Comments for pyproject.toml dependencies get shifted unexpectedly

[christeefy]

Summary

Hi there,

I encountered an behaviour where comments for pyproject.toml dependencies gets shifted unexpectedly.

Minimal Reproducible Example

Given an initial pyproject.toml file:

[project]
name = "test-uv"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "fastapi>=0.115.11",
    "jedi>=0.19.2", # This is a test comment
    "typer>=0.15.2"
]

Upon running uv add pydantic (note how pydantic would be inserted right under jedi and the comment), I expect to get:

[project]
name = "test-uv"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "fastapi>=0.115.11",
    "jedi>=0.19.2", # This is a test comment
    "pydantic>=2.10.6", 
    "typer>=0.15.2"
]

Instead, comment associated with jedi has shifted to the line with pydantic:

[project]
name = "test-uv"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "fastapi>=0.115.11",
    "jedi>=0.19.2",  
    "pydantic>=2.10.6", # This is a test comment
    "typer>=0.15.2"
]

Notes

In my testing, the bug occurs only when:

• the comment is applied on a non-terminal dependency — a dependency that isn't the first or last in the list
• a new dependency is inserted right below the commented one

---

Contributing Back

uv is an amazing project, and I'd love to contribute back to it.
I have some Rust experience, but I'm not familiar with the repo structure. If you can so kindly point me to the relevant section/crate in the repo, I'm happy to help resolve this bug 😊

Platform

Darwin 24.3.0 arm64

Version

uv 0.6.8 (c1ef482 2025-03-18)

Python version

Python 3.12.2

[charliermarsh]

Thanks for the nice issue, this does look like a bug in comment handling. I believe the relevant code is in add_dependency in pyproject_mut.rs.

[christeefy]

PR is ready for review, please take a look! 🙏