Add session.clientdata; allow access to input names via dir()

[cpsievert]

Closes #623
Closes #711

Here's an example to replicate the one on this page https://shiny.posit.co/r/articles/build/client-data/

app.py

# pyright: reportUnknownMemberType=false, reportUnknownVariableType=false
import matplotlib.pyplot as plt
import numpy as np

from shiny.express import input, render, session, ui

with ui.sidebar(open="closed"):
    ui.input_slider("obs", "Number of observations:", min=0, max=1000, value=500)

ui.markdown(
    """
#### `session.clientdata` values

The following methods are available from the `session.clientdata` object and allow you
to reactively read the client data values from the browser.
"""
)


@render.code
def clientdatatext():
    return f"""
    .url_hash()         -> {session.clientdata.url_hash()}
    .url_hash_initial() -> {session.clientdata.url_hash_initial()}
    .url_hostname()     -> {session.clientdata.url_hostname()}
    .url_pathname()     -> {session.clientdata.url_pathname()}
    .url_port()         -> {session.clientdata.url_port()}
    .url_protocol()     -> {session.clientdata.url_protocol()}
    .url_search()       -> {session.clientdata.url_search()}
    .pixelratio()       -> {session.clientdata.pixelratio()}

    .output_height("myplot")       -> {session.clientdata.output_height("myplot")}
    .output_width("myplot")        -> {session.clientdata.output_width("myplot")}
    .output_hidden("myplot")       -> {session.clientdata.output_hidden("myplot")}
    .output_bg_color("myplot")     -> {session.clientdata.output_bg_color("myplot")}
    .output_fg_color("myplot")     -> {session.clientdata.output_fg_color("myplot")}
    .output_accent_color("myplot") -> {session.clientdata.output_accent_color("myplot")}
    .output_font("myplot")         -> {session.clientdata.output_font("myplot")}
    """


@render.plot
def myplot():
    plt.figure()
    plt.hist(np.random.normal(size=input.obs()))  # type: ignore
    plt.title("This is myplot")

TODO

• Unit test using the app provided
• Test this works with Express
• How to best document? Translate https://shiny.posit.co/r/articles/build/client-data/ to Python?
  • Adding to API reference seems good enough for now

[gadenbuie]

Suggested change

	def clientdatatext():
	cdata = session.clientdata
	return "\n".join([f"{name} = {cdata[name]()}" for name in reversed(dir(cdata))])
	def client_data_text():
	client_data = session.clientdata
	return "\n".join([
	f"{name} = {client_data[name]()}" for name in reversed(dir(client_data))
	])

To avoid CDATA vibes.

[gadenbuie]

We don't get autocomplete for session.clientdata, right? So you can use dir() to find out the methods but you won't get autocomplete for session.clientdata.url_*(). The autocomplete would be helpful but isn't a blocker.

[cpsievert]

Nope, no autocomplete. And agreed, it'd be useful, but I also don't see a low effort way to faithfully type those values (not to mention them easily getting out of sync when shiny.js changes).

[cpsievert]

I guess maybe it'd be worth having a ClientData class though so we can at least make them discoverable through the API reference?

class ClientData(Inputs):
     "TODO: docs here"
    pass

[cpsievert]

Actually, hold on, maybe there is a sensible thing to do for autocomplete as well...

[gadenbuie]

Yeah I also don't think all the values need to be accessible in autocomplete, but it'd be useful to have the url_ and other stable data as well

[cpsievert]

Thanks for the nudge here -- e1e4526 takes a more typing and documentation friendly approach

[gadenbuie]

Could you test url_search, url_hash_initial and url_hash here? Those are all more valuable and likely to be used than, say, url_protocol.

[cpsievert]

There's a shinycoreci app that already does a good job of covering the front end logic (see comment added in a30b8c8), so I'd rather not redo it

[cpsievert]

@gadenbuie this is ready for another look -- thanks for the suggestions!