uv project creation results in errors

[gublit]

System details: Fedora Linux

Positron and OS details:

Positron Version: 2025.06.0 build 146
Code - OSS Version: 1.100.0
Commit: 5d50f36
Date: 2025-05-27T03:38:37.066Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Linux x64 6.14.8-300.fc42.x86_64

Interpreter details:

uv python 3.12.10

Describe the issue:

After following the steps to create a new python project with uv, only README.md, .gitignore, and .venv are created. No pyproject.toml and uv.lock files are created by positron. These two files are the essence of reproducibility in uv btw. Without them, the project cannot be replicated.

Steps to reproduce the issue:

1. Select new project
2. Set project name and location

• Choose a project type, name and directory
• Initialize git repo

3. Under Set up python environment:

• create new environment
• Select environment type as uv
• Pick python 3.12 as your interpreter.

Expected or desired behavior:

Ideally, positron should create pyproject.toml and uv.lock files to abstract the CLI process of running 'uv init' to create a uv python project

Were there any error messages in the UI, Output panel, or Developer Tools console?

[austin3dickey]

Hey @gublit, thanks for the issue! We are planning to add a bare pyproject.toml as another checkbox option, probably "on" by default. I realize I forgot to create an issue for that, so I'll use this one to track that work!

Regarding a uv.lock file, we'll probably leave that up to the user to create via the CLI. Once there exists a pyproject.toml file in the project, all uv commands will work, including uv add and uv sync. And uv add or uv lock will create the lockfile if it doesn't exist.

[gublit]

Thanks for taking this up. It would really help a lot, especially new users of Positron.

[juliasilge]

We want to keep this scoped quite tightly for 2025.07: only the bare pyproject.toml.

[gublit]

Looking forward to testing it out. Thank you @juliasilge.

[austin3dickey]

Yep, I'll propose the same as what uv init --bare creates:

[project]
name = "<folder_name>"
version = "0.1.0"
requires-python = ">= <chosen_version>"
dependencies = []

[austin3dickey]

For now I think I'll drop the requires-python line because it might create more headaches than it resolves.

[gublit]

After excluding it, how will the project keep track of the python version,
Or the command will initiate a .python-version file in the project directory?

[austin3dickey]

Good question! For 2025.07.0 we want to keep this feature tightly scoped, and keep the file as minimal as possible only to restore access to uv add etc. I don't want this feature to be too opinionated or strict for now.

In the future we want to enhance the template options that Positron offers (see #3248 and #1529). Some of those templates will have stricter opinions about configuring the project. One could imagine different templates having different requires-python requirements; for example, a webapp may need something different from a Python package.

All that said, I realize now that the omission of a requires-python line actually causes some tools like uv to treat the project as if it were requires-python = ">= 3.13", and it gives loud warnings as it does so. This isn't ideal for our default bare configuration because someone could be using 3.9, for example, and uv would be resolving package dependencies that aren't compatible with 3.9.

So we've decided to hardcode this default config creation with requires-python = ">= 3.9", which is the minimum version that Positron currently supports. This is purposely more broad than what uv does because we anticipate there being use cases where someone wants to use the latest Python version in Positron but wants their project to support old versions as well. People can always change this default or create a .python-version file as you suggest. And future templates will do these things for the user too.