Replace declare with reacttrs (#30)

Author: davidbrochart

README.md

@@ -5,6 +5,6 @@
 `ypywidgets` is a communication backend between a Jupyter kernel and clients. It allows to synchronize data structures that can be modified concurrently, and automatically resolves conflicts. To do so, it uses:
 - the Jupyter kernel [Comm](https://jupyter-client.readthedocs.io/en/stable/messaging.html#custom-messages) protocol as the transport layer, and the [comm](https://github.com/ipython/comm) implementation of it.
 - the [pycrdt](https://github.com/davidbrochart/pycrdt) CRDT implementation.
-- the [declare](https://github.com/willmcgugan/declare) library that implements the observer pattern and validation.
+- the [reacttrs](https://github.com/davidbrochart/reacttrs) library that implements the observer pattern and validation.
 
 It is a replacement for (a part of) [ipywidgets](https://ipywidgets.readthedocs.io). When used with [yjs-widgets](https://github.com/davidbrochart/yjs-widgets), it supports JupyterLab clients that implement widgets. The difference with `ipywidgets` is that these widgets are collaborative: they can be manipulated concurrently from the kernel or from any client. The CRDT algorithm ensures that a widget state will eventually be consistent across all clients.

pyproject.toml

@@ -20,7 +20,7 @@ keywords = [
 dependencies = [
     "comm >=0.1.4,<1",
     "pycrdt >=0.8.30,<0.9.0",
-    "declare >=1.0.1,<2.0.0",
+    "reacttrs >=0.2.1,<0.3.0",
 ]
 
 [project.urls]

tests/test_attributes.py

@@ -3,18 +3,18 @@
 
 import pytest
 from pycrdt import Text
-from ypywidgets import Declare
+from ypywidgets import Reactive
 from ypywidgets.comm import CommWidget
 
 
 class Widget1(CommWidget):
-    foo = Declare[str]("foo1")
-    bar = Declare[str]("bar1")
-    baz = Declare[Optional[str]](None)
+    foo = Reactive[str]("foo1")
+    bar = Reactive[str]("bar1")
+    baz = Reactive[Optional[str]](None)
 
 
 class Widget2(CommWidget):
-    foo = Declare[str]("")
+    foo = Reactive[str]("")
 
     @foo.watch
     def _watch_foo(self, old, new):

ypywidgets/__init__.py

@@ -1,5 +1,5 @@
 from .widget import Widget as Widget
-from .declare import Declare as Declare
+from .reactive import Reactive as Reactive
 
 
 __version__ = "0.8.1"

ypywidgets/declare.py

@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from typing import Generic
+
+from pycrdt import ReadTransaction
+from reacttrs import Reactive as _Reactive
+from reacttrs.reactive import Validator, ValueType, Watcher
+
+from .widget import Widget
+
+
+class Reactive(_Reactive, Generic[ValueType]):
+
+    def __init__(
+        self,
+        default: ValueType,
+        *,
+        validate: Validator | None = None,
+        watchers: set[Watcher] | None = None,
+    ) -> None:
+        super().__init__(default, validate=validate, watchers=watchers)
+
+        @self.watch
+        def _set_attr(obj: Widget, old: ValueType, new: ValueType) -> None:
+            with obj.ydoc.transaction() as txn:
+                # if we set the attribute, we are observing our own change: do nothing
+                # we know it's the case because callbacks provide read-only transactions
+                if not isinstance(txn, ReadTransaction):
+                    obj._attrs[self._name] = new