Debug2

debug2 is a pretty printing crate based on std::fmt

Why not just use Debug

The Debug trait is good, but the problem is it is not very good at nested stuctures. Either you use {:?} and get a line that is too long, or too many lines with not enough information on them.

rust let complex_structure = vec![ vec![Some(1), Some(2), Some(3), None], vec![Some(2), None], vec![Some(4), Some(7)], vec![Some(1), Some(2), Some(3), None], ]; let one_line = format!("{:?}", complex_structure); assert_eq!(one_line, "[[Some(1), Some(2), Some(3), None], [Some(2), None], [Some(4), Some(7)], [Some(1), Some(2), Some(3), None]]"); let many_lines = format!("{:#?}", complex_structure); assert_eq!(many_lines, "[ [ Some( 1, ), Some( 2, ), Some( 3, ), None, ], [ Some( 2, ), None, ], [ Some( 4, ), Some( 7, ), ], [ Some( 1, ), Some( 2, ), Some( 3, ), None, ], ]")

debug2 aims to be a third alternative, that gets this correct.

rust use debug2::pprint; let complex_structure = vec![ vec![Some(1), Some(2), Some(3), None], vec![Some(2), None], vec![Some(4), Some(7)], vec![Some(1), Some(2), Some(3), None], vec![Some(2), None], vec![Some(4), Some(7)], vec![Some(1), Some(2), Some(3), None], vec![Some(2), None], vec![Some(4), Some(7)], ]; assert_eq!( pprint(complex_structure), "\ [ [Some(1), Some(2), Some(3), None], [Some(2), None], [Some(4), Some(7)], [Some(1), Some(2), Some(3), None], [Some(2), None], [Some(4), Some(7)], [Some(1), Some(2), Some(3), None], [Some(2), None], [Some(4), Some(7)], ]" );

debug2 provides a debug2::Debug trait, which can be derived on your types, and is implemented for common types in std.

Once your types implement debug2::Debug, you can use debug2::pprint to convert them to a string.

You can also manually implement Debug, using a subset of the API in std::fmt::Formatter

Limitations

• Speed: While doing this will always mean extra work, this crate is paticularly inefficient.
• Prevalence: Almost every type implements std::fmt::Debug, but not this type
• The derive isn't great: The derive macro for std::fmt::Debug works everywhere. This one is kind of basic, and will probably not work everywhere it should.

Prior art

• std::fmt, where much of the code comes from
• pprint from python , which showed that this sort of thing is doable and great.
• ojg, whose pretty module is the basis for this whole thing.

License

^{Licensed under either of Apache License, Version 2.0 or MIT license at your option.}

_{Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Debug2 by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.}