Support local Python application development

[seeM]

This PR adds support for local Python application development for the following frameworks:

• Streamlit
• Dash
• Gradio
• FastAPI
• Flask

This is facilitated by a new extension: positron-run-app.

Addresses #4557, #4555, #3023, #3027, #3024.

Screen.Recording.2024-09-13.at.19.23.43.mov

QA notes

1. Open an application developed using one of the supported frameworks.
2. Run the relevant "Python: Run X App in Terminal" command. It should also be the default action if you click the run button in the editor menu.
3. It should create a terminal named after the framework, and automatically show the app in the Viewer pane once its ready.

Here are example apps for all of the supported frameworks:

Streamlit

import streamlit as st
x = st.slider('x')
st.write(x, 'squared is', x * x)

Dash

from dash import Dash, html
app = Dash()
app.layout = [html.Div(children='Hello World')]
if __name__ == '__main__':
    app.run(debug=True)

Gradio

import gradio as gr
def image_classifier(inp):
    return {'cat': 0.3, 'dog': 0.7}
demo = gr.Interface(fn=image_classifier, inputs="image", outputs="label")
demo.launch()

FastAPI

from fastapi import FastAPI
app = FastAPI()
@app.get("/")
async def root():
    return {"message": "Hello World"}

Flask

from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello_world():
    return "<p>Hello, World!</p>"

Next steps: Workbench integration

To support Workbench, we'll need to update runApplication to detect if we're in Workbench, and if so, find a free port and corresponding proxied URL (possibly related to #4274) and pass them both to getTerminalOptions.

[isabelizimm]

I can go over this a bit deeper on Monday, but I think it seems like a reasonable start!

Potential other names I thought of are positron-app-runner and positron-app-viewer, although I don't think the current one is too bad 😄

[seeM]

CI was failing due to cache issues so I've bumped the extensions cache key again in dd507f7 and let @midleman know.

[seeM]

Next CI error is because the test is running outside of a workspace. I can't figure out why, since that's not the case locally. Will try to debug next week or disable these tests in CI for now so we can merge once this is ready.

[isabelizimm]

tried out with sample scripts and some community-built applications, and everything seems to run as expected!

side note: when I first built Positron, I ran into this error. After restarting it disappeared. noting in case this pops up again somewhere, but it seems unrelated to these changes

Command failed: . /Users/isabelzimmerman/code/positron-scratch/scratchvenv/bin/activate && echo 'e8b39361-0157-4923-80e1-22d70d46dee6' && python /Users/isabelzimmerman/code/positron/extensions/positron-python/python_files/printEnvVariables.py Debugger listening on ws://127.0.0.1:52539/19a0b899-0894-458d-8ae5-8a307458405d For help, see: https://nodejs.org/en/docs/inspector Debugger attached.

[sharon-wang]

Testing on Workbench

(example apps from PR description)

Streamlit

Seems to be running just fine!

Dash

Message that popped up before running Dash app

After pip install python-dotenv and running Dash app

Gradio

• app is loaded at correct path, but some of the files referenced in the app HTML are not loaded from the right path (the /s/<string>/p/<string> proxy path is missing in some of the hrefs)

FastAPI

Opening the proxied url directly

Changing the URL in the Viewer

• this seems to imply that we're hitting the proxy/<port> path instead of the /s/<string>/p/<string> proxy path at some point. Direct access to /proxy/<port> is blocked on Workbench, so that's probably why it was failing to make the request.

Flask

Dialog that shows when I save the python file for the Flask app

After applying additional code snippet and running the app