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<ol class="chapter"><li class="affix"><a href="foreword.html">Foreword</a></li><li class="affix"><a href="ch00-00-introduction.html">Introduction</a></li><li><a href="ch01-00-getting-started.html"><strong aria-hidden="true">1.</strong> Getting Started</a></li><li><ol class="section"><li><a href="ch01-01-installation.html"><strong aria-hidden="true">1.1.</strong> Installation</a></li><li><a href="ch01-02-hello-world.html"><strong aria-hidden="true">1.2.</strong> Hello, World!</a></li><li><a href="ch01-03-hello-cargo.html"><strong aria-hidden="true">1.3.</strong> Hello, Cargo!</a></li></ol></li><li><a href="ch02-00-guessing-game-tutorial.html"><strong aria-hidden="true">2.</strong> Programming a Guessing Game</a></li><li><a href="ch03-00-common-programming-concepts.html"><strong aria-hidden="true">3.</strong> Common Programming Concepts</a></li><li><ol class="section"><li><a href="ch03-01-variables-and-mutability.html"><strong aria-hidden="true">3.1.</strong> Variables and Mutability</a></li><li><a href="ch03-02-data-types.html"><strong aria-hidden="true">3.2.</strong> Data Types</a></li><li><a href="ch03-03-how-functions-work.html"><strong aria-hidden="true">3.3.</strong> How Functions Work</a></li><li><a href="ch03-04-comments.html"><strong aria-hidden="true">3.4.</strong> Comments</a></li><li><a href="ch03-05-control-flow.html"><strong aria-hidden="true">3.5.</strong> Control Flow</a></li></ol></li><li><a href="ch04-00-understanding-ownership.html"><strong aria-hidden="true">4.</strong> Understanding Ownership</a></li><li><ol class="section"><li><a href="ch04-01-what-is-ownership.html"><strong aria-hidden="true">4.1.</strong> What is Ownership?</a></li><li><a href="ch04-02-references-and-borrowing.html"><strong aria-hidden="true">4.2.</strong> References & Borrowing</a></li><li><a href="ch04-03-slices.html"><strong aria-hidden="true">4.3.</strong> Slices</a></li></ol></li><li><a href="ch05-00-structs.html"><strong aria-hidden="true">5.</strong> Using Structs to Structure Related Data</a></li><li><ol class="section"><li><a href="ch05-01-defining-structs.html"><strong aria-hidden="true">5.1.</strong> Defining and Instantiating Structs</a></li><li><a href="ch05-02-example-structs.html"><strong aria-hidden="true">5.2.</strong> An Example Program Using Structs</a></li><li><a href="ch05-03-method-syntax.html"><strong aria-hidden="true">5.3.</strong> Method Syntax</a></li></ol></li><li><a href="ch06-00-enums.html"><strong aria-hidden="true">6.</strong> Enums and Pattern Matching</a></li><li><ol class="section"><li><a href="ch06-01-defining-an-enum.html"><strong aria-hidden="true">6.1.</strong> Defining an Enum</a></li><li><a href="ch06-02-match.html"><strong aria-hidden="true">6.2.</strong> The match Control Flow Operator</a></li><li><a href="ch06-03-if-let.html"><strong aria-hidden="true">6.3.</strong> Concise Control Flow with if let</a></li></ol></li><li><a href="ch07-00-modules.html"><strong aria-hidden="true">7.</strong> Modules</a></li><li><ol class="section"><li><a href="ch07-01-mod-and-the-filesystem.html"><strong aria-hidden="true">7.1.</strong> mod and the Filesystem</a></li><li><a href="ch07-02-controlling-visibility-with-pub.html"><strong aria-hidden="true">7.2.</strong> Controlling Visibility with pub</a></li><li><a href="ch07-03-importing-names-with-use.html"><strong aria-hidden="true">7.3.</strong> Referring to Names in Different Modules</a></li></ol></li><li><a href="ch08-00-common-collections.html"><strong aria-hidden="true">8.</strong> Common Collections</a></li><li><ol class="section"><li><a href="ch08-01-vectors.html"><strong aria-hidden="true">8.1.</strong> Vectors</a></li><li><a href="ch08-02-strings.html"><strong aria-hidden="true">8.2.</strong> Strings</a></li><li><a href="ch08-03-hash-maps.html"><strong aria-hidden="true">8.3.</strong> Hash Maps</a></li></ol></li><li><a href="ch09-00-error-handling.html"><strong aria-hidden="true">9.</strong> Error Handling</a></li><li><ol class="section"><li><a href="ch09-01-unrecoverable-errors-with-panic.html"><strong aria-hidden="true">9.1.</strong> Unrecoverable Errors with panic!</a></li><li><a href="ch09-02-recoverable-errors-with-result.html"><strong aria-hidden="true">9.2.</strong> Recoverable Errors with Result</a></li><li><a href="ch09-03-to-panic-or-not-to-panic.html"><strong aria-hidden="true">9.3.</strong> To panic! or Not To panic!</a></li></ol></li><li><a href="ch10-00-generics.html"><strong aria-hidden="true">10.</strong> Generic Types, Traits, and Lifetimes</a></li><li><ol class="section"><li><a href="ch10-01-syntax.html"><strong aria-hidden="true">10.1.</strong> Generic Data Types</a></li><li><a href="ch10-02-traits.html"><strong aria-hidden="true">10.2.</strong> Traits: Defining Shared Behavior</a></li><li><a href="ch10-03-lifetime-syntax.html"><strong aria-hidden="true">10.3.</strong> Validating References with Lifetimes</a></li></ol></li><li><a href="ch11-00-testing.html"><strong aria-hidden="true">11.</strong> Testing</a></li><li><ol class="section"><li><a href="ch11-01-writing-tests.html"><strong aria-hidden="true">11.1.</strong> Writing tests</a></li><li><a href="ch11-02-running-tests.html"><strong aria-hidden="true">11.2.</strong> Running tests</a></li><li><a href="ch11-03-test-organization.html"><strong aria-hidden="true">11.3.</strong> Test Organization</a></li></ol></li><li><a href="ch12-00-an-io-project.html"><strong aria-hidden="true">12.</strong> An I/O Project: Building a Command Line Program</a></li><li><ol class="section"><li><a href="ch12-01-accepting-command-line-arguments.html"><strong aria-hidden="true">12.1.</strong> Accepting Command Line Arguments</a></li><li><a href="ch12-02-reading-a-file.html"><strong aria-hidden="true">12.2.</strong> Reading a File</a></li><li><a href="ch12-03-improving-error-handling-and-modularity.html"><strong aria-hidden="true">12.3.</strong> Refactoring to Improve Modularity and Error Handling</a></li><li><a href="ch12-04-testing-the-librarys-functionality.html"><strong aria-hidden="true">12.4.</strong> Developing the Library’s Functionality with Test Driven Development</a></li><li><a href="ch12-05-working-with-environment-variables.html"><strong aria-hidden="true">12.5.</strong> Working with Environment Variables</a></li><li><a href="ch12-06-writing-to-stderr-instead-of-stdout.html"><strong aria-hidden="true">12.6.</strong> Writing Error Messages to Standard Error Instead of Standard Output</a></li></ol></li><li><a href="ch13-00-functional-features.html"><strong aria-hidden="true">13.</strong> Functional Language Features: Iterators and Closures</a></li><li><ol class="section"><li><a href="ch13-01-closures.html"><strong aria-hidden="true">13.1.</strong> Closures: Anonymous Functions that Can Capture Their Environment</a></li><li><a href="ch13-02-iterators.html"><strong aria-hidden="true">13.2.</strong> Processing a Series of Items with Iterators</a></li><li><a href="ch13-03-improving-our-io-project.html"><strong aria-hidden="true">13.3.</strong> Improving Our I/O Project</a></li><li><a href="ch13-04-performance.html"><strong aria-hidden="true">13.4.</strong> Comparing Performance: Loops vs. Iterators</a></li></ol></li><li><a href="ch14-00-more-about-cargo.html"><strong aria-hidden="true">14.</strong> More about Cargo and Crates.io</a></li><li><ol class="section"><li><a href="ch14-01-release-profiles.html"><strong aria-hidden="true">14.1.</strong> Customizing Builds with Release Profiles</a></li><li><a href="ch14-02-publishing-to-crates-io.html"><strong aria-hidden="true">14.2.</strong> Publishing a Crate to Crates.io</a></li><li><a href="ch14-03-cargo-workspaces.html" class="active"><strong aria-hidden="true">14.3.</strong> Cargo Workspaces</a></li><li><a href="ch14-04-installing-binaries.html"><strong aria-hidden="true">14.4.</strong> Installing Binaries from Crates.io with cargo install</a></li><li><a href="ch14-05-extending-cargo.html"><strong aria-hidden="true">14.5.</strong> Extending Cargo with Custom Commands</a></li></ol></li><li><a href="ch15-00-smart-pointers.html"><strong aria-hidden="true">15.</strong> Smart Pointers</a></li><li><ol class="section"><li><a href="ch15-01-box.html"><strong aria-hidden="true">15.1.</strong> Box<T> Points to Data on the Heap and Has a Known Size</a></li><li><a href="ch15-02-deref.html"><strong aria-hidden="true">15.2.</strong> The Deref Trait Allows Access to the Data Through a Reference</a></li><li><a href="ch15-03-drop.html"><strong aria-hidden="true">15.3.</strong> The Drop Trait Runs Code on Cleanup</a></li><li><a href="ch15-04-rc.html"><strong aria-hidden="true">15.4.</strong> Rc<T>, the Reference Counted Smart Pointer</a></li><li><a href="ch15-05-interior-mutability.html"><strong aria-hidden="true">15.5.</strong> RefCell<T> and the Interior Mutability Pattern</a></li><li><a href="ch15-06-reference-cycles.html"><strong aria-hidden="true">15.6.</strong> Creating Reference Cycles and Leaking Memory is Safe</a></li></ol></li><li><a href="ch16-00-concurrency.html"><strong aria-hidden="true">16.</strong> Fearless Concurrency</a></li><li><ol class="section"><li><a href="ch16-01-threads.html"><strong aria-hidden="true">16.1.</strong> Threads</a></li><li><a href="ch16-02-message-passing.html"><strong aria-hidden="true">16.2.</strong> Message Passing</a></li><li><a href="ch16-03-shared-state.html"><strong aria-hidden="true">16.3.</strong> Shared State</a></li><li><a href="ch16-04-extensible-concurrency-sync-and-send.html"><strong aria-hidden="true">16.4.</strong> Extensible Concurrency: Sync and Send</a></li></ol></li><li><a href="ch17-00-oop.html"><strong aria-hidden="true">17.</strong> Object Oriented Programming Features of Rust</a></li><li><ol class="section"><li><a href="ch17-01-what-is-oo.html"><strong aria-hidden="true">17.1.</strong> Characteristics of Object-Oriented Languages</a></li><li><a href="ch17-02-trait-objects.html"><strong aria-hidden="true">17.2.</strong> Using Trait Objects that Allow for Values of Different Types</a></li><li><a href="ch17-03-oo-design-patterns.html"><strong aria-hidden="true">17.3.</strong> Implementing an Object-Oriented Design Pattern</a></li></ol></li><li><a href="ch18-00-patterns.html"><strong aria-hidden="true">18.</strong> Patterns Match the Structure of Values</a></li><li><ol class="section"><li><a href="ch18-01-all-the-places-for-patterns.html"><strong aria-hidden="true">18.1.</strong> All the Places Patterns May be Used</a></li><li><a href="ch18-02-refutability.html"><strong aria-hidden="true">18.2.</strong> Refutability: Whether a Pattern Might Fail to Match</a></li><li><a href="ch18-03-pattern-syntax.html"><strong aria-hidden="true">18.3.</strong> All the Pattern Syntax</a></li></ol></li><li><a href="ch19-00-advanced-features.html"><strong aria-hidden="true">19.</strong> Advanced Features</a></li><li><ol class="section"><li><a href="ch19-01-unsafe-rust.html"><strong aria-hidden="true">19.1.</strong> Unsafe Rust</a></li><li><a href="ch19-02-advanced-lifetimes.html"><strong aria-hidden="true">19.2.</strong> Advanced Lifetimes</a></li><li><a href="ch19-03-advanced-traits.html"><strong aria-hidden="true">19.3.</strong> Advanced Traits</a></li><li><a href="ch19-04-advanced-types.html"><strong aria-hidden="true">19.4.</strong> Advanced Types</a></li><li><a href="ch19-05-advanced-functions-and-closures.html"><strong aria-hidden="true">19.5.</strong> Advanced Functions & Closures</a></li></ol></li><li><a href="ch20-00-final-project-a-web-server.html"><strong aria-hidden="true">20.</strong> Final Project: Building a Multithreaded Web Server</a></li><li><ol class="section"><li><a href="ch20-01-single-threaded.html"><strong aria-hidden="true">20.1.</strong> A Single Threaded Web Server</a></li><li><a href="ch20-02-multithreaded.html"><strong aria-hidden="true">20.2.</strong> Turning our Single Threaded Server into a Multithreaded Server</a></li><li><a href="ch20-03-graceful-shutdown-and-cleanup.html"><strong aria-hidden="true">20.3.</strong> Graceful Shutdown and Cleanup</a></li></ol></li><li><a href="appendix-00.html"><strong aria-hidden="true">21.</strong> Appendix</a></li><li><ol class="section"><li><a href="appendix-01-keywords.html"><strong aria-hidden="true">21.1.</strong> A - Keywords</a></li><li><a href="appendix-02-operators.html"><strong aria-hidden="true">21.2.</strong> B - Operators and Symbols</a></li><li><a href="appendix-03-derivable-traits.html"><strong aria-hidden="true">21.3.</strong> C - Derivable Traits</a></li><li><a href="appendix-04-macros.html"><strong aria-hidden="true">21.4.</strong> D - Macros</a></li><li><a href="appendix-05-translation.html"><strong aria-hidden="true">21.5.</strong> E - Translations</a></li><li><a href="appendix-06-newest-features.html"><strong aria-hidden="true">21.6.</strong> F - Newest Features</a></li><li><a href="appendix-07-nightly-rust.html"><strong aria-hidden="true">21.7.</strong> G - How Rust is Made and “Nightly Rust”</a></li></ol></li></ol>
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<a class="header" href="ch14-03-cargo-workspaces.html#cargo-workspaces" id="cargo-workspaces"><h2>Cargo Workspaces</h2></a>
<p>In Chapter 12, we built a package that included a binary crate and a library
crate. As your project develops, you might find that the library crate
continues to get bigger and you want to split up your package further into
multiple library crates. In this situation, Cargo offers a feature called
<em>workspaces</em> that can help manage multiple related packages that are developed
in tandem.</p>
<a class="header" href="ch14-03-cargo-workspaces.html#creating-a-workspace" id="creating-a-workspace"><h3>Creating a Workspace</h3></a>
<p>A <em>workspace</em> is a set of packages that share the same <em>Cargo.lock</em> and output
directory. Let’s make a project using a workspace—we’ll use trivial code so we
can concentrate on the structure of the workspace. There are multiple ways to
structure a workspace; we’re going to show one common way. We’ll have a
workspace containing a binary and two libraries. The binary, which will provide
the main functionality, will depend on the two libraries. One library will
provide an <code>add_one</code> function, and a second library an <code>add_two</code> function.
These three crates will be part of the same workspace. We’ll start by creating
a new directory for the workspace:</p>
<pre><code class="language-text">$ mkdir add
$ cd add
</code></pre>
<p>Next, in the <em>add</em> directory, we create the <em>Cargo.toml</em> file that will
configure the entire workspace. This file won’t have a <code>[package]</code> section or
the metadata we’ve seen in other <em>Cargo.toml</em> files. Instead, it will start
with a <code>[workspace]</code> section that will allow us to add members to the workspace
by specifying the path to our binary crate; in this case, that path is <em>adder</em>:</p>
<p><span class="filename">Filename: Cargo.toml</span></p>
<pre><code class="language-toml">[workspace]
members = [
"adder",
]
</code></pre>
<p>Next, we’ll create the <code>adder</code> binary crate by running <code>cargo new</code> within the
<em>add</em> directory:</p>
<pre><code class="language-text">$ cargo new --bin adder
Created binary (application) `adder` project
</code></pre>
<p>At this point, we can build the workspace by running <code>cargo build</code>. The files
in your <em>add</em> directory should look like this:</p>
<pre><code class="language-text">├── Cargo.lock
├── Cargo.toml
├── adder
│ ├── Cargo.toml
│ └── src
│ └── main.rs
└── target
</code></pre>
<p>The workspace has one <em>target</em> directory at the top level for the compiled
artifacts to be placed into; the <code>adder</code> crate doesn’t have its own <em>target</em>
directory. Even if we were to run <code>cargo build</code> from inside the <em>adder</em>
directory, the compiled artifacts would still end up in <em>add/target</em> rather
than <em>add/adder/target</em>. Cargo structures the <em>target</em> directory in a workspace
like this because the crates in a workspace are meant to depend on each other.
If each crate had its own <em>target</em> directory, each crate would have to
recompile each of the other crates in the workspace to have the artifacts in
its own <em>target</em> directory. By sharing one <em>target</em> directory, the crates can
avoid unnecessary rebuilding.</p>
<a class="header" href="ch14-03-cargo-workspaces.html#creating-the-second-crate-in-the-workspace" id="creating-the-second-crate-in-the-workspace"><h3>Creating the Second Crate in the Workspace</h3></a>
<p>Next, let’s create another member crate in the workspace and call it <code>add-one</code>.
Change the top-level <em>Cargo.toml</em> to specify the <em>add-one</em> path in the
<code>members</code> list:</p>
<p><span class="filename">Filename: Cargo.toml</span></p>
<pre><code class="language-toml">[workspace]
members = [
"adder",
"add-one",
]
</code></pre>
<p>Then generate a new library crate named <code>add-one</code>:</p>
<pre><code class="language-text">$ cargo new add-one
Created library `add-one` project
</code></pre>
<p>Your <em>add</em> directory should now have these directories and files:</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>In the <em>add-one/src/lib.rs</em> file, let’s add an <code>add_one</code> function:</p>
<p><span class="filename">Filename: add-one/src/lib.rs</span></p>
<pre><pre class="playpen"><code class="language-rust">
# #![allow(unused_variables)]
#fn main() {
pub fn add_one(x: i32) -> i32 {
x + 1
}
#}</code></pre></pre>
<p>Now that we have a library crate in the workspace, we can have the binary crate
<code>adder</code> depend on the library crate <code>add-one</code>. First, we’ll need to add a path
dependency on <code>add-one</code> to <em>adder/Cargo.toml</em>.</p>
<p><span class="filename">Filename: adder/Cargo.toml</span></p>
<pre><code class="language-toml">[dependencies]
add-one = { path = "../add-one" }
</code></pre>
<p>Cargo doesn’t assume that crates in a workspace will depend on each other, so
we need to be explicit about the dependency relationships between the crates.</p>
<p>Next, let’s use the <code>add_one</code> function from the <code>add-one</code> crate in the <code>adder</code>
crate. Open the <em>adder/src/main.rs</em> file and add an <code>extern crate</code> line at
the top to bring the new <code>add-one</code> library crate into scope. Then change the
<code>main</code> function to call the <code>add_one</code> function, as in Listing 14-7:</p>
<p><span class="filename">Filename: adder/src/main.rs</span></p>
<pre><code class="language-rust ignore">extern crate add_one;
fn main() {
let num = 10;
println!("Hello, world! {} plus one is {}!", num, add_one::add_one(num));
}
</code></pre>
<p><span class="caption">Listing 14-7: Using the <code>add-one</code> library crate from the
<code>adder</code> crate</span></p>
<p>Let’s build the workspace by running <code>cargo build</code> in the top-level <em>add</em>
directory!</p>
<pre><code class="language-text">$ cargo build
Compiling add-one v0.1.0 (file:///projects/add/add-one)
Compiling adder v0.1.0 (file:///projects/add/adder)
Finished dev [unoptimized + debuginfo] target(s) in 0.68 secs
</code></pre>
<p>To run the binary crate from the <em>add</em> directory, we need to specify which
package in the workspace we want to use by using the <code>-p</code> argument and the
package name with <code>cargo run</code>:</p>
<pre><code class="language-text">$ cargo run -p adder
Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
Running `target/debug/adder`
Hello, world! 10 plus one is 11!
</code></pre>
<p>This runs the code in <em>adder/src/main.rs</em>, which depends on the <code>add-one</code> crate.</p>
<a class="header" href="ch14-03-cargo-workspaces.html#depending-on-an-external-crate-in-a-workspace" id="depending-on-an-external-crate-in-a-workspace"><h4>Depending on an External Crate in a Workspace</h4></a>
<p>Notice that the workspace has only one <em>Cargo.lock</em> file at the top level of
the workspace rather than having a <em>Cargo.lock</em> in each crate’s directory. This
ensures that all crates are using the same version of all dependencies. If we
add the <code>rand</code> crate to the <em>adder/Cargo.toml</em> and <em>add-one/Cargo.toml</em>
files, Cargo will resolve both of those to one version of <code>rand</code> and record
that in the one <em>Cargo.lock</em>. Making all crates in the workspace use the same
dependencies means the crates in the workspace will always be compatible with
each other. Let’s add the <code>rand</code> crate to the <code>[dependencies]</code> section in the
<em>add-one/Cargo.toml</em> file to be able to use the <code>rand</code> crate in the <code>add-one</code>
crate:</p>
<p><span class="filename">Filename: add-one/Cargo.toml</span></p>
<pre><code class="language-toml">[dependencies]
rand = "0.3.14"
</code></pre>
<p>We can now add <code>extern crate rand;</code> to the <em>add-one/src/lib.rs</em> file, and
building the whole workspace by running <code>cargo build</code> in the <em>add</em> directory
will bring in and compile the <code>rand</code> crate:</p>
<pre><code class="language-text">$ cargo build
Updating registry `https://github.com/rust-lang/crates.io-index`
Downloading rand v0.3.14
--snip--
Compiling rand v0.3.14
Compiling add-one v0.1.0 (file:///projects/add/add-one)
Compiling adder v0.1.0 (file:///projects/add/adder)
Finished dev [unoptimized + debuginfo] target(s) in 10.18 secs
</code></pre>
<p>The top-level <em>Cargo.lock</em> now contains information about the dependency of
<code>add-one</code> on <code>rand</code>. However, even though <code>rand</code> is used somewhere in the
workspace, we can’t use it in other crates in the workspace unless we add
<code>rand</code> to their <em>Cargo.toml</em> files as well. For example, if we add <code>extern crate rand;</code> to the <em>adder/src/main.rs</em> file for the <code>adder</code> crate, we’ll get
an error:</p>
<pre><code class="language-text">$ cargo build
Compiling adder v0.1.0 (file:///projects/add/adder)
error: use of unstable library feature 'rand': use `rand` from crates.io (see
issue #27703)
--> adder/src/main.rs:1:1
|
1 | extern crate rand;
</code></pre>
<p>To fix this, edit the <em>Cargo.toml</em> file for the <code>adder</code> crate and indicate that
<code>rand</code> is a dependency for that crate as well. Building the <code>adder</code> crate will
add <code>rand</code> to the list of dependencies for <code>adder</code> in <em>Cargo.lock</em>, but no
additional copies of <code>rand</code> will be downloaded. Cargo has ensured that every
crate in the workspace using the <code>rand</code> crate will be using the same version.
Using the same version of <code>rand</code> across the workspace saves space because we
won’t have multiple copies and ensures that the crates in the workspace will be
compatible with each other.</p>
<a class="header" href="ch14-03-cargo-workspaces.html#adding-a-test-to-a-workspace" id="adding-a-test-to-a-workspace"><h4>Adding a Test to a Workspace</h4></a>
<p>For another enhancement, let’s add a test of the <code>add_one::add_one</code> function
within the <code>add_one</code> crate:</p>
<p><span class="filename">Filename: add-one/src/lib.rs</span></p>
<pre><pre class="playpen"><code class="language-rust">
# #![allow(unused_variables)]
#fn main() {
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></pre>
<p>Now run <code>cargo test</code> in the top-level <em>add</em> directory:</p>
<pre><code class="language-text">$ cargo test
Compiling add-one v0.1.0 (file:///projects/add/add-one)
Compiling adder v0.1.0 (file:///projects/add/adder)
Finished dev [unoptimized + debuginfo] target(s) in 0.27 secs
Running target/debug/deps/add_one-f0253159197f7841
running 1 test
test tests::it_works ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Running target/debug/deps/adder-f88af9d2cc175a5e
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Doc-tests add-one
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
</code></pre>
<p>The first section of the output shows that the <code>it_works</code> test in the <code>add-one</code>
crate passed. The next section shows that zero tests were found in the <code>adder</code>
crate, and then the last section shows zero documentation tests were found in
the <code>add-one</code> crate. Running <code>cargo test</code> in a workspace structured like this
one will run the tests for all the crates in the workspace.</p>
<p>We can also run tests for one particular crate in a workspace from the
top-level directory by using the <code>-p</code> flag and specifying the name of the crate
we want to test:</p>
<pre><code class="language-text">$ cargo test -p add-one
Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
Running target/debug/deps/add_one-b3235fea9a156f74
running 1 test
test tests::it_works ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Doc-tests add-one
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
</code></pre>
<p>This output shows <code>cargo test</code> only ran the tests for the <code>add-one</code> crate and
didn’t run the <code>adder</code> crate tests.</p>
<p>If you publish the crates in the workspace to <em>https://crates.io/</em>, each crate
in the workspace will need to be published separately. The <code>cargo publish</code>
command does not have an <code>--all</code> flag or a <code>-p</code> flag, so you must change to
each crate’s directory and run <code>cargo publish</code> on each crate in the workspace
to publish the crates.</p>
<p>For additional practice, add an <code>add-two</code> crate to this workspace in a similar
way as the <code>add-one</code> crate!</p>
<p>As your project grows, consider using a workspace: it’s easier to understand
smaller, individual components than one big blob of code. Furthermore, keeping
the crates in a workspace can make coordination between them easier if they are
often changed at the same time.</p>
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