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0 pointsskohan5y ago0 comments

> mod.rs isn't needed anymore;

So I'm not sure I'm a fan of this either. So now for a module with sub-modules, part of it is defined in the top-level directory, and part of it is defined in a sub-directory. Now if I want to move a module from one directory to another, I have to move two items in the file system.

> it turns out many people like to "comment out" entire modules when doing big refactorings.

It seems to me it would be much better to have an "exclude.rs" file or something to opt out of a sensible default rather than forcing extra work in the common case just to support the common case. Or else you could still allow a mod.rs if you want to be explicit about your module contents, and just assume it includes everything in the directory if it's missing

> There are also some interesting edge cases, for example, you can use a #[path] attribute on a module to change what the path to the file is; without a mod statement, it's not clear where that would go.

Again, I don't think a design should be optimized to support interesting edge cases. It should make the common case as simple as possible. If edge cases need to be supported, I'm sure a solution can be found

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6 comments · 2 top-level

steveklabnik5y ago· 4 in thread

I am not saying you should love the module system, just trying to provide some context.

(Everyone seems to love and/or hate the module system for various, opposing reasons. It is a great mystery to me. Explaining the module system is like, kind of my white whale.)

skohanOP5y ago

Yeah I just think it’s a trend with rust where when a new user complains about a beginner-unfriendly feature, often they are met with an explanation of some esoteric benefit.

I just wonder how much of that is as-hoc reasoning, and it doesn’t seem like it’s a particularly good sign.

steveklabnik5y ago

I thought this way too until I saw a bunch of people praising how easy the module system was because they felt it was very similar to Python's. I don't know Python well so I can't speak to it.

My working theory: each language does modules in a different way. People think "Oh, a module system, I know this" and then run into issues when it works differently than their language. Just a theory though, I have not been able to validate it, or to figure out an explanation that works for all people.

And yes, more generally: as Rust continues to grow, more and more people will hit more and more edge cases, and they cannot always be fixed, thanks to being backwards compatible. That's just how things are as they grow up. More and more users also brings more and more use cases. It's a feedback loop.

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nicoburns5y ago

I actually the module system is one of the few exceptions where it's actually poorly designed. It could very easily have a 1:1 mapping to the filesystem with no need to declare modules to use them. Lot's of people apparently don't like that idea, but most other module systems do it that way, and IMO it would be a lot more intuitive.

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chmod6005y ago

Rust has an RFC process, which is great in many ways. But for something like a module system where everyone has an opinion, it can result in an over-engineered solution that tries to satisfy everyone.

est315y ago

> > mod.rs isn't needed anymore;

I think the main reason why the foo.rs foo/bar.rs stuff was done was so that the tabs in an editor have informative headings. Instead of ten times mod.rs you have foo.rs, baz.rs, test.rs and so on. Personally I don't like it either (for the same reason as you) but the old way is still possible, even on the 2018 edition, so that's what I use.

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