Add support for express mode apps #767

wch · 2023-10-17T02:47:46Z

To install:

# First uninstall old version
pip uninstall shiny

pip install git+https://github.com/posit-dev/py-shiny.git@flat-mode#egg=shiny

Express apps can be run with:

shiny run examples/express/app.py

You can also run it with an ASGI server like uvicorn, like so:

SHINY_EXPRESS_APP_FILE="examples/express/app.py" uvicorn shiny.express.app:app

This works because shiny.express.app:app is an ASGI application, and so ASGI servers like uvicorn will be able to use it. However, it is part of the shiny package and can't be user-modified, so the the way you tell it which file to use for the flat app source is by setting SHINY_EXPRESS_APP_FILE.

jcheng5 · 2023-10-17T06:54:07Z

I don't feel comfortable enough with the @no_default_ui decorator to push it to you branch, but here's the implementation:

def no_default_ui(output_renderer: OutputRenderer[OT]) -> OutputRenderer[OT]:
    output_renderer.default_ui = lambda x: ""
    return output_renderer

Bool-on-OutputRenderer route is equally easy.

I put it in shiny/render/transformer/_transformer.py but then made it available from shiny/render/__init__.py.

jcheng5 · 2023-11-08T19:18:44Z

js/page-output/page-output.ts

+    } else {
+      // This is a later run. Reset attributes to their inital state.
+      for (const attr of this.originalBodyTagAttrs) {
+        el.setAttribute(attr.name, attr.value);


Need to also clear added attributes

jcheng5 · 2023-11-08T19:19:49Z

js/page-output/page-output.ts

+      }
+    }
+
+    let content = typeof data === "string" ? data : data.html;


data will never be a string

jcheng5 · 2023-11-08T19:24:20Z

js/page-output/page-output.ts

+
+    // Parse the HTML
+    const parser = new DOMParser();
+    const doc = parser.parseFromString(content, "text/html");


This might be a little slow but whatever

jcheng5 · 2023-11-08T19:50:14Z

shiny/express/app.py

+app: App
+
+
+def __getattr__(name: str):


jcheng5 · 2023-11-08T19:52:06Z

shiny/express/__init__.py

    "output_args",
    "suspend_display",
+    "wrap_express_app",
+    "app",


This seems private

jcheng5 · 2023-11-08T19:55:41Z

shiny/express/_run.py

+    return old_cm
+
+
+class DetectShinyExpressVisitor(ast.NodeVisitor):


Consider rejecting if shiny.App() call is found

jcheng5 · 2023-11-08T19:56:39Z

shiny/express/_run.py

+    return app
+
+
+def is_express_app(app: str, app_dir: str | None) -> bool:


Maybe have a way out as well--environment variable or something to force one mode or another.

jcheng5 · 2023-11-08T19:59:23Z

shiny/express/__init__.py

+# returns the input for the current session. This will work in the vast majority of
+# cases, but when it fails, it will be very confusing.
+def __getattr__(name: str) -> object:
+    if name == "input":


Consider detecting if input, output, or session are requested more than once from the same scope. (using inspect?)

jcheng5 · 2023-11-08T20:13:37Z

shiny/express/_run.py

+    app_ui = ui.page_output("__page__")
+
+    def express_server(input: Inputs, output: Outputs, session: Session):
+        try:
+            dyn_ui = run_express(file)


Suggested change

app_ui = ui.page_output("__page__")

def express_server(input: Inputs, output: Outputs, session: Session):

try:

dyn_ui = run_express(file)

app_ui = run_express(file)

def express_server(input: Inputs, output: Outputs, session: Session):

try:

run_express(file)

The reasons for suggesting this (during live discussion):

HTML dependencies load with the page load which leads to smoother rendering (less fouc)

Downside:

Process startup is slightly slower

Oops, also would need to get rid of render.ui below

jcheng5 · 2023-11-08T20:17:46Z

shiny/express/_run.py

+        file = Path(os.getcwd()) / app_file
+
+    # TODO: title and lang
+    app_ui = ui.page_output("__page__")


Whatever we do, need to catch errors that happen during UI rendering/app.py loading and have the stack trace appear in the console.

jcheng5 · 2023-11-08T20:19:50Z

shiny/express/_run.py

+    sys.displayhook = set_result
+
+    reset_top_level_recall_context_manager()
+    get_top_level_recall_context_manager().__enter__()


This should use with

jcheng5 · 2023-11-08T20:20:02Z

shiny/express/_run.py

+        nonlocal ui_result
+        ui_result = cast(Tag, x)
+
+    sys.displayhook = set_result


Probably this too

jcheng5 · 2023-11-08T20:22:17Z

shiny/express/_run.py

+    reset_top_level_recall_context_manager()
+    get_top_level_recall_context_manager().__enter__()
+
+    file_path = str(file.resolve())


Maybe require this to be absolute rather than resolving it here? Or not, I don't know.

jcheng5 · 2023-11-08T20:23:37Z

shiny/express/_run.py

+    for node in tree.body:
+        if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+            exec(
+                compile(ast.Module([node], type_ignores=[]), file_path, "exec"),


AST loading, transformation, and compiling could be a separate step that we only do once. Then separate step for running each code block, which we do every time.

jcheng5 · 2023-11-08T20:25:41Z

shiny/express/_run.py

+
+
+_top_level_recall_context_manager: RecallContextManager[Tag]
+_top_level_recall_context_manager_has_been_replaced = False


When you use a with layout.foo() function in the wrong setting, you get an unhelpful error message

jcheng5 · 2023-11-08T20:27:34Z

shiny/express/_run.py

+    return ui_result
+
+
+_top_level_recall_context_manager: RecallContextManager[Tag]


Consider making all this state/logic an object/methods

jcheng5 · 2023-11-08T20:30:21Z

shiny/express/_recall_context.py

+            if value is not None:
+                self.args.append(tags.pre(repr(value)))
+
+    def __enter__(self) -> None:


The global context manager object could accumulate the results, and then only decide to create the page at the end.

jcheng5 · 2023-11-08T20:32:30Z

shiny/express/_recall_context.py

+
+        self._prev_displayhook = sys.displayhook
+        # Collect each of the "printed" values in the args list.
+        sys.displayhook = self.append_arg


We should consider just replacing sys.displayhook once, at process start time, with a smart version of our own. And then have that smart version look at a different variable, backed by a contextvar, to decide where things actually go. This would let us keep "displayhooks" straight even when using async logic.

Q: Would this work in Quarto? In JupyterLab?

* main: Update shinylive to v0.1.1 (#825) Deploy dev docs on GitHub Pages (#824) Add docstrings Check for 'app' object in Express mode Use path to app as part of entrypoint for Express apps (#816) Install htmltools from github in CI (#811) Change htmltools dependency to use version number For layout.sidebar, default to open="always" Fix CSS class name Make page_sidebar main area white Update VS Code settings For quarto apps, check for `import *` (#810) Restore workaround for type stubs from typing_extensions Add try-except so parsing doesn't result in error Move is_express_app to separate file Add support for express mode apps (#767) Un-pin pyright version and fix type issues (#800) chore: Penguin app updates (#798) bug(`accordion(multiple=)`): Pass in accordion ID into accordion panel objects for `multiple` functionality (#799)

Add basic flat app support

e85d8cc

wch force-pushed the flat-mode branch from 16a878b to e85d8cc Compare October 17, 2023 02:48

jcheng5 and others added 14 commits October 17, 2023 15:40

Add @suspend_display and @output_args decorators

5297c58

Functions within with, while, try, etc. are displayed

50d6d7f

Call repr() on objects

9d5d70a

Replace Any with object

3cd256d

Ignore type checking for line

03fb00d

Don't print None

9ab79d3

Fix path for flat apps

e09ea98

Move flat.py into flat/

59f04c4

Refactor flat app wrapping code

cb16657

Reorganize

391c8c6

Merge remote-tracking branch 'origin/main' into flat-mode

5736c93

Restructure files

7197199

Add flat.ui module

b5fc438

Add flat.open

84bd0b2

wch force-pushed the flat-mode branch from 880d5dc to 84bd0b2 Compare October 21, 2023 03:47

wch added 4 commits October 21, 2023 09:11

Code cleanup

b1f4ea3

Update exports

d98986f

Remove unused import

090c93d

Remove .open code

d6b9933

wch force-pushed the flat-mode branch from 532f859 to d6b9933 Compare October 25, 2023 16:49

wch added 4 commits October 25, 2023 11:56

Refactor RecallContextManager and components

5aaaa53

Rename shiny.flat.ui to shiny.flat.layout

8982f02

Better typing for RecallContextManager; add some components

105dca4

Rename shiny.flat to shiny.express

9301477

wch force-pushed the flat-mode branch from e8e9960 to 9301477 Compare October 25, 2023 20:53

wch added 2 commits October 25, 2023 15:53

Use release version of htmltools

016901f

Simplify use of __getattr__

068765b

jcheng5 and others added 3 commits November 7, 2023 22:39

Pyright

e8cdc87

Simplify basic express app

ea2bd07

App updates

31a344c