prettier-plugin-nunjucks VS darker

Yes, there’s Prettier. For Jinja, you can try the Nunjucks plugin.

Thanks for your suggestions. I have gone through the GitHub issue that you have mentioned. From there I got to know about this plugin https://github.com/akaihola/darker

For Python, Darker does that by applying Black only to changed areas of the code. Maybe the same approach could be used for rustfmt by creating a separate tool?

Not an answer to your question but in the specific case of black you can instead use: https://github.com/akaihola/darker

For instance, we have a number of interesting features planned for the 1.5.0 release of Darker, a tool for running Black/isort/pylint/flake8 but limiting to only lines modified between two given Git commits.

I knew one library using "composite". - Darker: https://github.com/akaihola/darker/blob/master/action.yml - More details here: https://docs.github.com/en/actions/creating-actions/creating-a-composite-action

There's also Darker for only reformatting (using Black) the lines modified by commits.

Assuming the range you're interested in is a range with your changes, you should look at darker.

Yeah that's how we've used it. The results need manual checking, but together with darker https://github.com/akaihola/darker that's how we've been slowly ratcheting our Django monolith into a typed codebase.