15 releases

0.6.1	Jan 22, 2024
0.5.1	Mar 11, 2023
0.5.0	Jun 12, 2020
0.4.0	Feb 1, 2020
0.1.4	Nov 27, 2018

#859 in Procedural macros

68,401 downloads per month
Used in 57 crates (11 directly)

Apache-2.0 OR MIT

24KB
554 lines

custom_debug

Derive Debug with a custom format per field.

Example usage

Here is a showcase of custom_debugs features:

    use custom_debug::Debug;
    use std::fmt;

    #[derive(Debug)]
    struct Foo {
        #[debug(format = "{} things")]
        x: i32,
        #[debug(skip)]
        y: i32,
        #[debug(with = hex_fmt)]
        z: i32,
        #[debug(skip_if = Option::is_none)]
        label: Option<String>,
    }

    fn hex_fmt<T: fmt::Debug>(n: &T, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "0x{:02X?}", n)
    }

The resulting debug output would look something like this:

Foo {
    x: 42 things,
    z: 0xAB
}

Field attributes reference

Attributes within a section below are considered mutually exclusive.

Skip attributes


`skip`	Unconditionally skips a field.
`skip_if = path::to::function`	Skips a field if `path::to::function(&field)` returns `true`.

Format attributes


`format = "format string {}"`	Formats a field using a format string. Must contain a placeholder (`{}`) with modifiers of your choice.
`with = path::to::formatter`	Formats a field using `path::to::formatter`. The required signature is `fn(&T, &mut std::fmt::Formatter) -> std::fmt::Result` where `T` is a type compatible with the field's type (i.e. the function can be generic and coercions apply).

Dependencies

~1.2–1.6MB
~35K SLoC