A Rust library for pretty ✨ printing using a document model. Automatically derive
Pretty
for structs, enums, and primitive types; vector and map types are also
supported by default; very similar to the derive(Debug)
macro, just prettier and more
configurable.
use pprint::{Doc, Printer, PRINTER};
let doc = Doc::from(vec![1, 2, 3])
.wrap("[", "]")
.join(", ");
print!("{}", PRINTER.pretty(doc));
// prints:
// [
// 1,
// 2,
// 3
// ]
The document model provides a rich set of building blocks:
- Primitive values like strings, numbers
- Containers like vectors, tuples, maps, sets
- Formatting like
concat
,join
,wrap
,group
- Indentation control with
indent
anddedent
- Conditional formatting with
if_break
- Line breaks like
hardline
,softline
The Printer
handles pretty printing a Doc
to a string with configurable options:
max_width
- maximum width of each lineindent
- number of spaces for each indentation levelbreak_long_text
- insert line breaks for long textuse_tabs
- use tabs instead of spaces for indentation
Half of the library's development time was spent on the derive macro, allowing for easy pretty printing of essentially any type. Here's a trivial example:
#[derive(Pretty)]
struct Point {
x: f64,
y: f64
}
let point = Point { x: 1.0, y: 2.0 };
print!("{}", Doc::from(point)); // prints "(x: 1, y: 2)"
Pretty
supports an additional attribute, pprint
, which is used to customize an
object's pretty printing definition. The following options are available:
- skip: bool: Skip this field - don't include it in the output
- indent: bool: Indent this field - add a newline and indent before and after
- rename: Option: Rename this field - use the given string as the field name
- getter: Option: Use the given function to get the value of this field
- verbose: bool: Verbose output - include field names in output
#[derive(Pretty)]
#[pprint(verbose)]
struct Point {
#[pprint(rename = "x-coordinate")]
x: f64,
#[pprint(rename = "y-coordinate")]
y: f64
#[pprint(skip)]
_skip_me: bool,
}
let point = Point { x: 1.0, y: 2.0, _skip_me: true };
print!("{}", Doc::from(point));
// prints:
// Point {
// x-coordinate: 1,
// y-coordinate: 2
// }
Structures can be arbitrarily nested, & c. & c. More involved examples can be found in the tests file.