Intention to nest/flatten imports

[matklad]

use std::error::Error;
use std::io::Write;
use std::path::PathBuf;

<-->

use std::{
    error::Error,
    io::Write,
    path::PathBuf,
};

[dvtomas]

In an ideal world, there would be a configurable import optimizer (see also #2259), that would be able to group imports by std/cargo crates/workspace crates/local imports, sorting imports in each group, nesting/flattening them according to the settings, removing curly braces for single imports etc. Unused imports should be automatically removed. When doing a move or copy refactoring to another file, relevant imports should be copied as well. All reformatting and removing unused imports should happen just on pressing Ctrl-Alt-O, one should almost never have to touch the imports section manually, that is a job for a machine, not for human. This is how it works in the Scala plugin, I've used that for a couple of years so now I see just how much time is wasted by unnecessary manual import maintenance. I'm really looking forward this area being worked on. That said, even the "Import" action for unknown symbols has been a huge help, thank you for that!

Sorry for the digress. IMO this should be a configuration setting in an automatic import optimizer, not an intention, at least in the long run.

[majecty]

I impelmented NestUseStatementsIntention.
You can find it at #2938

When implementing the feature, I met some issues.

1. Should we nest use statements full depth?

full depth

use std::{
    io::Write,
    sync::{
      Arc,
      Mutex
    },
};

only 1 depth

use std::{
    io::Write,
    sync::Arc,
    sync::Mutex,
};;

2. Should we preserve statements order or sort them by dictionary order?

If someone has an opinion, please say it freely.

[majecty]

I implemented nest intention to only nest 1 depth and preserve original order.

[majecty]

@vlad20012
This issue's subject is "nest/flatten imports".
An intention that flattens imports is not implemented yet.
I think this issue should be reopened.

[vlad20012]

Oh, I'm sorry

[fan-tom]

Are we need to add an inspection to show programmer that nesting is possible? Because I even didn't know about this feature until I saw that issue

[fan-tom]

There is bug when nesting use statements like this

use foo;
use foo::bar;

transformed to

use foo::{foo, bar};

instead of

use foo::{self, bar};

[stepancheg]

It would be helpful if intellij-rust had the opposite intention: expand grouped imports into one import per line.