Catch undeclared (unimported) absolute paths

[dcecile]

I'd like to have all absolute module usages declared via imports. Are there any existing lints that can do this? I've tried absolute_path but it didn't work [1].

Suppose that this is my whole file:

pub fn get_mime_type(ext: &str) -> Option<mime::Mime> {
  if ext == "html" {
    Some(mime::TEXT_HTML)
  } else {
    None
  }
}

I want Clippy to complain until the absolute module is explicitly imported:

use mime;

pub fn get_mime_type(ext: &str) -> Option<mime::Mime> {
  if ext == "html" {
    Some(mime::TEXT_HTML)
  } else {
    None
  }
}

---

[1] absolute_paths with absolute-paths-max-segments = 1 finds the problem, but does not allow resolving it adding an import line.

Instead it requires all children to be imported individually (not something I want to force):

use mime::Mime;
use mime::TEXT_HTML;

pub fn get_mime_type(ext: &str) -> Option<Mime> {
  if ext == "html" {
    Some(TEXT_HTML)
  } else {
    None
  }
}

[flip1995]

I would consider the use mime+mime::Mime suggestion as introducing an unused import. I'm more surprised that rustc doesn't warn about this. Why do you want to import it explicitly?

[dcecile]

I like the convention (from other programming languages) of having all module references listed at the top of the file. This gives me a good way at a glance to get initial context for the code in the file.

I'm also trying to avoid the Ruby on Rails autoloading pattern where "application classes and modules are just available everywhere without require calls".

[flip1995]

The Ruby on Rails thing is not a pattern that works in Rust. If you don't import something, you can only access it through the full path, which is crate::[modules::]*Item.

Back in Rust 2015, if you want to use something from an extern crate A, you had to write extern crate A;. Rust 2018 got rid of this restriction and made it more convenient to use something from an extern crate. What you're asking is pretty much a lint that adds this back with use statements.

I don't think this lint would get a lot of use. But I'd accept it as an restriction lint, if you were to open a PR for it :)

[dcecile]

Got it, thanks!