add MSRV

[danieleades]

adds an MSRV check to CI

this check ensures that changes to dependencies or syntax in this repo don't inadvertently force downstream users to bump their compiler versions.

the clippy msrv config also prevents clippy from suggesting changes that are not supported by the MSRV toolchain

An MSRV bump should be a patch change before 1.0.0, and a minor change afterwards

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.60%. Comparing base (8ca80dd) to head (9c344b5).
⚠️ Report is 37 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #242 +/- ##
=======================================
Coverage 78.60% 78.60% =======================================
Files 18 18 Lines 589 589 =======================================
Hits 463 463 Misses 126 126 

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[iitsdani]

I wouldn't mind adding MSRV once again, but only if there is a pain-free way to "infer" it.
Is there any official documentation on how to do it?

I tried some time ago, the only tool I found was https://github.com/foresterre/cargo-msrv, which is gloriously failing on my dev machine since it uses rustup and I can't use that (NixOS machine).

If it's something I can't maintain, I'd rather not specify it honestly and just target latest stable always.
I know that's not the nicest stance to take, but better than a broken experience 🤷🏻‍♂️

[danieleades]

I wouldn't mind adding MSRV once again, but only if there is a pain-free way to "infer" it. Is there any official documentation on how to do it?

I tried some time ago, the only tool I found was https://github.com/foresterre/cargo-msrv, which is gloriously failing on my dev machine since it uses rustup and I can't use that (NixOS machine).

I use cargo-msrv, which is pretty straightforward on my machine. Have you tried raising a ticket against the project for NixOS support?

It looks like some work has been done here already, so it may Just Work for you

• No such file or directory (os error 2) when running with nix-shell --pure foresterre/cargo-msrv#187
• cargo-msrv requires rustup to actually run NixOS/nixpkgs#146232
• cargo-msrv: add rustup to propagatedBuildInputs NixOS/nixpkgs#146258

If it's something I can't maintain, I'd rather not specify it honestly and just target latest stable always. I know that's not the nicest stance to take, but better than a broken experience 🤷🏻‍♂️

depends what you mean by 'stable'. For example using variables directly inside format strings was just stabilised, so you can now do

format!("key: {value}");

instead of

format!("key: {}", value);

But if you were to switch to that syntax the moment it was available, you'd break the build for any downstream users that weren't using the very latest stable compiler. Adding an MSRV target gives you a way to tell if you've potentially just broken other people's builds with a PR.

[iitsdani]

Hey @danieleades 👋🏻

Going back to this PR.
How would you feel about adding an Action step to calculate the latest MSRV on the Github Actions runner? 👀

Might be easier in terms of maintenance, and I would be more than willing to add an MSRV version then 👌🏻