Backport echo widget state to 7.x

This backports the combination of jupyter-widgets#3195 and jupyter-widgets#3394.

ipywidgets/_version.py

@@ -8,7 +8,7 @@
 __version__ = '%s.%s.%s%s'%(version_info[0], version_info[1], version_info[2],
  '' if version_info[3]=='final' else _specifier_[version_info[3]]+str(version_info[4]))
 
-__protocol_version__ = '2.0.0'
+__protocol_version__ = '2.1.0'
 __control_protocol_version__ = '1.0.0'
 
 # These are *protocol* versions for each package, *not* npm versions. To check, look at each package's src/version.ts file for the protocol version the package implements.

ipywidgets/widgets/tests/test_set_state.py

@@ -86,7 +86,7 @@ def test_set_state_simple():
  c=[False, True, False],
  ))
 
- assert w.comm.messages == []
+ assert len(w.comm.messages) == 1
 
 
 def test_set_state_transformer():
@@ -96,11 +96,18 @@ def test_set_state_transformer():
  ))
  # Since the deserialize step changes the state, this should send an update
  assert w.comm.messages == [((), dict(
+ buffers=[],
+ data=dict(
+ buffer_paths=[],
+ method='echo_update',
+ state=dict(d=[True, False, True]),
+ ))),
+ ((), dict(
  buffers=[],
  data=dict(
  buffer_paths=[],
  method='update',
- state=dict(d=[False, True, False])
+ state=dict(d=[False, True, False]),
  )))]
 
 
@@ -111,7 +118,7 @@ def test_set_state_data():
  a=True,
  d={'data': data},
  ))
- assert w.comm.messages == []
+ assert len(w.comm.messages) == 1
 
 
 def test_set_state_data_truncate():
@@ -122,15 +129,15 @@ def test_set_state_data_truncate():
  d={'data': data},
  ))
  # Get message for checking
- assert len(w.comm.messages) == 1 # ensure we didn't get more than expected
- msg = w.comm.messages[0]
+ assert len(w.comm.messages) == 2 # ensure we didn't get more than expected
+ msg = w.comm.messages[1]
  # Assert that the data update (truncation) sends an update
  buffers = msg[1].pop('buffers')
  assert msg == ((), dict(
  data=dict(
- buffer_paths=[['d', 'data']],
  method='update',
- state=dict(d={})
+ state=dict(d={}),
+ buffer_paths=[['d', 'data']]
  )))
 
  # Sanity:
@@ -150,8 +157,8 @@ def test_set_state_numbers_int():
  i = 3,
  ci = 4,
  ))
- # Ensure no update message gets produced
- assert len(w.comm.messages) == 0
+ # Ensure one update message gets produced
+ assert len(w.comm.messages) == 1
 
 
 def test_set_state_numbers_float():
@@ -162,8 +169,8 @@ def test_set_state_numbers_float():
  cf = 2.0,
  ci = 4.0
  ))
- # Ensure no update message gets produced
- assert len(w.comm.messages) == 0
+ # Ensure one update message gets produced
+ assert len(w.comm.messages) == 1
 
 
 def test_set_state_float_to_float():
@@ -173,8 +180,8 @@ def test_set_state_float_to_float():
  f = 1.2,
  cf = 2.6,
  ))
- # Ensure no update message gets produced
- assert len(w.comm.messages) == 0
+ # Ensure one message gets produced
+ assert len(w.comm.messages) == 1
 
 
 def test_set_state_cint_to_float():
@@ -185,8 +192,8 @@ def test_set_state_cint_to_float():
  ci = 5.6
  ))
  # Ensure an update message gets produced
- assert len(w.comm.messages) == 1
- msg = w.comm.messages[0]
+ assert len(w.comm.messages) == 2
+ msg = w.comm.messages[1]
  data = msg[1]['data']
  assert data['method'] == 'update'
  assert data['state'] == {'ci': 5}
@@ -241,13 +248,135 @@ def _propagate_value(self, change):
  # this mimics a value coming from the front end
  widget.set_state({'value': 42})
  assert widget.value == 42
+ assert widget.stop is True
+
+ # we expect no new state to be sent
+ calls = []
+ widget._send.assert_has_calls(calls)
+
+
+def test_hold_sync():
+ # when this widget's value is set to 42, it sets the value to 2, and also sets a different trait value
+ class AnnoyingWidget(Widget):
+ value = Float().tag(sync=True)
+ other = Float().tag(sync=True)
+
+ @observe('value')
+ def _propagate_value(self, change):
+ print('_propagate_value', change.new)
+ if change.new == 42:
+ self.value = 2
+ self.other = 11
 
- # we expect first the {'value': 2.0} state to be send, followed by the {'value': 42.0} state
- msg = {'method': 'update', 'state': {'value': 2.0}, 'buffer_paths': []}
+ widget = AnnoyingWidget(value=1)
+ assert widget.value == 1
+
+ widget._send = mock.MagicMock()
+ # this mimics a value coming from the front end
+ widget.set_state({'value': 42})
+ assert widget.value == 2
+ assert widget.other == 11
+
+ msg = {'method': 'echo_update', 'state': {'value': 42.0}, 'buffer_paths': []}
+ call42 = mock.call(msg, buffers=[])
+
+ msg = {'method': 'update', 'state': {'value': 2.0, 'other': 11.0}, 'buffer_paths': []}
  call2 = mock.call(msg, buffers=[])
 
- msg = {'method': 'update', 'state': {'value': 42.0}, 'buffer_paths': []}
+ calls = [call42, call2]
+ widget._send.assert_has_calls(calls)
+
+
+def test_echo():
+ # we always echo values back to the frontend
+ class ValueWidget(Widget):
+ value = Float().tag(sync=True)
+
+ widget = ValueWidget(value=1)
+ assert widget.value == 1
+
+ widget._send = mock.MagicMock()
+ # this mimics a value coming from the front end
+ widget.set_state({'value': 42})
+ assert widget.value == 42
+
+ # we expect this to be echoed
+ msg = {'method': 'echo_update', 'state': {'value': 42.0}, 'buffer_paths': []}
  call42 = mock.call(msg, buffers=[])
 
- calls = [call2, call42]
+ calls = [call42]
  widget._send.assert_has_calls(calls)
+
+
+
+def test_echo_single():
+ # we always echo multiple changes back in 1 update
+ class ValueWidget(Widget):
+ value = Float().tag(sync=True)
+ square = Float().tag(sync=True)
+ @observe('value')
+ def _square(self, change):
+ self.square = self.value**2
+
+ widget = ValueWidget(value=1)
+ assert widget.value == 1
+
+ widget._send = mock.MagicMock()
+ # this mimics a value coming from the front end
+ widget._handle_msg({
+ 'content': {
+ 'data': {
+ 'method': 'update',
+ 'state': {
+ 'value': 8,
+ }
+ }
+ }
+ })
+ assert widget.value == 8
+ assert widget.square == 64
+
+ # we expect this to be echoed
+ # note that only value is echoed, not square
+ msg = {'method': 'echo_update', 'state': {'value': 8.0}, 'buffer_paths': []}
+ call = mock.call(msg, buffers=[])
+
+ msg = {'method': 'update', 'state': {'square': 64}, 'buffer_paths': []}
+ call2 = mock.call(msg, buffers=[])
+
+
+ calls = [call, call2]
+ widget._send.assert_has_calls(calls)
+
+
+def test_no_echo():
+ # in cases where values coming from the frontend are 'heavy', we might want to opt out
+ class ValueWidget(Widget):
+ value = Float().tag(sync=True, echo_update=False)
+
+ widget = ValueWidget(value=1)
+ assert widget.value == 1
+
+ widget._send = mock.MagicMock()
+ # this mimics a value coming from the front end
+ widget._handle_msg({
+ 'content': {
+ 'data': {
+ 'method': 'update',
+ 'state': {
+ 'value': 42,
+ }
+ }
+ }
+ })
+ assert widget.value == 42
+
+ # widget._send.assert_not_called(calls)
+ widget._send.assert_not_called()
+
+ # a regular set should sync to the frontend
+ widget.value = 43
+ widget._send.assert_has_calls([mock.call({'method': 'update', 'state': {'value': 43.0}, 'buffer_paths': []}, buffers=[])])
+
+
+

ipywidgets/widgets/widget.py

@@ -7,6 +7,7 @@
 in the IPython notebook front-end.
 """
 
+import os
 from contextlib import contextmanager
 try:
  from collections.abc import Iterable
@@ -26,8 +27,26 @@
 from base64 import standard_b64encode
 
 from .._version import __protocol_version__, __control_protocol_version__, __jupyter_widgets_base_version__
+
+
+# Based on jupyter_core.paths.envset
+def envset(name, default):
+ """Return True if the given environment variable is turned on, otherwise False
+ If the environment variable is set, True will be returned if it is assigned to a value
+ other than 'no', 'n', 'false', 'off', '0', or '0.0' (case insensitive).
+ If the environment variable is not set, the default value is returned.
+ """
+ if name in os.environ:
+ return os.environ[name].lower() not in ['no', 'n', 'false', 'off', '0', '0.0']
+ else:
+ return bool(default)
+
+
+
+
 PROTOCOL_VERSION_MAJOR = __protocol_version__.split('.')[0]
 CONTROL_PROTOCOL_VERSION_MAJOR = __control_protocol_version__.split('.')[0]
+JUPYTER_WIDGETS_ECHO = envset('JUPYTER_WIDGETS_ECHO', default=True)
 
 def _widget_to_json(x, obj):
  if isinstance(x, dict):
@@ -580,6 +599,21 @@ def _compare(self, a, b):
 
  def set_state(self, sync_data):
  """Called when a state is received from the front-end."""
+ # Send an echo update message immediately
+ if JUPYTER_WIDGETS_ECHO:
+ echo_state = {}
+ for attr,value in sync_data.items():
+ if self.trait_metadata(attr, 'echo_update', default=True):
+ echo_state[attr] = value
+ if echo_state:
+ echo_state, echo_buffer_paths, echo_buffers = _remove_buffers(echo_state)
+ msg = {
+ 'method': 'echo_update',
+ 'state': echo_state,
+ 'buffer_paths': echo_buffer_paths,
+ }
+ self._send(msg, buffers=echo_buffers)
+
  # The order of these context managers is important. Properties must
  # be locked when the hold_trait_notification context manager is
  # released and notifications are fired.

ipywidgets/widgets/widget_upload.py

@@ -45,7 +45,7 @@ class FileUpload(DescriptionWidget, ValueWidget, CoreWidget):
  style = InstanceDict(ButtonStyle).tag(sync=True, **widget_serialization)
  metadata = List(Dict(), help='List of file metadata').tag(sync=True)
  data = List(Bytes(), help='List of file content (bytes)').tag(
- sync=True, from_json=content_from_json
+ sync=True, echo_update=False, from_json=content_from_json
  )
  error = Unicode(help='Error message').tag(sync=True)
  value = Dict(read_only=True)