trait_change(...)) with the use of observe
(object.observe(...)).

With these changes, the transition of traits-futures from
on_trait_change to observe is complete.

fixes #356

	modified:   traits_futures/asyncio/event_loop_helper.py
	modified:   traits_futures/qt/event_loop_helper.py
	modified:   traits_futures/tests/common_future_tests.py
	modified:   traits_futures/tests/traits_executor_tests.py
	modified:   traits_futures/wx/event_loop_helper.py

* DOC : Document the dependence on traits>= 6.2.0

	modified:   docs/source/changes.rst
	modified:   setup.py

docs/source/changes.rst

@@ -34,6 +34,7 @@ of Traits Futures.
 Other Changes
 ~~~~~~~~~~~~~
 
+* Traits Futures now requires Traits 6.2.0 or later.
 * Python 3.5 is no longer supported. Traits Futures requires Python 3.6
   or later.
 

setup.py

@@ -31,7 +31,7 @@ def get_long_description():
 
 install_requires = [
     "pyface",
-    "traits",
+    "traits>=6.2.0",
 ]
 
 

traits_futures/asyncio/event_loop_helper.py

@@ -96,11 +96,11 @@ def stop_on_timeout():
             timed_out.append(True)
             event_loop.stop()
 
-        def stop_if_condition():
+        def stop_if_condition(event):
             if condition(object):
                 event_loop.stop()
 
-        object.on_trait_change(stop_if_condition, trait)
+        object.observe(stop_if_condition, trait)
         try:
             # The condition may have become True before we
             # started listening to changes. So start with a check.
@@ -111,7 +111,7 @@ def stop_if_condition():
                 finally:
                     timer_handle.cancel()
         finally:
-            object.on_trait_change(stop_if_condition, trait, remove=True)
+            object.observe(stop_if_condition, trait, remove=True)
 
         if timed_out:
             raise RuntimeError(

traits_futures/qt/event_loop_helper.py

@@ -124,11 +124,11 @@ def run_until(self, object, trait, condition, timeout):
         def stop_on_timeout():
             qt_app.exit(1)
 
-        def stop_if_condition():
+        def stop_if_condition(event):
             if condition(object):
                 qt_app.exit(0)
 
-        object.on_trait_change(stop_if_condition, trait)
+        object.observe(stop_if_condition, trait)
         try:
             # The condition may have become True before we
             # started listening to changes. So start with a check.
@@ -143,7 +143,7 @@ def stop_if_condition():
                     timeout_timer.stop()
                     timeout_timer.timeout.disconnect(stop_on_timeout)
         finally:
-            object.on_trait_change(stop_if_condition, trait, remove=True)
+            object.observe(stop_if_condition, trait, remove=True)
 
         if timed_out:
             raise RuntimeError(

traits_futures/tests/common_future_tests.py

@@ -57,17 +57,17 @@ def test_cancellable_and_done_consistent_with_state(self):
         # Triples (state, cancellable, done)
         states = []
 
-        def record_states():
+        def record_states(event=None):
             """Record the future's state and derived traits."""
             states.append((future.state, future.cancellable, future.done))
 
         # Record state when any of the three traits changes.
         future = self.future_class()
         future._executor_initialized(dummy_cancel_callback)
 
-        future.on_trait_change(record_states, "cancellable")
-        future.on_trait_change(record_states, "done")
-        future.on_trait_change(record_states, "state")
+        future.observe(record_states, "cancellable")
+        future.observe(record_states, "done")
+        future.observe(record_states, "state")
 
         # Record initial, synthesize some state changes, then record final.
         record_states()

traits_futures/tests/traits_executor_tests.py

@@ -250,8 +250,8 @@ def test_submit_iteration_method(self):
             )
 
         results = []
-        future.on_trait_change(
-            lambda result: results.append(result), "result_event"
+        future.observe(
+            lambda event: results.append(event.new), "result_event"
         )
 
         self.wait_until_done(future)
@@ -295,7 +295,7 @@ def test_states_consistent(self):
         # Triples (state, running, stopped).
         states = []
 
-        def record_states():
+        def record_states(event=None):
             states.append(
                 (
                     self.executor.state,
@@ -304,9 +304,9 @@ def record_states():
                 )
             )
 
-        self.executor.on_trait_change(record_states, "running")
-        self.executor.on_trait_change(record_states, "stopped")
-        self.executor.on_trait_change(record_states, "state")
+        self.executor.observe(record_states, "running")
+        self.executor.observe(record_states, "stopped")
+        self.executor.observe(record_states, "state")
         submit_call(self.executor, int)
 
         # Record states before, during, and after stopping.

traits_futures/wx/event_loop_helper.py

@@ -212,11 +212,11 @@ def run_until(self, object, trait, condition, timeout):
 
         timeout_timer = TimeoutTimer(timeout, lambda: wx_app.exit(1))
 
-        def stop_if_condition():
+        def stop_if_condition(event):
             if condition(object):
                 wx_app.exit(0)
 
-        object.on_trait_change(stop_if_condition, trait)
+        object.observe(stop_if_condition, trait)
         try:
             # The condition may have become True before we
             # started listening to changes. So start with a check.
@@ -230,7 +230,7 @@ def stop_if_condition():
                     timed_out = wx_app.exit_code
                     timeout_timer.stop()
         finally:
-            object.on_trait_change(stop_if_condition, trait, remove=True)
+            object.observe(stop_if_condition, trait, remove=True)
 
         if timed_out:
             raise RuntimeError(