缩进文档 (indoc)

此crate提供了一个用于缩进字符串字面量的过程宏。宏 indoc!() 在编译时将多行字符串字面量取消缩进，使最左侧的非空字符位于第一列。

[dependencies]
indoc = "2"

编译器要求：rustc 1.56 或更高版本。

使用 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 也可以与原始字符串字面量一起使用

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);
}

以及字节字符串字面量

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[..]);
}

格式化宏

indoc crate导出五个额外的宏，方便地替换标准库的格式化宏

• formatdoc!($fmt, ...) — 等同于 format!(indoc!($fmt), ...)
• printdoc!($fmt, ...) — 等同于 print!(indoc!($fmt), ...)
• eprintdoc!($fmt, ...) —— 等价于 eprint!(indoc!($fmt), ...)
• writedoc!($dest, $fmt, ...) —— 等价于 write!($dest, indoc!($fmt), ...)
• concatdoc!(...) —— 等价于 concat!(...)，每个字符串字面量都被 indoc! 包裹

use indoc::{concatdoc, printdoc};

const HELP: &str = concatdoc! {"
    Usage: ", env!("CARGO_BIN_NAME"), " [options]

    Options:
        -h, --help
"};

fn main() {
    printdoc! {"
        GET {url}
        Accept: {mime}
        ",
        url = "http://127.0.0.1:8080",
        mime = "application/json",
    }
}

说明

以下规则定义了 indoc!() 宏的行为

use unindent::unindent;

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