Crate derive_debug
source ·Expand description
derive-debug
This crate implements a more customizable version of #[derive(Debug)]
.
Usage
The usage is very similar to #[derive(Debug)]
with a few extra customization options.
Deriving a struct
use derive_debug::Dbg;
#[derive(Dbg)]
struct Foo {
field_a: u32,
#[dbg(placeholder = "...")]
field_b: Vec<u32>, // will be printed as "field_b: ..."
#[dbg(skip)]
field_c: bool, // will be left out
#[dbg(alias = "my_string")]
field_d: u32, // will be printed as "my_string: 42"
#[dbg(fmt = "{:#06X}")]
field_e: u32, // will be printed with the specified format
}
Deriving an enum
use derive_debug::Dbg;
#[derive(Dbg)]
enum Foo {
VariantA(u32, u32, u32),
#[dbg(skip)]
VariantB{a: u32, b: bool}, // Will be printed as "VariantB"
// same options available as for struct fields
VariantC{a: u32, #[dbg(placeholder = "...")] b: bool}
}
Detailed options
Field Options
#[dbg(skip)]
completely omits a field in the output
use derive_debug::Dbg;
#[derive(Dbg)]
struct Foo {
field_a: bool,
#[dbg(skip)]
field_b: u32,
}
// Outputs: Foo { field_a: true }
#[dbg(placeholder = "xyz")]
will printxyz
instead of the actual contents of a field
use derive_debug::Dbg;
#[derive(Dbg)]
struct Foo {
field_a: bool,
#[dbg(placeholder = "...")]
field_b: u32,
}
// Outputs: Foo { field_a: true, field_b: ... }
#[dbg(alias = "some_alias")]
will printsome_alias
as field name instead of the real name
use derive_debug::Dbg;
#[derive(Dbg)]
struct Foo {
field_a: bool,
#[dbg(alias="not_field_b")]
field_b: u32,
}
// Outputs: Foo { field_a: true, not_field_b: 42 }
#[dbg(fmt = "{:#06X}")]
will print the field with the specified format
use derive_debug::Dbg;
#[derive(Dbg)]
struct Foo {
field_a: bool,
#[dbg(fmt = "{:#06X}")]
field_b: u32,
}
// Outputs: Foo { field_a: true, field_b: 0x002A }
#[dbg(formatter = "my_func")]
will print the field using the specified function.
The function has to return a type that can be formatted using “{}”
use derive_debug::Dbg;
#[derive(Dbg)]
struct Foo(u32, #[dbg(formatter = "fmt_not_zero")] u32);
fn fmt_not_zero(v: &u32) -> &'static str {
if *v == 0 {
"0"
} else {
"not 0"
}
}
// Outputs: Foo(42, not 0)
Enum Variant Options
#[dbg(skip)]
only prints the name of the variant and omits its contents
use derive_debug::Dbg;
#[derive(Dbg)]
enum Foo {
#[dbg(skip)]
SomeVariant{a: bool, b: u32},
}
// Outputs: SomeVariant
#[dbg(alias = "some_alias")]
will usesome_alias
as variant name instead of the real name
use derive_debug::Dbg;
#[derive(Dbg)]
enum Foo {
#[dbg(alias = "NotSomeVariant")]
SomeVariant{a: bool, b: u32},
}
// Outputs: NotSomeVariant { a: true, b: 42 }
struct Options
#[dbg(alias = "MyAlias")]
will useMyAlias
as struct name instead of the real name
use derive_debug::Dbg;
#[derive(Dbg)]
#[dbg(alias = "NotFoo")]
struct Foo {
field_a: bool,
field_b: u32,
}
// Outputs: NotFoo { field_a: true, not_field_b: 42 }