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#27 in Rust patterns

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Used in 120 crates (79 directly)

MIT/Apache

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Indented Documents (indoc)

github crates.io docs.rs build status

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

[dependencies]
indoc = "1.0"

Compiler requirement: rustc 1.45 or greater.


Using indoc

use indoc::indoc;

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

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

Indoc also works with raw string literals:

use indoc::indoc;

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

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

And byte string literals:

use indoc::indoc;

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

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

Formatting macros

The indoc crate exports four additional macros to substitute conveniently for the standard library's formatting macros:

  • formatdoc!($fmt, ...) — equivalent to format!(indoc!($fmt), ...)
  • printdoc!($fmt, ...) — equivalent to print!(indoc!($fmt), ...)
  • eprintdoc!($fmt, ...) — equivalent to eprint!(indoc!($fmt), ...)
  • writedoc!($dest, $fmt, ...) — equivalent to write!($dest, indoc!($fmt), ...)
use indoc::printdoc;

fn main() {
    printdoc! {"
        GET {url}
        Accept: {mime}
        ",
        url = "http://localhost:8080",
        mime = "application/json",
    }
}

Explanation

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.

Unindent

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>
use unindent::unindent;

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

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 this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Dependencies