bug: imports_granularity = "Module"/"Crate"/"One" crash code when de-duplicate dependencies

[Sunt-ing]

Recently, I enabled a rustfmt rule:

imports_granularity = "Module"

After I re-fmt, the code failed to be compiled. And thus I found an unexpected rustfmt behaviour:

before fmt:

use risingwave_pb::data::DataType;
use risingwave_pb::data::DataType as DataTypeProst;

after fmt:

use risingwave_pb::data::DataType as DataTypeProst;

But the codes that use "DataType" are not changed.

I don't think that rustfmt should turn the correct code into incorrect in any condition.

[TennyZhuang]

Can you provide a reproducible example?

[Sunt-ing]

Can you provide a reproducible example?

Ok, will do it soon.

[Sunt-ing]

Can you provide a reproducible example?

I created a repo to reproduce this bug: https://github.com/Sunt-ing/rustfmt_bug_example

[skyzh]

Can you provide a reproducible example?

I created a repo to reproduce this bug: https://github.com/Sunt-ing/rustfmt_bug_example

Consider creating a single file for this issue, which is easier to test and reproduce. e.g.,

https://github.com/rust-lang/rustfmt/blob/master/tests/source/imports_granularity_crate.rs
https://github.com/rust-lang/rustfmt/blob/master/tests/target/imports_granularity_crate.rs

[Sunt-ing]

@skyzh Good advice. I will try to do that.

[Sunt-ing]

@skyzh Since the bug occurs when imports_granularity = "Module", I think it's hard to reproduce it within a single file. I'd like to leave it to the one who wants to fix it after the bug is verified. He or she could create such a file as a test.

[TennyZhuang]

@skyzh Since the bug occurs when imports_granularity = "Module", I think it's hard to reproduce it within a single file. I'd like to leave it to the one who wants to fix it after the bug is verified. He or she could create such a file as a test.

In fact, rustfmt always accept a single file as input, and cargo fmt call rustfmt on all files. So it should always reproduce on a single file.

[Sunt-ing]

OK, I created one. This code snippet will crash if you format it with any one of the following options:

• imports_granularity = "Module"
• imports_granularity = "One"
• imports_granularity = "Crate"

Yes, imports_granularity = "Item" will not crash it.

#![allow(dead_code)]
mod a {
    pub mod b {
        pub struct Data {
            pub a: i32,
        }
    }

    use crate::a::b::Data;
    use crate::a::b::Data as Data2;

    pub fn data(a: i32) -> Data {
        Data { a }
    }

    pub fn data2(a: i32) -> Data2 {
        Data2 { a }
    }

    #[cfg(test)]
    mod tests {
        use super::*;

        #[test]
        pub fn test() {
            data(1);
            data2(1);
        }
    }
}