Document Cargo.toml formatting

[NickLarsenNZ]

It is good to have consistent formatting for consistency between developers (eg: using rustfmt for ust code) to reduce noise around style in PR reviews.

Automatic formatting is a preference, however exising TOML formatters (as far as we know) apply rules across the whole toml file (and not only Cargo.toml), rather than different rules per section or use case of toml.

For example,

• we would like [dependencies] to be ordered alphabetically
• we would like important [project] attributes to be at the top of the section

So, for now we should document how we expect Cargo.toml to look, to avoid it repeatedly coming up in PRs.

[NickLarsenNZ]

I found some kind of style guide (for reference): https://github.com/rust-lang/rust/blob/master/src/doc/style-guide/src/cargo.md

Eg:

Version-sort key names within each section, with the exception of the
[package] section. Put the [package] section at the top of the file; put
the name and version keys in that order at the top of that section,
followed by the remaining keys other than description in order, followed by
the description at the end of that section.

So

[package]
name = "crate-name"
version = "0.0.1"
# ... otherwise alphabetically sorted here
description = "this crate does nothing"

[NickLarsenNZ]

It looks like many organizations/projects have the same conundrum. There also seems to be some work underway to bring the formatting into rustfmt: rust-lang/rustfmt#5240

Maybe we just need to wait it out?

[sbernauer]

I think we can throw a link to https://github.com/rust-lang/rust/blob/master/src/doc/style-guide/src/cargo.md in our guidelines and call it a day until we got rustfmt support, WDYT?

[sbernauer]

FYI, just saw apache/iceberg-rust#167

[fhennig]

I'm working on this now: #535

@sbernauer taplo looks interesting but I think we can just wait until it'll be native in rustfmt, not worth the effort to add another tool to our build process. If you think it's worth investigating maybe track it in a new issue.

[sbernauer]

but I think we can just wait until it'll be native in rustfmt, not worth the effort to add another tool to our build process

100% agreed