AttributeError: module 'app' has no attribute 'app'

[dlavrent]

Hello -- I am trying to deploy a basic py-shiny app on an Oracle Cloud virtual machine (aarch64, Ubuntu 22.04) but am running into the following error when I try to access my app on another computer at <my-virtual-machine-ip>:3838/my_shiny_apps/basic-app/

su: ignoring --preserve-environment, it's mutually exclusive with --login
Using Python 3.10.13 at /home/shiny/anaconda3/envs/shiny310/bin/python
Traceback (most recent call last):
  File "/usr/local/shiny-server/python/SockJSAdapter.py", line 204, in <module>
    run()
  File "/usr/local/shiny-server/python/SockJSAdapter.py", line 197, in run
    app = getattr(app_module, "app")
AttributeError: module 'app' has no attribute 'app'

The app.py that I am trying to deploy:

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

ui.panel_title("Hello Shiny!")
ui.input_slider("n", "N", 0, 100, 20)

@render.text
def txt():
    return f"n*2 is {input.n() * 2}"

In case it's useful, my /etc/shiny-server/shiny-server.conf has the following lines pointing to a virtual environment that I am wondering is what is causing the issue:

python /home/shiny/anaconda3/envs/shiny310/;
run_as shiny;

However, if in my virtual machine I activate my virtual environment and run the app locally, shiny run -h 0.0.0.0, then I can access my app from another computer's browser just fine when I connect to <my-virtual-machine-ip>:8000.

I see that someone else has posted this error in recent days as well: https://community.rstudio.com/t/problem-with-deploying-example-app-with-shiny-server-module-app-has-no-attribute-app/181974

I'd appreciate any guidance! This is my first foray into using virtual machines/ARM processors too.

My virtual environment uses python 3.10.13 and shiny 0.7.1.

[wch]

I believe the error message you're seeing is related to the app being a Shiny Express (as opposed to Shiny Core) app.

Just to make sure it has something to do with Shiny Express: Have you tried deploying a Shiny Core app? Here is a basic one you can use:

from shiny import App, render, ui

app_ui = ui.page_fixed(
    ui.input_slider("val", "Slider label", min=0, max=100, value=50),
    ui.output_text_verbatim("slider_val")
)

def server(input, output, session):
    @render.text
    def slider_val():
        return f"Slider value: {input.val()}"

app = App(app_ui, server)

[dlavrent]

Thank you -- I tried deploying a Core version of the basic slider app and it works just fine.

I converted a more complicated Express app to Core and now that works fine too.

[wch]

It seems that Shiny Server Open Source does not yet support for Shiny Express apps. However, you can actually wrap your Shiny Express app so that it looks like a Shiny Core app.

If you name your Shiny Express app file from above express_app.py, and then add the following file as app.py, it should work:

## app.py ##
from pathlib import Path
from shiny.express._run import wrap_express_app

# Create a shiny.App object from the Shiny Express app file
app = wrap_express_app(Path(__file__).parent / "express_app.py")

[jcheng5]

Shoot, that’s quite an oversight, sorry. I’ll add it to the list.

[jcheng5]

PR is here: https://github.com/rstudio/shiny-server/pull/566