是否可以让货物始终显示警告？

Question

我使用的是watch与cargo中,为了快速查看编译时错误.但是,cargo build只会在第一次构建时显示错误.

$ cargo build
Compiling clayman v0.0.1
src/core_math/vector.rs:8:5: 13:6 warning: method is never used: `New`, #[warn(dead_code)] on by default
src/core_math/vector.rs:8     pub fn New(x: i32, y: i32) -> Vector {
src/core_math/vector.rs:9         Vector {
src/core_math/vector.rs:10             x: x,
src/core_math/vector.rs:11             y: y
src/core_math/vector.rs:12         }
src/core_math/vector.rs:13     }
src/core_math/vector.rs:8:5: 13:6 warning: method `New` should have a snake case name such as `new`, #[warn(non_snake_case)] on by default
src/core_math/vector.rs:8     pub fn New(x: i32, y: i32) -> Vector {
src/core_math/vector.rs:9         Vector {
src/core_math/vector.rs:10             x: x,
src/core_math/vector.rs:11             y: y
src/core_math/vector.rs:12         }
src/core_math/vector.rs:13     }
src/main.rs:28:9: 28:10 warning: unused variable: `v`, #[warn(unused_variables)] on by default
src/main.rs:28     let v: vector::Vector;
                   ^
$ cargo build
$

这意味着我只能在几秒钟之前看到警告,然后watch给我一个清晰的屏幕.

有没有办法cargo build让我总是给我警告？

Answer 1

从 Rust 1.40 开始，Cargo 将缓存编译器消息。这意味着即使代码不需要再次编译，之前的警告也会被打印出来。

锈1.40

% cargo build
   Compiling warnings v0.1.0 (/private/tmp/warnings)
warning: unused variable: `a`
 --> src/main.rs:2:9
  |
2 |     let a = 42;
  |         ^ help: consider prefixing with an underscore: `_a`
  |
  = note: `#[warn(unused_variables)]` on by default

    Finished dev [unoptimized + debuginfo] target(s) in 1.58s

% cargo build
warning: unused variable: `a`
 --> src/main.rs:2:9
  |
2 |     let a = 42;
  |         ^ help: consider prefixing with an underscore: `_a`
  |
  = note: `#[warn(unused_variables)]` on by default

    Finished dev [unoptimized + debuginfo] target(s) in 0.00s

锈1.39

% cargo build
   Compiling warnings v0.1.0 (/private/tmp/warnings)
warning: unused variable: `a`
 --> src/main.rs:2:9
  |
2 |     let a = 42;
  |         ^ help: consider prefixing with an underscore: `_a`
  |
  = note: `#[warn(unused_variables)]` on by default

    Finished dev [unoptimized + debuginfo] target(s) in 0.42s

% cargo build
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s

Answer 2

仅当 Rust 重新编译您的文件时才会出现警告；然而，它会尽可能多地缓存，如果某些内容没有改变，它会很高兴地跳过无用的编译。目前 Cargo 中没有强制重建的选项。

一个快速但肮脏的解决方案，但易于设置，是对touch源文件进行修改，以便 Cargo 相信它们已更改：

$ cd /path/to/project/root
$ ls
Cargo.lock Cargo.toml src        target
$ cargo build
     Compiling abc v0.1.0 (file:///private/tmp/b/abc)
  src/main.rs:2:9: 2:10 warning: unused variable: `x`, #[warn(unused_variables)] on by default
  src/main.rs:2     let x: u8 = 123;
                        ^
$ cargo build
$ touch $(find src)
$ cargo build
     Compiling abc v0.1.0 (file:///private/tmp/b/abc)
  src/main.rs:2:9: 2:10 warning: unused variable: `x`, #[warn(unused_variables)] on by default
  src/main.rs:2     let x: u8 = 123;
                        ^

另一个可能更好的解决方案是清除target包含二进制工件的目录，方法是cargo clean：

$ cargo build
   Compiling abc v0.1.0 (file:///private/tmp/b/abc)
src/main.rs:2:9: 2:10 warning: unused variable: `x`, #[warn(unused_variables)] on by default
src/main.rs:2     let x: u8 = 123;
                      ^
$ cargo build
$ cargo clean
$ cargo build
   Compiling abc v0.1.0 (file:///private/tmp/b/abc)
src/main.rs:2:9: 2:10 warning: unused variable: `x`, #[warn(unused_variables)] on by default
src/main.rs:2     let x: u8 = 123;
                      ^

它的优点是不会触发 Vim“文件已更改！” 警告，并且还可以在项目目录中的任何位置运行，而不仅仅是根目录。