fix fastapi app path to module conversion on Windows

[sharon-wang]

Summary

• addresses Python fastapi app is not working on windows #5312
• re-enables Python - Verify Basic FastAPI App [C903306] on Windows

Release Notes

New Features

• N/A

Bug Fixes

• Fixes bug in file path to module import path conversion in the Python Extension, which was preventing FastAPI apps from running on Windows when using the App Launcher (Python fastapi app is not working on windows #5312)

QA Notes

Running fastapi_example.py with the App Launcher should now work on Windows.

PR Testing

@:apps

Windows Test Results 🎉

• test run: https://github.com/posit-dev/positron/actions/runs/12486724958/job/34847131287

[github-actions]

E2E Tests 🚀  ^?
This PR will run tests tagged with: @critical @apps

[seeM]

LGTM! Out of curiosity, why didn't path.sep work on Windows?

[sharon-wang]

LGTM! Out of curiosity, why didn't path.sep work on Windows?

Ah yeah, the relativeDir path seems to use UNIX path separators even on Windows 🤷 could be that the path library might be normalizing the path separator?

Example

• relativeDir: workspaces/python_apps/fastapi_example
• path.sep on Windows: \
• relativeDir.split('\\') === ['workspaces/python_apps/fastapi_example'], since the path separator \ isn't found in the string workspaces/python_apps/fastapi_example