[unstable option] merge_imports

[scampi]

Tracking issue for unstable option: merge_imports

[gnzlbg]

Would it be possible to update this Tracking issue with more information?

For example, why is this unstable? Should this always be opt-in, or is the plan to enable it by default, what remains to be done to make this option stable, etc.

Which PR implemented this (e.g. #2603) ?

There is a closed fmt-rfc: rust-lang/style-team#24 where @nrc said:

I propose that we not do this by default, but tools may offer options to do this.

But that's about it, the merged RFC does not talk about it, so I'd guess there is no merged RFC saying anything about this. Is the next step towards stabilization to merge an RFC about this ? (independently of which direction that RFC goes).

[jrobsonchase]

Assuming the rust compiler is behaving as intended, this can break imports. Currently, these are not semantically equivalent, but rustfmt with merge_imports will format the former into the later:

use alloc::vec; // imports *both* the macro and the module
use alloc::vec::Vec;

use alloc::vec::{self, Vec}; // only imports the module and `Vec`. `vec!` is left out.

[valff]

Perhaps merge_imports shouldn't use self in a leaf position at all? So this

use alloc::vec::{self, Vec};

should always be converted to

use alloc::{vec, vec::Vec};

[stepancheg]

I wish there was a third option: unmerge imports into one import per line.

[faern]

I would love merge_imports to be stabilized. I use it in all my personal and work crates. But if splitting imports is also desired, it should probably be under the same config directive, so probably good to think that through first.