rustfmt fails with errors "left behind trailing whitespace"

[sdht0]

I have rustfmt-preview installed on the nightly toolchain (rustc 1.30.0-nightly (3edb355 2018-08-03)) using rustup.

Running cargo +nightly fmt on the crate: https://github.com/frankmcsherry/differential-dataflow results in numerous "left behind trailing whitespace" errors. Some sample errors:

internal error: left behind trailing whitespace
  --> [..]/differential-dataflow/src/algorithms/prefix_sum.rs:70
   |
70 |         .iterate(|ranges| 
   |                          ^
warning: rustfmt may have failed to format. See previous 1 errors.

  --> [..]/differential-dataflow/examples/seb.rs:37
   |
37 |       let cooccurrences = 
   |                          ^
  --> [..]/differential-dataflow/examples/seb.rs:44
   |
44 |       let row_sums = 
   |                     ^

  --> [..]/differential-dataflow/examples/dataflow.rs:35
   |
35 |             let (tweet_input, tweets) = scope.new_collection(); 
   |                                                                ^

[topecongiro]

rustfmt is failing due to this line.

[topecongiro]

wrap_str checks the width of formatted code, and veto if it exceeds max width. Currently it does not distinguish between normal code and comments. I think that it should skip checking the width of the comment.

https://github.com/rust-lang-nursery/rustfmt/blob/b2a80f99426363c092968ef1b4e771c159d7aa1b/src/utils.rs#L350-L358

[sdht0]

Thank you!

[sdht0]

Hi. I think this bug still exists.

% rustfmt -V    
rustfmt 0.99.2-nightly (5c9a2b6 2018-08-07)

% cargo fmt
internal error: left behind trailing whitespace
  --> [...]/differential-dataflow/src/algorithms/prefix_sum.rs:69
   |
69 |     unit_ranges.iterate(|ranges| 
   |                                 ^

warning: rustfmt may have failed to format. See previous 1 errors.

[topecongiro]

Thanks! Looks like there was another issue when there is comment between closure's argument list and its body.

E.g.

|foo|
// comment
foo + 3;

[sdht0]

You're welcome. Before rustfmt 1.0, is there any plan to run https://github.com/rust-lang-nursery/crater but for rustfmt? That would actually highlight any bugs like this and also ones that result in compilation/test failures.

[scampi]

With the file below, the error is a bit different, but also more informative:

fn main() {
    let toto = |foo|
        // my comment
        foo + 3;
}

The error:

internal error: not formatted because a comment would be lost
 --> /home/yfful/documents/code/rustfmt/issue2896.rs:2
  |
2 |     let toto = |foo|
  |
  = note: set `error_on_unformatted = false` to suppress the warning against comments or string literals

Tested with rustfmt 0.99.2-nightly (2db2327a 2018-08-16).

[sdht0]

Does not look related, but rustfmt is also failing to format the long lines https://github.com/frankmcsherry/differential-dataflow/blob/master/src/trace/implementations/ord.rs#L210 and https://github.com/frankmcsherry/differential-dataflow/blob/master/src/trace/implementations/ord.rs#L301. The rest of the file seems to have been correctly formatted. Should I open a new bug report?

[sdht0]

Are bugs like this not going to be fixed before the 1.0.0 release? rustfmt 1.0.0-stable (4a4e508 2018-11-29) still has this bug and I guess the other open issues marked bug.