[bdickason]

I recently spun up a project in Rust (a small game using Bevy) and the main issues I ran into were around smart defaults for the compiler. I was surprised how many lines I had to add to my cargo.toml to just complete a simple game example.

Some examples:

It defaulted to the fully backwards compatible version (vs 2021) which threw errors as I went through some recent example code.

(I think) I had to add a few lines to my cargo.toml so the compiler would not rebuild bevy every time I recompiled (when I only changed 1 line in my program).

[TheDong]

> It defaulted to the fully backwards compatible version (vs 2021)

"cargo init" and "cargo new" default to the 2021 edition, and have ever since it was stabilized: https://github.com/rust-lang/cargo/pull/9800

Either you accidentally installed a version of cargo from before the 2021 edition was stabilized, or you ran "cargo new --edition <something>", or you started by cloning an out of date project of some sort, in which case it's not really an issue with "defaults".

> smart defaults for the compiler. I was surprised how many lines I had to add to my cargo.toml

Normally this would be a pointlessly pedantic point, but cargo is not the compiler. This thread, the linked title blog post, they are about the rust compiler, not cargo. There's a close relationship, but cargo's defaults aren't necessarily related to what the "next rust compiler" might do.

[bdickason]

Thanks this is helpful!

I started my project without cargo at first and tried to start writing code without a cargo.toml. I was surprised that cairo didn't default to 2021 until I specified it in the .toml file. Good point that cargo init/new would have solved this!

I guess my point about the compiler was that it seems to rely on cargo.toml for many 'optimizations' that I would expect to be defaults. (Examples include the two i mentioned above).

But I'm new to the language and understand that most people will just use `cargo init` and google a few other common cargo.toml settings to improve compile times.

[TheDong]

Ah, yeah, hand-writing a Cargo.toml like that does run into that issue.

However, I don't think the solution is a better default, but rather the solution is time-travel.

Defaulting to the latest edition would mean that any rust library that predates editions would likely break when you imported it (since it would default to an edition that didn't exist when it was written, and editions are allowed to make breaking changes of that sort).

The thing that would fix your issue would be time-traveling back in time to when cargo was created, and making edition a required field of all cargo.toml files that results in an error until you add one. That would have saved you from any trouble.

Rust could also do a python2 -> python3 like transition, where crates from the old "edition not required" world can't be imported anymore at all, but that seems like a very small thing to cause so much ecosystem pain over.