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<main>
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<h2 id="cargo-工作空间"><a class="header" href="#cargo-工作空间">Cargo 工作空间</a></h2>
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<p><a href="https://github.com/rust-lang/book/blob/43b9ad334aaf7353e5708dba49f84f941b50ec4b/src/ch14-03-cargo-workspaces.md">ch14-03-cargo-workspaces.md</a></p>
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<p>第十二章中，我们构建了一个同时包含二进制 crate 和库 crate 的包。随着项目不断发展，你可能会发现库 crate 变得越来越大，并希望进一步将这个包拆分为多个库 crate。Cargo 提供了一项叫作<strong>工作空间</strong>（<em>workspace</em>）的功能，可以帮助管理多个彼此相关、并行开发的包。</p>
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<h3 id="创建工作空间"><a class="header" href="#创建工作空间">创建工作空间</a></h3>
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<p><strong>工作空间</strong>是一组共享同一个 <em>Cargo.lock</em> 和输出目录的包。让我们用工作空间创建一个项目，这里会使用简单代码，以便把注意力集中在工作空间的结构上。组织工作空间的方式有很多种，因此我们只展示一种常见方式。这个工作空间会包含一个二进制 crate 和两个库。二进制 crate 提供主要功能，并依赖这两个库。一个库提供 <code>add_one</code> 函数，另一个库提供 <code>add_two</code> 函数。这三个 crate 都属于同一个工作空间。我们先为工作空间创建一个新目录：</p>
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<pre><code class="language-console">$ mkdir add
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$ cd add
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</code></pre>
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<p>接下来，在 <em>add</em> 目录中创建 <em>Cargo.toml</em> 文件，用来配置整个工作空间。这个文件不会有 <code>[package]</code> 部分，而是会以 <code>[workspace]</code> 部分开头，这样我们就能向工作空间添加成员。我们还会把 <code>resolver</code> 的值设为 <code>"3"</code>，以便在工作空间中使用 Cargo 最新的依赖解析算法：</p>
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<p><span class="filename">文件名：Cargo.toml</span></p>
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<pre><code class="language-toml">[workspace]
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resolver = "3"
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</code></pre>
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<p>接下来，在 <em>add</em> 目录运行 <code>cargo new</code> 新建 <code>adder</code> 二进制 crate：</p>
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<pre><code class="language-console">$ cargo new adder
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Created binary (application) `adder` package
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Adding `adder` as member of workspace at `file:///projects/add`
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</code></pre>
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<p>在工作空间中运行 <code>cargo new</code> 时，新创建的包也会被自动加入工作空间 <em>Cargo.toml</em> 中 <code>[workspace]</code> 定义的 <code>members</code> 键，像这样：</p>
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<pre><code class="language-toml">[workspace]
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resolver = "3"
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members = ["adder"]
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</code></pre>
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|
|
<p>现在，我们可以运行 <code>cargo build</code> 来构建工作空间。你的 <em>add</em> 目录中的文件应如下所示：</p>
|
|
|
<pre><code class="language-text">├── Cargo.lock
|
|
|
├── Cargo.toml
|
|
|
├── adder
|
|
|
│ ├── Cargo.toml
|
|
|
│ └── src
|
|
|
│ └── main.rs
|
|
|
└── target
|
|
|
</code></pre>
|
|
|
<p>工作空间在顶层只有一个 <em>target</em> 目录，用来存放编译产物；<code>adder</code> 包不会有自己的 <em>target</em> 目录。即使我们在 <em>adder</em> 目录中运行 <code>cargo build</code>，编译产物也仍会放到 <em>add/target</em>，而不是 <em>add/adder/target</em>。Cargo 之所以这样组织工作空间中的 <em>target</em> 目录，是因为工作空间中的 crate 本来就是要彼此依赖的。如果每个 crate 都有各自的 <em>target</em> 目录，那么每个 crate 都不得不重新编译工作空间中的其他 crate，才能把产物放进自己的 <em>target</em> 目录。共享一个 <em>target</em> 目录可以避免不必要的重复构建。</p>
|
|
|
<h3 id="在工作空间中创建第二个包"><a class="header" href="#在工作空间中创建第二个包">在工作空间中创建第二个包</a></h3>
|
|
|
<p>接下来，让我们在工作空间中创建另一个成员包，并将其命名为 <code>add_one</code>。生成一个名为 <code>add_one</code> 的库 crate：</p>
|
|
|
<pre><code class="language-console">$ cargo new add_one --lib
|
|
|
Created library `add_one` package
|
|
|
Adding `add_one` as member of workspace at `file:///projects/add`
|
|
|
</code></pre>
|
|
|
<p>现在顶层的 <em>Cargo.toml</em> 的 <code>members</code> 列表将会包含 <em>add_one</em> 路径：</p>
|
|
|
<p><span class="filename">文件名：Cargo.toml</span></p>
|
|
|
<pre><code class="language-toml">[workspace]
|
|
|
resolver = "3"
|
|
|
members = ["adder", "add_one"]
|
|
|
</code></pre>
|
|
|
<p>现在 <em>add</em> 目录应该有如下目录和文件：</p>
|
|
|
<pre><code class="language-text">├── Cargo.lock
|
|
|
├── Cargo.toml
|
|
|
├── add_one
|
|
|
│ ├── Cargo.toml
|
|
|
│ └── src
|
|
|
│ └── lib.rs
|
|
|
├── adder
|
|
|
│ ├── Cargo.toml
|
|
|
│ └── src
|
|
|
│ └── main.rs
|
|
|
└── target
|
|
|
</code></pre>
|
|
|
<p>在 <em>add_one/src/lib.rs</em> 文件中，增加一个 <code>add_one</code> 函数：</p>
|
|
|
<p><span class="filename">文件名：add_one/src/lib.rs</span></p>
|
|
|
<pre><code class="language-rust noplayground">pub fn add_one(x: i32) -> i32 {
|
|
|
x + 1
|
|
|
}</code></pre>
|
|
|
<p>现在，我们可以让二进制包 <code>adder</code> 依赖包含库的 <code>add_one</code> 包了。首先，需要在 <em>adder/Cargo.toml</em> 中把 <code>add_one</code> 添加为一个路径依赖：</p>
|
|
|
<p><span class="filename">文件名：adder/Cargo.toml</span></p>
|
|
|
<pre><code class="language-toml">[dependencies]
|
|
|
add_one = { path = "../add_one" }
|
|
|
</code></pre>
|
|
|
<p>Cargo 并不会假定工作空间中的 crate 会彼此依赖，因此我们需要显式声明这些依赖关系。</p>
|
|
|
<p>接下来，让我们在 <code>adder</code> crate 中使用 <code>add_one</code> crate 里的 <code>add_one</code> 函数。打开 <em>adder/src/main.rs</em> 文件，并将 <code>main</code> 函数改为调用 <code>add_one</code>，如示例 14-7 所示。</p>
|
|
|
<p><span class="filename">文件名：adder/src/main.rs</span></p>
|
|
|
<pre><code class="language-rust ignore">fn main() {
|
|
|
let num = 10;
|
|
|
println!("Hello, world! {num} plus one is {}!", add_one::add_one(num));
|
|
|
}</code></pre>
|
|
|
<p><span class="caption">示例 14-7：在 <code>adder</code> crate 中使用 <code>add_one</code> 库 crate</span></p>
|
|
|
<p>在顶层 <em>add</em> 目录中运行 <code>cargo build</code> 来构建工作空间！</p>
|
|
|
<pre><code class="language-console">$ cargo build
|
|
|
Compiling add_one v0.1.0 (file:///projects/add/add_one)
|
|
|
Compiling adder v0.1.0 (file:///projects/add/adder)
|
|
|
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.22s
|
|
|
</code></pre>
|
|
|
<p>要从 <em>add</em> 目录运行这个二进制 crate，可以在 <code>cargo run</code> 时通过 <code>-p</code> 参数加上包名，指定要运行工作空间中的哪个包：</p>
|
|
|
<pre><code class="language-console">$ cargo run -p adder
|
|
|
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.00s
|
|
|
Running `target/debug/adder`
|
|
|
Hello, world! 10 plus one is 11!
|
|
|
</code></pre>
|
|
|
<p>这会运行 <em>adder/src/main.rs</em> 中的代码，其依赖 <code>add_one</code> crate。</p>
|
|
|
<h4 id="依赖外部包"><a class="header" href="#依赖外部包">依赖外部包</a></h4>
|
|
|
<p>注意，工作空间只在顶层有一个 <em>Cargo.lock</em> 文件，而不是让每个 crate 目录里都各自有一个 <em>Cargo.lock</em>。这能确保所有 crate 使用的都是同一个版本的依赖。如果我们把 <code>rand</code> 包同时加到 <em>adder/Cargo.toml</em> 和 <em>add_one/Cargo.toml</em> 中，Cargo 会把它们都解析为同一个 <code>rand</code> 版本，并把结果记录到唯一的 <em>Cargo.lock</em> 中。让工作空间中的所有 crate 使用相同依赖，意味着这些 crate 会始终彼此兼容。现在我们先把 <code>rand</code> crate 加到 <em>add_one/Cargo.toml</em> 的 <code>[dependencies]</code> 部分，以便能在 <code>add_one</code> crate 中使用它：</p>
|
|
|
<p><span class="filename">文件名：add_one/Cargo.toml</span></p>
|
|
|
<pre><code class="language-toml">[dependencies]
|
|
|
rand = "0.8.5"
|
|
|
</code></pre>
|
|
|
<p>现在我们可以在 <em>add_one/src/lib.rs</em> 中加入 <code>use rand;</code>，然后在 <em>add</em> 目录中运行 <code>cargo build</code> 来构建整个工作空间，这会引入并编译 <code>rand</code> crate。我们会得到一条警告，因为我们并没有实际使用引入到作用域中的 <code>rand</code>：</p>
|
|
|
<pre><code class="language-console">$ cargo build
|
|
|
Updating crates.io index
|
|
|
Downloaded rand v0.8.5
|
|
|
--snip--
|
|
|
Compiling rand v0.8.5
|
|
|
Compiling add_one v0.1.0 (file:///projects/add/add_one)
|
|
|
warning: unused import: `rand`
|
|
|
--> add_one/src/lib.rs:1:5
|
|
|
|
|
|
|
1 | use rand;
|
|
|
| ^^^^
|
|
|
|
|
|
|
= note: `#[warn(unused_imports)]` on by default
|
|
|
|
|
|
warning: `add_one` (lib) generated 1 warning (run `cargo fix --lib -p add_one` to apply 1 suggestion)
|
|
|
Compiling adder v0.1.0 (file:///projects/add/adder)
|
|
|
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.95s
|
|
|
</code></pre>
|
|
|
<p>顶层的 <em>Cargo.lock</em> 现在已经包含了 <code>add_one</code> 依赖 <code>rand</code> 的信息。不过，即使 <code>rand</code> 在工作空间的某处被使用，我们也不能直接在工作空间里的其他 crate 中使用它，除非也把 <code>rand</code> 加到它们各自的 <em>Cargo.toml</em> 中。例如，如果我们在 <code>adder</code> 包的 <em>adder/src/main.rs</em> 中加入 <code>use rand;</code>，就会得到一个错误：</p>
|
|
|
<pre><code class="language-console">$ cargo build
|
|
|
--snip--
|
|
|
Compiling adder v0.1.0 (file:///projects/add/adder)
|
|
|
error[E0432]: unresolved import `rand`
|
|
|
--> adder/src/main.rs:2:5
|
|
|
|
|
|
|
2 | use rand;
|
|
|
| ^^^^ no external crate `rand`
|
|
|
</code></pre>
|
|
|
<p>要修复这个错误，就编辑 <code>adder</code> 包的 <em>Cargo.toml</em> 文件，声明 <code>rand</code> 也是它的依赖。构建 <code>adder</code> 包时，会把 <code>rand</code> 加到 <em>Cargo.lock</em> 中 <code>adder</code> 的依赖列表里，但不会额外下载一份新的 <code>rand</code>。Cargo 会确保工作空间中每个使用 <code>rand</code> 的 crate 都使用同一个版本，只要它们声明的是彼此兼容的 <code>rand</code> 版本，这样既节省空间，也确保工作空间中的 crate 彼此兼容。</p>
|
|
|
<p>如果工作空间中的 crate 为同一个依赖指定了彼此不兼容的版本，Cargo 仍然会分别解析它们，但会尽量把版本数量控制得尽可能少。</p>
|
|
|
<h4 id="为工作空间增加测试"><a class="header" href="#为工作空间增加测试">为工作空间增加测试</a></h4>
|
|
|
<p>作为另一个改进，让我们为 <code>add_one</code> crate 中的 <code>add_one::add_one</code> 函数增加一个测试：</p>
|
|
|
<p><span class="filename">文件名：add_one/src/lib.rs</span></p>
|
|
|
<pre><code class="language-rust noplayground">pub fn add_one(x: i32) -> i32 {
|
|
|
x + 1
|
|
|
}
|
|
|
|
|
|
#[cfg(test)]
|
|
|
mod tests {
|
|
|
use super::*;
|
|
|
|
|
|
#[test]
|
|
|
fn it_works() {
|
|
|
assert_eq!(3, add_one(2));
|
|
|
}
|
|
|
}</code></pre>
|
|
|
<p>现在，在顶层 <em>add</em> 目录中运行 <code>cargo test</code>。在这种结构的工作空间里运行 <code>cargo test</code>，会执行工作空间中所有 crate 的测试：</p>
|
|
|
<pre><code class="language-console">$ cargo test
|
|
|
Compiling add_one v0.1.0 (file:///projects/add/add_one)
|
|
|
Compiling adder v0.1.0 (file:///projects/add/adder)
|
|
|
Finished `test` profile [unoptimized + debuginfo] target(s) in 0.20s
|
|
|
Running unittests src/lib.rs (target/debug/deps/add_one-93c49ee75dc46543)
|
|
|
|
|
|
running 1 test
|
|
|
test tests::it_works ... ok
|
|
|
|
|
|
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
|
|
|
|
|
|
Running unittests src/main.rs (target/debug/deps/adder-3a47283c568d2b6a)
|
|
|
|
|
|
running 0 tests
|
|
|
|
|
|
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
|
|
|
|
|
|
Doc-tests add_one
|
|
|
|
|
|
running 0 tests
|
|
|
|
|
|
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
|
|
|
</code></pre>
|
|
|
<p>输出的第一部分表明 <code>add_one</code> crate 中的 <code>it_works</code> 测试通过了。下一部分表明在 <code>adder</code> crate 中没有找到测试，最后一部分表明 <code>add_one</code> crate 中也没有文档测试。</p>
|
|
|
<p>你也可以选择只运行工作空间中某个特定 crate 的测试，只需在根目录中使用 <code>-p</code> 参数并指定想要测试的 crate 名称：</p>
|
|
|
<pre><code class="language-console">$ cargo test -p add_one
|
|
|
Finished `test` profile [unoptimized + debuginfo] target(s) in 0.00s
|
|
|
Running unittests src/lib.rs (target/debug/deps/add_one-93c49ee75dc46543)
|
|
|
|
|
|
running 1 test
|
|
|
test tests::it_works ... ok
|
|
|
|
|
|
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
|
|
|
|
|
|
Doc-tests add_one
|
|
|
|
|
|
running 0 tests
|
|
|
|
|
|
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
|
|
|
</code></pre>
|
|
|
<p>输出表明，<code>cargo test</code> 只运行了 <code>add_one</code> crate 的测试，而没有运行 <code>adder</code> crate 的测试。</p>
|
|
|
<p>如果你打算把工作空间中的 crate 发布到 <a href="https://crates.io/">crates.io</a> 上，那么工作空间中的每个 crate 都需要单独发布。和 <code>cargo test</code> 一样，你可以通过 <code>-p</code> 参数并指定要发布的 crate 名称，来发布工作空间中的某个特定 crate。</p>
|
|
|
<p>现在，试着仿照 <code>add_one</code> crate 的方式，把 <code>add_two</code> crate 也加入工作空间，作为额外练习吧！</p>
|
|
|
<p>随着项目规模增长，可以考虑使用工作空间：每个较小的组件都比一大块代码更容易理解。如果这些组件经常需要一起修改，那么把它们保留在同一个工作空间中，会更容易协调彼此的变更。</p>
|
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|
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