Indented document literals for Rust
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Indented Documents (indoc)

Build Status Latest Version

This crate provides a procedural macro for indented string literals. The indoc!() macro takes a multiline string literal and un-indents it so the leftmost non-space character is in the first column.

indoc = "0.3"

Release notes are available under GitHub releases.

Using Indoc

extern crate indoc;
use indoc::indoc;

fn main() {
    let testing = indoc!("
        def hello():
            print('Hello, world!')

    let expected = "def hello():\n    print('Hello, world!')\n\nhello()\n";
    assert_eq!(testing, expected);

Indoc also works with raw string literals:

extern crate indoc;
use indoc::indoc;

fn main() {
    let testing = indoc!(r#"
        def hello():
            print("Hello, world!")

    let expected = "def hello():\n    print(\"Hello, world!\")\n\nhello()\n";
    assert_eq!(testing, expected);

And byte string literals:

extern crate indoc;
use indoc::indoc;

fn main() {
    let testing = indoc!(b"
        def hello():
            print('Hello, world!')

    let expected = b"def hello():\n    print('Hello, world!')\n\nhello()\n";
    assert_eq!(testing[..], expected[..]);


The following rules characterize the behavior of the indoc!() macro:

  1. Count the leading spaces of each line, ignoring the first line and any lines that are empty or contain spaces only.
  2. Take the minimum.
  3. If the first line is empty i.e. the string begins with a newline, remove the first line.
  4. Remove the computed number of spaces from the beginning of each line.

This means there are a few equivalent ways to format the same string, so choose one you like. All of the following result in the string "line one\nline two\n":

indoc!("            /      indoc!(             /      indoc!("line one
   line one        /         "line one        /               line two
   line two       /           line two       /                ")
   ")            /            ")            /


Indoc's indentation logic is available in the unindent crate. This may be useful for processing strings that are not statically known at compile time.

The crate exposes two functions:

  • unindent(&str) -> String
  • unindent_bytes(&[u8]) -> Vec<u8>
extern crate unindent;
use unindent::unindent;

fn main() {
    let indented = "
            line one
            line two";
    assert_eq!("line one\nline two", unindent(indented));


Licensed under either of

at your option.


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