darker VS rustfmt

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.

The author provides very surface-level criticism of two Rust tools, but they don't look into why those choices were made.

With about five minutes of my time, I found out:

wrap_comments was introduced in 2019 [0]. There are bugs in the implementation (it breaks Markdown tables), so the option hasn't been marked as stable. Progress on the issue has been spotty.

--no-merge-sources is not trivial to re-implement [1]. The author has already explained why the flag no longer works -- Cargo integrated the command, but not all of the flags. This commit [2] explains why this functionality was removed in the first place.

Rust is open source, so the author of this blog post could improve the state of the software they care about by championing these issues. The --no-merge-sources error message even encourages you to open an issue, presumably so that the authors of Cargo can gauge the importance of certain flags/features.

You could even do something much simpler, like adding a comment to the related issues mentioning that you ran into these rough edges and that it made your life a little worse, or with a workaround that you found.

Alternatively, you can continue to write about how much free software sucks.

[0]: https://github.com/rust-lang/rustfmt/issues/3347

[1]: https://github.com/rust-lang/cargo/pull/10344

[2]: https://github.com/rust-lang/cargo/commit/3842d8e6f20067f716...

The new style still supports single line let-else, and there is a configuration parameter to make it be on one line also for longer lines.

It seems there is an issue about this dating all the way back from 2018 but yet it still hasn't been fixed.

However since 4179 recent versions should merge configuration files. Not sure what the details / specifics are but if just ignoring the file entirely is not good enough you might give it its own directory and rustfmt.toml file and see if that works.

Could this be be #3863 - Gives up on chains if any line is too long? It might not be, because I can't see a specific "line" that's too long to format, but there's more detail about the exact problem in the issue.

Rustfmt is a tool that formats Rust code in compliance with style guidelines. Its name precisely reflects its purpose. To install rustfmt, you can run rustup component add rustfmt. Once installed, you can execute cargo fmt to format Rust code in your workspace. If you require further information, you can visit rustfmt’s GitHub repository.

code must be formatted with rustfmt.

Yes, some cases are not yet supported (https://github.com/rust-lang/rustfmt/issues/4914).

Just FYI, the let-else suggestions will only work until rustfmt settles on a format for it. So you may be surprised when this happens and it suddenly changes.