How to Use the Command `cargo package` (with examples)

The cargo package command is a powerful tool for Rust developers, allowing them to assemble a local package into a distributable tarball (a .crate file). This command is beneficial for ensuring that a package is prepared correctly for distribution or publication. It acts similarly to running cargo publish --dry-run, but with more extensive options. Here, we will explore various use cases of the cargo package command and illustrate its functionality.

Use case 1: Perform Checks and Create a .crate File

Code:

cargo package

Motivation:

The primary motivation for using the cargo package command in this context is to prepare a Rust project for distribution without actually publishing it. This command performs a thorough check of the package, ensuring that all dependencies, metadata, and configurations are correctly set. Any mistakes or missing information are highlighted, providing the developer an opportunity to rectify them before proceeding to publish the package. This is particularly useful in a development workflow where verification of the package configuration is crucial before making it publicly available.

Explanation:

• cargo: This is the Rust package manager command-line tool that manages Rust projects.
• package: This specific command instructs cargo to assemble the current package into a .crate file and perform checks, analogous to a dry-run of the publishing process.

Example Output:

After executing the command, you might see an output similar to the following:

warning: description is missing in the package metadata
warning: package has unused dependencies: ...
    Packaging my_crate v0.1.0 (/path/to/my_crate)
    Verifying my_crate v0.1.0 (/path/to/my_crate)
    Creating ./target/package/my_crate-0.1.0.crate
    ```

In this output, warnings may be displayed if there are issues in the package metadata. The packaging process confirms the creation of a .crate file in the specified directory.

## Use case 2: Display What Files Would Be Included in the Tarball Without Actually Creating It

Code:

```shell
cargo package --list

Motivation:

Sometimes, a developer wants to verify which files from a project will be included in the distributable crate file without generating it. This is where the cargo package --list option proves invaluable. It offers a comprehensive list of all the files that are part of the package, giving the developer insight into the contents of the future .crate file. This is especially beneficial in ensuring that no unnecessary files are included or critical files are accidentally excluded.

Explanation:

• cargo: As before, this is the Rust package manager command-line tool.
• package: This command prepares the package and checks configurations.
• --list: This option, when appended, changes the behavior of the cargo package command to list the files that would be included in the package. It doesn’t create the actual package but provides details about its potential contents.

Example Output:

Executing this command might yield a result such as:

Cargo.toml
src/lib.rs
README.md
LICENSE

The output lists the files that would be packaged into the tarball if the command to create it were executed. This allows for preliminary verification and adjustments as needed.

Conclusion:

The cargo package command is an essential tool for Rust developers, providing mechanisms to prepare, verify, and inspect Rust packages before they are published. Each use case discussed here serves different purposes but ultimately facilitates a more robust and error-free publishing process. Whether you aim to perform thorough checks with cargo package or simply wish to review the package contents with cargo package --list, these functionalities help maintain the integrity and accuracy of your Rust package distributions.