rustfmt fails to format array that contains more than one struct lit which exceeds max_width

[farrel]

Describe the bug

I have a const array of structs. If the array has more than 8 elements rustfmt will not format the file.

To Reproduce

Run rstfmt on the contents of https://gist.github.com/farrel/c982304bdefe5c2ee2c8ee8207a3e0ff

Expected behavior

The file should be formatted.

Meta

• rustfmt version: rustfmt 1.4.17-stable (8a93416 2020-07-20)
• From where did you install rustfmt?: rustup
• How do you run rustfmt: rustfmt, cargo-fmt, vim integration (all fail)

[calebcartwright]

Thanks for the report! However, your diagnosis is not quite correct. rustfmt is bailing on formatting the SOURCES array due to a max_width issue on one of the elements, but it is still formatting the file (you can see this by modifying one of the enum or struct defs - https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=45f220c5df8bb171cef4c3b59db141c1).

The root cause of the problem is that the formatted result for a handful of the AlertSource array elements (specifically the ones for Canada, Phillipines, Spain, and United States) would exceed the default max_width of 100 because of the lengthy organisation string values; it doesn't have anything to do with the number of elements, the element for Canada just happens to be the ninth one. Since rustfmt failed to format one (or more) elements in the array, the entire array is left as-is. There's a handful of cases like these where rustfmt will defer to the programmer to format since the max_width rule would be violated.

If this is array isn't terribly dynamic, you could consider getting it formatted by running rustfmt against it (in a separate file/project) with max_width cranked up to ~130 (I forgot how long the longest string was with indentation), and then copying the formatted result back into your project.

[farrel]

Thanks for the tip. I just called rustfmt from the command line passing in a larger max_width using the --config flag.

[liamcurry]

Here is an extremely simple example that fails to auto-format:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=38be980e3f69577b7119a3e7705ebc54

Source:

const STRS: &[&str] = &[
    "1234512345123451234512345123451234512345123451234512345123451234512345123451234512345123451234",
    
    
    
    
    
];

Removing the last 4 will make it work again.