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core.py
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core.py
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"""Write ipywidgets like React
ReactJS - ipywidgets relation:
* DOM nodes -- Widget
* Element -- Element
* Component -- function
"""
import contextlib
import copy
import functools
import inspect
import logging
import sys
import threading
import traceback
import weakref
from collections import defaultdict
from dataclasses import dataclass, field
from inspect import isclass
from types import TracebackType
from typing import (
Any,
Callable,
ContextManager,
Dict,
Generic,
List,
Optional,
Set,
Tuple,
Type,
TypeVar,
Union,
cast,
overload,
)
from warnings import warn
import ipywidgets
import ipywidgets as widgets
import traitlets
import typing_extensions
from typing_extensions import Literal, Protocol
import reacton.logging # noqa: F401 # has sidefx
import reacton.patch_display # noqa: F401 # has sidefx
from . import _version, patch, utils # noqa: F401
__version__ = _version.__version__
ipywidget_version_major = int(widgets.__version__.split(".")[0])
# see solara/server/patch.py for similar code
def _widgets_dict_getter() -> Callable[[], Dict[str, widgets.Widget]]:
if ipywidget_version_major < 8:
def get():
return ipywidgets.widget.Widget.widgets
else:
if hasattr(ipywidgets.widgets.widget, "_instances"): # since 8.0.3
def get():
return ipywidgets.widgets.widget._instances
elif hasattr(ipywidgets.widget.Widget, "_instances"):
def get():
return ipywidgets.widget.Widget._instances
else:
raise RuntimeError("Could not find _instances on ipywidgets version %r" % ipywidgets.__version__)
return get
_get_widgets_dict = _widgets_dict_getter()
_last_rc = None # used for testing
local = threading.local()
T = TypeVar("T")
U = TypeVar("U")
W = TypeVar("W") # used for widgets
V = TypeVar("V") # used for value type of widget
V2 = TypeVar("V2") # used for value type of widget
E = TypeVar("E") # used for elements
P = typing_extensions.ParamSpec("P")
WidgetOrList = Union[widgets.Widget, List[widgets.Widget]]
EffectCleanupCallable = Callable[[], None]
EffectCallable = Callable[[], Optional[EffectCleanupCallable]]
ROOT_KEY = "ROOT::"
logger = logging.getLogger("reacton") # type: ignore
# this will show friendly stack traces
DEBUG = 0
# if True, will show the original stacktrace as cause
TRACEBACK_ORIGINAL = True
MIME_WIDGETS = "application/vnd.jupyter.widget-view+json"
widget_render_error_msg = (
"""Cannot show widget. You probably want to rerun the code cell above (<i>Click in the code cell, and press Shift+Enter <kbd>⇧</kbd>+<kbd>↩</kbd></i>)."""
)
mime_bundle_default = {"text/plain": "Cannot show ipywidgets in text", "text/html": widget_render_error_msg}
def element(cls, **kwargs):
return ComponentWidget(cls)(**kwargs)
def are_events_supressed():
return getattr(local, "events_supressed", False)
@contextlib.contextmanager
def suppress_events():
"""Suppress events while updating a widget"""
local.events_supressed = True
try:
yield
finally:
local.events_supressed = False
widgets.Widget.element = classmethod(element)
def close_widget(widget: widgets.Widget):
# this happens for v.Chip, which has a close trait
if callable(widget.close):
widget.close()
else:
logger.warning("Widget %r does not have a close method, possibly a close trait was added", widget)
def _event_handler_exception_wrapper(f):
"""Wrap an event handler to catch exceptions and put them in a reacton context.
This allows a component to catch the exception of a direct child"""
rc = get_render_context()
context = rc.context
assert context is not None
def wrapper(*args, **kwargs):
try:
f(*args, **kwargs)
except Exception as e:
assert context is not None
# because widgets don't have a context, but are a child of a component
# we add it to exceptions_children, not exception_self
# this allows a component to catch the exception of a direct child
context.exceptions_children.append(e)
rc.force_update()
return wrapper
def join_key(parent_key, key):
return f"{parent_key}{key}"
def pp(o):
import prettyprinter
prettyprinter.install_extras()
prettyprinter.pprint(o, width=200)
def same_component(c1, c2):
# return (c1.f.__name__ == c2.f.__name__) and (c1.f.__module__ == c2.f.__module__)
return c1 == c2
def _with_tracebacks(e, tracebacks):
# copy it, and we need with_traceback for unknown reasons not to cause
# an infinite loop
e_original = e
e = copy.copy(e).with_traceback(e.__traceback__)
tb_next = None
# last item is the top of the stack
for tb in tracebacks:
# make a copy, so we do not mutate the original traceback
tb = TracebackType(tb_next=tb_next, tb_frame=tb.tb_frame, tb_lasti=tb.tb_lasti, tb_lineno=tb.tb_lineno)
tb_next = tb
if TRACEBACK_ORIGINAL:
e = e.with_traceback(tb_next)
e_original.__cause__ = e
return e_original
else:
e = e.with_traceback(tb_next)
return e
class ComponentCreateError(RuntimeError):
def __init__(self, rich_traceback):
super().__init__(rich_traceback)
self.rich_traceback = rich_traceback
class Component:
name: str
def __call__(self, *args, **kwargs) -> Union[widgets.Widget, "Element"]:
pass
class Element(Generic[W]):
child_prop_name = "children"
# to make every unique on_value callback to a unique wrapper
# so that we can remove the listeners
_callback_wrappers: Dict[Tuple[str, str, Callable], Callable] = {}
create_lock: ContextManager = threading.Lock()
_shared = False
def __init__(self, component, args=None, kwargs=None):
self.component = component
self.mime_bundle = mime_bundle_default
self._key: Optional[str] = None
self.args = args or []
self.kwargs = kwargs or {}
self.handlers = []
self._meta = {}
# for debugging/testing only
self._render_count = 0
self._key_frozen: bool = False
rc = _get_render_context(required=False)
if rc is not None and rc.container_adders:
rc.container_adders[-1].add(self)
if DEBUG:
# since we construct widgets or components from a different code path
# we want to preserve the original call stack, by manually tracking frames
try:
assert False
except AssertionError:
self.traceback = cast(TracebackType, sys.exc_info()[2])
assert self.traceback is not None
assert self.traceback.tb_frame is not None
assert self.traceback.tb_frame.f_back is not None
frame_py = self.traceback.tb_frame.f_back.f_back
assert frame_py is not None
self.traceback = TracebackType(tb_frame=frame_py, tb_lasti=self.traceback.tb_lasti, tb_lineno=frame_py.f_lineno, tb_next=None)
def _arguments_changed(self, other: "Element"):
if len(self.args) != len(other.args):
return True
if len(self.kwargs) != len(other.kwargs):
return True
for k, v in self.kwargs.items():
if k not in other.kwargs:
return True
if not utils.equals(v, other.kwargs[k]):
return True
for a, b in zip(self.args, other.args):
if not utils.equals(a, b):
return True
return False
def key(self, value: str):
"""Returns the same element with a custom key set.
This can help render performance. See documentation for details.
"""
if self._key_frozen:
raise RuntimeError("Element keys should not be mutated after rendering")
self._key = value
return self
def meta(self, **kwargs):
"""Add metadata to the created widget.
This can be used to find a widget for testing.
"""
self._meta = {**self._meta, **kwargs}
return self
@property
def is_shared(self):
return self._shared
def shared(self):
self._shared = True
return self
def __repr__(self):
def format_arg(value):
value_repr = repr(value)
if len(value_repr) > 50:
value_repr = value_repr[:10] + "..." + value_repr[-10:]
return value_repr
args = [format_arg(value) for value in self.args]
def format_kwarg(key, value):
if key == "children":
if isinstance(value, (list, tuple)) and len(value) > 0:
contains_elements = any(isinstance(child, Element) for child in value)
if contains_elements:
return "children = ..."
return f"{key} = {format_arg(value)}"
kwargs = [format_kwarg(key, value) for key, value in self.kwargs.items()]
args_formatted = ", ".join(args + kwargs)
if isinstance(self.component, ComponentFunction):
name = self.component.f.__name__
return f"{name}({args_formatted})"
if isinstance(self.component, ComponentWidget):
modulename = self.component.widget.__module__
# lets shorten e.g. ipyvuetify.generated.Label.Label to ipyvuetify.Label
shorten = "ipywidgets ipyvuetify ipyvue".split()
for prefix in shorten:
if modulename.startswith(prefix):
modulename = prefix
# don't replace ipyvuetify with ipyvue
break
name = modulename + "." + self.component.widget.__name__
return f"{name}({args_formatted})"
else:
raise RuntimeError(f"No repr for {type(self)}")
def on(self, name, callback):
self.handlers.append((name, callback))
return self
def _ipython_display_(self, **kwargs):
display(self, self.mime_bundle)
def __enter__(self):
rc = _get_render_context()
ca = ContainerAdder[T](self, "children")
assert rc.context is not None
rc.container_adders.append(ca)
return self
def __exit__(self, *args, **kwargs):
rc = _get_render_context()
assert rc.context is not None
ca = rc.container_adders.pop()
collected = ca.collect()
self.add_children(collected)
def add_children(self, children):
if self.child_prop_name not in self.kwargs:
self.kwargs[self.child_prop_name] = []
# generic way to add to a list or tuple
container_prop_type = type(self.kwargs[self.child_prop_name])
self.kwargs[self.child_prop_name] = self.kwargs[self.child_prop_name] + container_prop_type(children)
def _get_widget_args(self):
return self.component.widget.class_trait_names()
def _split_kwargs(self, kwargs):
# split into normal kwargs and events
listeners = {}
normal_kwargs = {}
assert isinstance(self.component, ComponentWidget)
args = self._get_widget_args()
for name, value in kwargs.items():
if name.startswith("on_") and name not in args:
listeners[name] = value
else:
normal_kwargs[name] = value
return normal_kwargs, listeners
def _close_widget(self, widget: widgets.Widget):
close_widget(widget)
try:
delattr(widget, "hold_trait_notifications")
except AttributeError:
raise
def _create_widget(self, kwargs):
# we can't use our own kwarg, since that contains elements, not widgets
kwargs, listeners = self._split_kwargs(kwargs)
assert isinstance(self.component, ComponentWidget)
# Because we look before and after, we need a lock.
# A different implementation might avoid this.
with self.create_lock:
rc = get_render_context(required=True)
before = set(_get_widgets_dict())
try:
widget = self.component.widget(**kwargs)
hold_trait_notifications = widget.hold_trait_notifications
@contextlib.contextmanager
def hold_trait_notifications_extra(*args, **kwargs):
with rc, hold_trait_notifications(*args, **kwargs):
yield
widget.hold_trait_notifications = hold_trait_notifications_extra
if self._meta:
widget._react_meta = dict(self._meta)
except Exception as e:
raise RuntimeError(f"Could not create widget {self.component.widget} with {kwargs}") from e
for name, callback in listeners.items():
if callback is not None:
self._add_widget_event_listener(widget, name, callback)
after = set(_get_widgets_dict())
orphans = (after - before) - {widget.model_id}
return widget, orphans
def _update_widget(self, widget: widgets.Widget, el_prev: "Element", kwargs):
assert isinstance(self.component, ComponentWidget)
assert isinstance(el_prev.component, ComponentWidget)
assert same_component(self.component, el_prev.component)
# used_kwargs, _ = el_prev.split_kwargs(el_prev.kwargs)
args = self.component.widget.class_trait_names()
with widget.hold_sync(), suppress_events():
# update values
for name, value in kwargs.items():
if name.startswith("on_") and name not in args:
self._update_widget_event_listener(widget, name, value, el_prev.kwargs.get(name))
else:
self._update_widget_prop(widget, name, value)
# if we previously gave an argument, but now we don't
# we have to restore the default values, and remove listeners
cls = widget.__class__
traits = cls.class_traits()
dropped_arguments = set(el_prev.kwargs) - set(self.kwargs)
for name in dropped_arguments:
if name.startswith("on_") and name not in args:
self._remove_widget_event_listener(widget, name, el_prev.kwargs[name])
else:
value = traits[name].default()
self._update_widget_prop(widget, name, value)
def _update_widget_prop(self, widget, name, value):
setattr(widget, name, value)
def _update_widget_event_listener(self, widget: widgets.Widget, name: str, callback: Optional[Callable], callback_prev: Optional[Callable]):
# it's an event listener
if callback != callback_prev and callback_prev is not None:
self._remove_widget_event_listener(widget, name, callback_prev)
if callback is not None and callback != callback_prev:
self._add_widget_event_listener(widget, name, callback)
def _add_widget_event_listener(self, widget: widgets.Widget, name: str, callback: Callable):
target_name = name[3:]
callback_exception_safe = _event_handler_exception_wrapper(callback)
def on_change(change):
if are_events_supressed():
return
logger.info("event %r on %r with %r", name, widget, change)
callback_exception_safe(change["new"])
key = (widget.model_id, name, callback)
self._callback_wrappers[key] = on_change
widget.observe(on_change, target_name)
def _remove_widget_event_listener(self, widget: widgets.Widget, name: str, callback: Callable):
target_name = name[3:]
key = (widget.model_id, name, callback)
on_change = self._callback_wrappers[key]
del self._callback_wrappers[key]
try:
widget.unobserve(on_change, target_name)
except ValueError:
logger.error("Could not remove event listener %r from %r", name, widget)
def _cleanup_callbacks(self, widget: widgets.Widget):
args = self._get_widget_args()
for name, value in self.kwargs.items():
if name.startswith("on_") and name not in args and value is not None:
self._remove_widget_event_listener(widget, name, value)
class Value(Generic[V], Protocol):
def get(self) -> V:
...
def set(self, value: V):
...
class ValueElement(Generic[W, V], Element[W]):
def __init__(self, value_property, component, args=None, kwargs=None):
self.value_property = value_property
super().__init__(component, args, kwargs)
# TODO: we want to enable something like this, but requires a good hash function
# for the key
# def use_value(self, *default) -> V:
# assert self.value_property in self.kwargs
# default_value = self.kwargs[self.value_property]
# # if not default:
# # else:
# # default_value = default[0]
# # if "kwargs" in self.kwargs:
# # default_value = self.kwargs["value"]
# value, set_value = use_state(default_value)
# self.kwargs[self.value_property] = value
# self.kwargs[f"on_{self.value_property}"] = lambda x: set_value(x)
# return value
def connect(self, value: Value[V]):
"""Will automatically set up a connection between the value and the widget.
The object passed should have a get and set method. The get method
set the current value, while the set method will be called when the
`on_value` event is triggered.
The get method could also be used to automically set up listeners.
"""
self.kwargs[self.value_property] = value.get()
self.kwargs[f"on_{self.value_property}"] = lambda x: value.set(x)
return self
FuncT = TypeVar("FuncT", bound=Callable[..., Element])
def find_elements(value: Union[Element, List, Tuple, Dict]) -> Set[Element]:
if isinstance(value, Element):
el = value
elements = {el}
if not isinstance(el.kwargs, dict):
raise RuntimeError("keyword arguments for {el} should be a dict, not {el.kwargs}")
elements |= find_elements(el.args)
elements |= find_elements(el.kwargs)
return elements
elif isinstance(value, (tuple, list)):
elements = set()
for child in value:
if isinstance(child, (Element, tuple, list, dict)):
elements |= find_elements(child)
return elements
elif isinstance(value, dict):
elements = set()
for child in value.values():
if isinstance(child, (Element, tuple, list, dict)):
elements |= find_elements(child)
return elements
class ContainerAdder(Generic[W]):
def __init__(self, el: Element[W], prop_name: str):
self.el = el
self.prop_name = prop_name
self.created: List[Element] = []
def add(self, el):
self.created.append(el)
def collect(self):
children = set()
for el in self.created:
children |= find_elements(el) - {el}
top_level = [k for k in self.created if k not in children]
return top_level
class ComponentWidget(Component):
def __init__(self, widget: Type[widgets.Widget], mime_bundle=mime_bundle_default):
self.mime_bundle = mime_bundle
self.widget = widget
self.name = widget.__name__
def __eq__(self, rhs):
if self is rhs:
return True
if not isinstance(rhs, ComponentWidget):
return False
return self.widget == rhs.widget
def __repr__(self):
return f"Component[{self.widget!r}]"
def __call__(self, *args, **kwargs):
el: Element = Element(self, args=args, kwargs=kwargs)
# TODO: temporary, we cannot change the constructor
# otherwise we need to generate the wrapper code again for all libraries
el.mime_bundle = self.mime_bundle
return el
class ComponentFunction(Component):
def __init__(self, f: Callable[[], Element], mime_bundle=mime_bundle_default, value_name=None):
self.f = f
self.name = self.f.__name__
self.mime_bundle = mime_bundle
self.value_name = value_name
self.render_count = 0 # used for debugging, not thread safe, so count can be off
functools.update_wrapper(self, f)
def widget(self, **kwargs):
_ensure_colab_fixes()
return self.widget_class()(**kwargs)
def widget_class(self):
parameters = inspect.signature(self.f).parameters
args = list(parameters.keys())
listeners = set()
normal_kwargs = set()
for name in args:
if name.startswith("on_"):
listeners.add(name)
else:
normal_kwargs.add(name)
component = self
class Container(widgets.VBox, widgets.ValueWidget):
description = traitlets.Unicode()
def __init__(self, **kwargs):
super().__init__(**kwargs)
self._children = []
traits = {}
for name in normal_kwargs:
if name != "children": # children is a special trait we keep
if name in normal_kwargs:
trait = traitlets.Any(default_value=parameters[name].default)
else:
trait = traitlets.Any()
traits[name] = trait
Container.add_traits(self, **traits)
for name, value in kwargs.items():
if name in normal_kwargs:
setattr(self, name, value)
for name in normal_kwargs:
self.observe(self._rerender, name)
el = self._create_el()
self.rc = _RenderContext(el, self)
self.rc.render(el, self)
def _create_el(self):
kwargs = {}
for name in normal_kwargs:
if name != "children":
kwargs[name] = getattr(self, name)
for name in listeners:
propname = name[3:]
def closure(propname=propname):
def setter(value):
setattr(self, propname, value)
return setter
kwargs[name] = closure()
logger.info("calling component with kwargs: %r", kwargs)
return component(**kwargs)
def _rerender(self, change):
el = self._create_el()
self.rc.update(el)
return Container
def __eq__(self, rhs):
if self is rhs:
return True
if not isinstance(rhs, ComponentFunction):
return False
return self.f == rhs.f
def __repr__(self):
return f"react.component({self.f.__module__}.{self.f.__name__})"
def __call__(self, *args, **kwargs):
if self.value_name is not None:
el: Element = ValueElement(self.value_name, self, args=args, kwargs=kwargs)
else:
el = Element(self, args=args, kwargs=kwargs)
el.mime_bundle = self.mime_bundle
return el
@overload
def component(obj: None = None, mime_bundle=...) -> Callable[[FuncT], FuncT]:
...
@overload
def component(obj: FuncT, mime_bundle=...) -> FuncT:
...
@overload
def component(obj: Callable[P, None], mime_bundle=...) -> Callable[P, Element]:
...
# it is actually this...
# def component(obj: Union[Type[widgets.Widget], FuncT]) -> Union[ComponentWidget, ComponentFunction[FuncT]]:
# but casting to FuncT gives much better type hints (e.g. argument types checks etc)
def component(obj: Union[Callable[P, None], FuncT] = None, mime_bundle: Dict[str, Any] = mime_bundle_default):
def wrapper(obj: Union[Callable[P, None], FuncT]) -> FuncT:
if isclass(obj) and issubclass(obj, widgets.Widget):
return cast(FuncT, ComponentWidget(widget=obj, mime_bundle=mime_bundle))
else:
return cast(FuncT, ComponentFunction(f=cast(FuncT, obj), mime_bundle=mime_bundle))
if obj is not None:
return wrapper(obj)
else:
return wrapper
@overload
def value_component(
value_type: None, value_name="value", mime_bundle: Dict[str, Any] = mime_bundle_default
) -> Callable[[Callable[P, ValueElement[W, V]]], Callable[P, ValueElement[W, V]]]:
...
@overload
def value_component(
value_type: Type[V], value_name="value", mime_bundle: Dict[str, Any] = mime_bundle_default
) -> Callable[[Callable[P, Element[W]]], Callable[P, ValueElement[W, V]]]:
...
def value_component(value_type: Union[Type[V], None], value_name="value", mime_bundle: Dict[str, Any] = mime_bundle_default):
"""Creates a custom component that returns a ValueElement.
A ValueElement is a special element that can be used to connect to a Value, and be used to automatically
wire up the value and on_value events.
"""
def wrapper(obj: Callable[P, Union[Element[W], ValueElement[W, V2]]]) -> Callable[P, ValueElement[W, V]]:
if isclass(obj) and issubclass(obj, widgets.Widget):
return cast(Callable[P, ValueElement[T, V]], ComponentWidget(widget=obj, mime_bundle=mime_bundle))
else:
return cast(Callable[P, ValueElement[T, V]], ComponentFunction(f=obj, mime_bundle=mime_bundle, value_name=value_name))
return wrapper
def force_update():
rc = _get_render_context()
rc.force_update()
def get_widget(el: Element):
"""Returns the real underlying widget, can only be used in use_effect.
Note that if the same element it used twice in a component, the widget corresponding to the last
element will be returned.
"""
rc = get_render_context()
# breadth first search
contexts = [rc.context]
while contexts:
context = contexts.pop()
if context is None:
raise RuntimeError("get_widget() can only be used in use_effect")
contexts.extend(context.children.values())
if el.is_shared:
if el not in rc._shared_widgets:
return rc._shared_widgets[el]
else:
if el in context.element_to_widget:
return context.element_to_widget[el]
if id(el) in rc._old_element_ids:
raise KeyError(f"Element {el} was found to be in a previous render, you may have used a stale element")
raise KeyError(f"Element {el} not found in all known widgets") # for the component {context.widgets}")
def use_state(initial: T, key: str = None, eq: Callable[[Any, Any], bool] = None) -> Tuple[T, Callable[[Union[T, Callable[[T], T]]], None]]:
"""Returns a `(value, setter)` tuple that is used to manage state in a component.
This function can only be called from a component function.
The value returns the current state (which equals `initial` at the first render call). Or the value that was last set using the setter.
Note that the setter function can be used in two ways.
Directly setting the value:
```python
@reacton.component
def ButtonClick():
clicks, set_clicks = reacton.use_state(0)
def my_click_handler():
set_clicks(clicks+1)
button = w.Button(description=f"Clicked {clicks} times",
on_click=my_click_handler)
return button
```
Updating the value based on the previous/current value.
```python
@reacton.component
def ButtonClick():
clicks, set_clicks = reacton.use_state(0)
def my_click_handler():
set_clicks(lambda prev: prev+1)
button = w.Button(description=f"Clicked {clicks} times",
on_click=my_click_handler)
return button
```
The last one avoid issues with stale data, which means you have a reference to the value of an old render pass (not present in this simple example).
"""
rc = _get_render_context()
return rc.use_state(initial, key, eq)
def use_effect(effect: EffectCallable, dependencies=None):
rc = _get_render_context()
return rc.use_effect(effect, dependencies=dependencies)
def use_side_effect(effect: EffectCallable, dependencies=None):
warn("use_side_effect is deprecated, please use use_effect", DeprecationWarning, stacklevel=2)
return use_effect(effect=effect, dependencies=dependencies)
def use_state_widget(widget: widgets.Widget, prop_name, key=None):
rc = _get_render_context()
initial_value = getattr(widget, prop_name)
value, setter = use_state(initial_value, key=key)
if rc.first_render:
def handler(change):
setter(change.new) # type: ignore
widget.observe(handler, prop_name)
return value
@overload
def get_render_context(required: Literal[True] = ...) -> "_RenderContext":
...
@overload
def get_render_context(required: Literal[False] = ...) -> Optional["_RenderContext"]:
...
def get_render_context(required=True):
rc = getattr(local, "rc", None)
if rc is None and required:
raise RuntimeError("No render context")
return rc
# previous name
_get_render_context = get_render_context
def use_reducer(reduce: Callable[[T, U], T], initial_state: T) -> Tuple[T, Callable[[U], None]]:
state, set_state = use_state(initial_state)
def dispatch(action):
def state_updater(state):
return reduce(state, action)
set_state(state_updater)
return state, dispatch
def use_memo(f: Callable[[], T], dependencies=None, debug_name: str = None) -> T:
if debug_name is None:
debug_name = f.__name__
rc = _get_render_context()
if dependencies is None:
dependencies = inspect.getclosurevars(f).nonlocals
dependencies = {k: v for k, v in dependencies.items() if not k.startswith("__")}
return rc.use_memo(f, dependencies, debug_name)
else:
return rc.use_memo(f, dependencies, debug_name)
def use_callback(f, dependencies):
def wrapper(*ignore):
return f
use_memo(wrapper, dependencies)
def use_exception() -> Tuple[Optional[BaseException], Callable[[], None]]:
rc = _get_render_context(required=True)
assert rc.context is not None
# we keep track of the exception in the state because we want to explicitly
# clear it.
exception, set_exception = use_state(cast(Optional[BaseException], None))
rc.context.exception_handler = True
if rc.context.exceptions_children:
# if we found an exception in one of our children, we want to return this
# exception, until clear is called.
e = rc.context.exceptions_children[0]
# reset the exceptions that we found
rc.context.exceptions_children = []
set_exception(e)
exception = e
def clear():
set_exception(None)
logger.info("use_exception: %r", exception)
return exception, clear
class Ref(Generic[T]):
def __init__(self, initial_value: T):
self.current = initial_value
def use_ref(initial_value: T) -> Ref[T]:
def make_ref():
return Ref(initial_value)
ref = use_memo(make_ref, [])
return ref
class UserContext(Generic[T]):
def __init__(self, _default_value: T, name: Optional[str]) -> None:
self._default_value: T = _default_value
self.name = name
def provide(self, obj: T):
rc = _get_render_context()
context = rc.context
assert context is not None
prev = context.user_contexts_prev.get(self, self._default_value)
context.user_contexts[self] = obj
if not utils.equals(prev, obj):
for listener in context.context_listeners.get(self, []):
listener()
def get(self):
"""Convenience method to get the context value, same as get_context"""
return get_context(self)
def use(self):
"""Convenience method to use the context value, same as use_context"""
return use_context(self)
def __repr__(self):
return f"UserContext({self._default_value}, name={self.name})"
def create_context(default_value: T, name: str = None) -> UserContext[T]:
return UserContext[T](default_value, name)
# this does not work with well mypy, UserContext[T] and obj:T
# so for type hints it is better to use user_context.provide
def provide_context(user_context: UserContext[T], obj: T):
user_context.provide(obj)
def get_context(user_context: UserContext[T]) -> T:
"""Similar to use_context, but does not trigger a re-render if the context changes."""
rc = _get_render_context()
value = None
assert rc.context is not None
context = rc.context.parent
# we need to walk up the context tree to find the nearest
# ancestor that has the context we are looking for.
while value is None and context is not None:
if user_context in context.user_contexts:
value = context.user_contexts.get(user_context)
break
else:
context = context.parent
if context is None:
# we did not find the context, so we return the default value
return user_context._default_value
else:
return cast(T, value)
def use_context(user_context: UserContext[T]) -> T:
counter, set_counter = use_state(0)
def force_update():
set_counter(lambda x: x + 1)
rc = _get_render_context()
value = None
assert rc.context is not None
context = rc.context.parent
# we need to walk up the context tree to find the nearest
# ancestor that has the context we are looking for.
while value is None and context is not None:
if user_context in context.user_contexts: