Lint docs tests for unused imports

[sffc]

I've come across a number of docs tests that have unused imports, which can be confusing to clients and developers.

We should clean up unused imports and then prevent them from being added again.

@Manishearth suggested running docs tests with -D warnings or a flag that causes the docs tests to fail if they have unused imports warnings.

[robertbastian]

There are also other lints like unused variables that should definitely be checked.

[Harsh1s]

Hello there! I'd like to work on this issue! Could you please assign this to me?

[robertbastian]

There you go, let me know if you have any questions!

[Harsh1s]

@robertbastian I'm sorry if I sound dumb, I'm new to the project. Just wanted to confirm something. When you say "docs tests", you mean the tutorials in the docs folder right? Also, if I need to do it for all the languages in the tutorials folder, is it possible to run all the tutorials with '-D warnings' to get error when unused imports exist?

Thanks for your help!

[robertbastian]

No, docs tests are the code in Rustdoc, i.e. things like this

icu4x/components/list/src/list_formatter.rs

Lines 97 to 121 in f4fe3c5

	/// ```
	/// use icu::list::*;
	/// # use icu::locid::locale;
	/// # use writeable::*;
	/// let formatteur = ListFormatter::try_new_and_with_length(
	/// &locale!("fr").into(),
	/// ListLength::Wide,
	/// )
	/// .unwrap();
	/// let pays = ["Italie", "France", "Espagne", "Allemagne"];
	///
	/// assert_writeable_parts_eq!(
	/// formatteur.format(pays.iter()),
	/// "Italie, France, Espagne et Allemagne",
	/// [
	/// (0, 6, parts::ELEMENT),
	/// (6, 8, parts::LITERAL),
	/// (8, 14, parts::ELEMENT),
	/// (14, 16, parts::LITERAL),
	/// (16, 23, parts::ELEMENT),
	/// (23, 27, parts::LITERAL),
	/// (27, 36, parts::ELEMENT),
	/// ]
	/// );
	/// ```

. They are run by this CI job:

icu4x/tools/make/tests.toml

Lines 49 to 53 in f4fe3c5

	[tasks.test-docs]
	description = "Run all Rust doctests with all features"
	category = "ICU4X Development"
	command = "cargo"
	args = ["test", "--all-features", "--doc", "--no-fail-fast"]

[sffc]

Fixed by #4628, yes?