Ensure refs can be updated by watcher of the same parameter (#929)

param/parameterized.py

@@ -1471,12 +1471,13 @@ def __set__(self, obj, val):
  item in a list).
  """
  name = self.name
- if obj is not None and self.allow_refs and obj._param__private.initialized and name not in obj._param__private.syncing:
+ if obj is not None and self.allow_refs and obj._param__private.initialized:
+ syncing = name in obj._param__private.syncing
  ref, deps, val, is_async = obj.param._resolve_ref(self, val)
  refs = obj._param__private.refs
  if ref is not None:
  self.owner.param._update_ref(name, ref)
- elif name in refs:
+ elif name in refs and not syncing:
  del refs[name]
  if name in obj._param__private.async_refs:
  obj._param__private.async_refs.pop(name).cancel()

tests/testreactive.py

@@ -709,3 +709,35 @@ def debug(value, info):
  arx.rx.value = 'd'
  assert expr.rx.value == 'DC'
  assert computed == ['1', '2', '2', '1']
+
+
+def test_ensure_ref_can_update_by_watcher_of_same_parameter():
+ # https://github.com/holoviz/param/pull/929
+
+ class W(param.Parameterized):
+ value = param.String()
+
+
+ class T(param.Parameterized):
+ lst = param.List(allow_refs=True, allow_None=True)
+
+ @param.depends("lst", watch=True)
+ def test(self):
+ lst = self.lst or range(5)
+ items = [W(value=str(i)) for i in lst]
+ with param.discard_events(self):
+ self.lst = param.rx(items).rx.resolve()
+ self.items = items
+
+ def transform(obj):
+ if isinstance(obj, W):
+ return obj.param.value
+ return obj
+
+
+ param.reactive.register_reference_transform(transform)
+
+ t = T()
+ t.lst = list("ABCDE")
+ t.items[1].value = "TEST"
+ assert t.lst[1] == "TEST"