Switch to dependency-groups

[paddyroddy]

Fixes #570. Move to the modern [dependency-groups] syntax for non-user facing additional dependencies. See PEP 735.

[Copilot]

Pull Request Overview

This PR modernizes dependency management by migrating from the legacy [project.optional-dependencies] syntax to the new [dependency-groups] format introduced in PEP 735. This change affects how development, documentation, and testing dependencies are declared and installed.

• Replaces optional-dependencies with dependency-groups in pyproject.toml files
• Updates tox configuration to use dependency_groups instead of extras
• Updates installation commands in documentation to use --group flags instead of extras syntax

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
{{cookiecutter.project_slug}}/pyproject.toml	Migrates dependency declarations from optional-dependencies to dependency-groups and updates tox configuration
tutorial.md	Updates installation command examples to use --group syntax
tests/data/test_package_generation/pyproject.toml	Applies the same dependency-groups migration to test data
README.md	Updates quick start installation command to use --group syntax

[samcunliffe]

This should go together with

• #578

in a new release.

[samcunliffe]

Ouch.

[paddyroddy]

Ouch.

Sorry, was trying to distribute load!

[matt-graham]

As far as I can tell the --group option was only added to uv pip install in version v0.8.1, which was released yesterday? And it is only available in pip install from v25.1 (released in April 2025). As it's quite likely users won't have the latest uv and/or pip versions installed, it might be worth adding a note to instructions in tutorial and README that if you get an error when using the --group argument you may need to update you version of uv / pip.

[paddyroddy]

uv added support in v0.6.7 which was released 17/03/2025. I can add the note, but most users (especially on uv) I would expect to be up-to-date.

[paddyroddy]

Link checker failing is unrelated

[p-j-smith]

Very nice, a couple of suggestions but nothing blocking

[matt-graham]

Looks good to me!