Support for Extended Tasks (#907)

Author: jcheng5

CHANGELOG.md

@@ -14,12 +14,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### New features
 
+* Added `shiny.ui.input_task_button()` for creating buttons that launch longer-running tasks than `shiny.ui.input_action_button()` was designed for. Task buttons give visual feedback that the task is running, and cannot be clicked again until the task is complete. (#907)
+
+* Added `@extended_task` decorator for creating long-running tasks that can be cancelled. (#907)
+
 * Added `@render.download` as a replacement for `@session.download`, which is now deprecated. (#977)
 
 * Added `ui.output_code()`, which is currently an alias for `ui.output_text_verbatim()`. (#997)
 
 * Added `@render.code`, which is an alias for `@render.text`, but in Express mode, it displays the result using `ui.output_code()`. (#997)
 
+* Added `App.on_shutdown` method for registering a callback to be called when the app is shutting down. (#907)
+
 ### Bug fixes
 
 * CLI command `shiny create`... (#965)

js/build.ts

@@ -61,6 +61,11 @@ const opts: Array<BuildOptions> = [
     minify: false,
     sourcemap: false,
   },
+  {
+    entryPoints: { "spin/spin": "spin/spin.scss" },
+    plugins: [sassPlugin({ type: "css", sourceMap: false })],
+    metafile: true,
+  },
 ];
 
 // Run function to avoid top level await

js/spin/spin.scss

@@ -0,0 +1,14 @@
+@keyframes py-shiny-spin {
+  0% {
+    transform: rotate(0deg);
+  }
+  100% {
+    transform: rotate(360deg);
+  }
+}
+
+@media (prefers-reduced-motion: no-preference) {
+  .py-shiny-spin {
+    animation: py-shiny-spin 2s linear infinite;
+  }
+}

scripts/htmlDependencies.R

@@ -11,7 +11,7 @@ versions <- list()
 message("Installing GitHub packages: bslib, shiny, htmltools")
 withr::local_temp_libpaths()
 ignore <- capture.output({
-  pak::pkg_install(c("rstudio/bslib", "cran::shiny", "cran::htmltools"))
+  pak::pkg_install(c("rstudio/bslib@v0.6.1-plus-layout-columns-and-task-button", "rstudio/shiny@main", "cran::htmltools"))
   #pak::pkg_install(c("rstudio/bslib@main", "rstudio/shiny@main", "rstudio/htmltools@main"))
 })
 

setup.cfg

@@ -132,6 +132,7 @@ profile=black
 skip=
     __init__.py
     typings/
+    _dev/
     .venv
     venv
     .tox

shiny/_app.py

@@ -3,9 +3,10 @@
 import copy
 import os
 import secrets
+from contextlib import AsyncExitStack, asynccontextmanager
 from inspect import signature
 from pathlib import Path
-from typing import Any, Callable, Optional, cast
+from typing import Any, Callable, Optional, TypeVar, cast
 
 import starlette.applications
 import starlette.exceptions
@@ -33,6 +34,8 @@
 from .http_staticfiles import FileResponse, StaticFiles
 from .session import Inputs, Outputs, Session, session_context
 
+T = TypeVar("T")
+
 # Default values for App options.
 LIB_PREFIX: str = "lib/"
 SANITIZE_ERRORS: bool = False
@@ -109,6 +112,10 @@ def __init__(
         static_assets: Optional["str" | "os.PathLike[str]" | dict[str, Path]] = None,
         debug: bool = False,
     ) -> None:
+        # Used to store callbacks to be called when the app is shutting down (according
+        # to the ASGI lifespan protocol)
+        self._exit_stack = AsyncExitStack()
+
         if server is None:
             self.server = noop_server_fn
         elif len(signature(server).parameters) == 1:
@@ -208,10 +215,16 @@ def init_starlette_app(self) -> starlette.applications.Starlette:
         starlette_app = starlette.applications.Starlette(
             routes=routes,
             middleware=middleware,
+            lifespan=self._lifespan,
         )
 
         return starlette_app
 
+    @asynccontextmanager
+    async def _lifespan(self, app: starlette.applications.Starlette):
+        async with self._exit_stack:
+            yield
+
     def _create_session(self, conn: Connection) -> Session:
         id = secrets.token_hex(32)
         session = Session(self, id, conn, debug=self._debug)
@@ -243,6 +256,27 @@ def run(self, **kwargs: object) -> None:
     async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
         await self.starlette_app(scope, receive, send)
 
+    def on_shutdown(self, callback: Callable[[], None]) -> Callable[[], None]:
+        """
+        Register a callback to be called when the app is shutting down. This can be
+        useful for cleaning up app-wide resources, like connection pools, temporary
+        directories, worker threads/processes, etc.
+
+        Parameters
+        ----------
+        callback
+            The callback to call. It should take no arguments, and any return value will
+            be ignored. Try not to raise an exception in the callback, as exceptions
+            during cleanup can hide the original exception that caused the app to shut
+            down.
+
+        Returns
+        -------
+        :
+            The callback, to allow this method to be used as a decorator.
+        """
+        return self._exit_stack.callback(callback)
+
     async def call_pyodide(self, scope: Scope, receive: Receive, send: Send) -> None:
         """
         Communicate with pyodide.

shiny/_datastructures.py

@@ -24,10 +24,14 @@ def put(self, priority: int, item: T) -> None:
         """
         Add an item to the queue.
 
-        Parameters:
-           priority (int): The priority of the item. Higher priority items will
-                           come out of the queue before lower priority items.
-           item (T): The item to put in the queue.
+        Parameters
+        ----------
+        priority
+            The priority of the item. Higher priority items will come out of the queue
+            before lower priority items.
+
+        item
+            The item to put in the queue.
         """
         self._counter += 1
         self._pq.put((-priority, self._counter, item))

shiny/_main.py

@@ -346,6 +346,7 @@ def run_app(
         log_config=log_config,
         app_dir=app_dir,
         factory=factory,
+        lifespan="on",
         **reload_args,  # pyright: ignore[reportGeneralTypeIssues]
         **kwargs,
     )

shiny/_validation.py

@@ -1,25 +1,29 @@
 from __future__ import annotations
 
-from typing import TypeVar, overload
+from typing import Literal, TypeVar, overload
 
 from ._docstring import add_example
-from .types import SilentCancelOutputException, SilentException
+from .types import (
+    SilentCancelOutputException,
+    SilentException,
+    SilentOperationInProgressException,
+)
 
 T = TypeVar("T")
 
 
 @overload
-def req(*, cancel_output: bool = False) -> None:
+def req(*, cancel_output: bool | Literal["progress"] = False) -> None:
     ...
 
 
 @overload
-def req(*args: T, cancel_output: bool = False) -> T:
+def req(*args: T, cancel_output: bool | Literal["progress"] = False) -> T:
     ...
 
 
 @add_example()
-def req(*args: T, cancel_output: bool = False) -> T | None:
+def req(*args: T, cancel_output: bool | Literal["progress"] = False) -> T | None:
     """
     Throw a silent exception for falsy values.
 
@@ -51,8 +55,10 @@ def req(*args: T, cancel_output: bool = False) -> T | None:
 
     for arg in args:
         if not arg:
-            if cancel_output:
+            if cancel_output is True:
                 raise SilentCancelOutputException()
+            elif cancel_output == "progress":
+                raise SilentOperationInProgressException()
             else:
                 raise SilentException()
 

shiny/_versions.py

@@ -1,5 +1,5 @@
-shiny_html_deps = "1.8.0"
-bslib = "0.6.1.9000"
+shiny_html_deps = "1.8.0.9000"
+bslib = "0.6.1.9001"
 htmltools = "0.5.7"
 bootstrap = "5.3.1"
 requirejs = "2.3.6"

shiny/api-examples/extended_task/app.py

@@ -0,0 +1,49 @@
+import asyncio
+from datetime import datetime
+
+from shiny import reactive, render
+from shiny.express import input, ui
+
+ui.h5("Current time")
+
+
+@render.text
+def current_time():
+    reactive.invalidate_later(1)
+    return datetime.now().strftime("%H:%M:%S")
+
+
+with ui.p():
+    "Notice that the time above updates every second, even if you click the button below."
+
+
+@ui.bind_task_button(button_id="btn")
+@reactive.extended_task
+async def slow_compute(a: int, b: int) -> int:
+    await asyncio.sleep(3)
+    return a + b
+
+
+with ui.layout_sidebar():
+    with ui.sidebar():
+        ui.input_numeric("x", "x", 1)
+        ui.input_numeric("y", "y", 2)
+        ui.input_task_button("btn", "Compute, slowly")
+        ui.input_action_button("btn_cancel", "Cancel")
+
+    @reactive.Effect
+    @reactive.event(input.btn, ignore_none=False)
+    def handle_click():
+        # slow_compute.cancel()
+        slow_compute(input.x(), input.y())
+
+    @reactive.Effect
+    @reactive.event(input.btn_cancel)
+    def handle_cancel():
+        slow_compute.cancel()
+
+    ui.h5("Sum of x and y")
+
+    @render.text
+    def show_result():
+        return str(slow_compute.result())

shiny/express/ui/__init__.py

@@ -59,6 +59,8 @@
     input_select,
     input_selectize,
     input_slider,
+    bind_task_button,
+    input_task_button,
     input_text,
     input_text_area,
     insert_accordion_panel,
@@ -78,6 +80,7 @@
     update_select,
     update_selectize,
     update_slider,
+    update_task_button,
     update_text,
     update_text_area,
     update_navs,
@@ -190,6 +193,8 @@
     "input_select",
     "input_selectize",
     "input_slider",
+    "bind_task_button",
+    "input_task_button",
     "input_text",
     "input_text_area",
     "insert_accordion_panel",
@@ -209,6 +214,7 @@
     "update_select",
     "update_selectize",
     "update_slider",
+    "update_task_button",
     "update_text",
     "update_text_area",
     "update_navs",

shiny/reactive/__init__.py

@@ -1,4 +1,5 @@
 from ._core import (  # noqa: F401
+    Context,
     isolate,
     invalidate_later,
     flush,
@@ -19,9 +20,11 @@
     Effect_,  # pyright: ignore[reportUnusedImport]
     event,
 )
+from ._extended_task import ExtendedTask, extended_task
 
 
 __all__ = (
+    "Context",
     "isolate",
     "invalidate_later",
     "flush",
@@ -36,4 +39,6 @@
     "effect",
     "Effect",
     "event",
+    "ExtendedTask",
+    "extended_task",
 )