cargo-expand を Homebrew, apk, Nix, pacman でインストール

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コマンドとエイリアス

• cargo-expand

プロジェクトの歴史

The GitHub repository and crates.io crate were both created in June 2016. The README describes cargo-expand as a wrapper around `cargo rustc --profile=check -- -Zunpretty=expanded`, printing the result of macro expansion and derive expansion for the current crate.

The project was created by David Tolnay, whose broader Rust tooling ecosystem includes heavily used macro and parsing crates. cargo-expand became especially useful as Rust derive macros, procedural macros, and macro-heavy libraries became common in everyday Rust code.

The README includes an explicit disclaimer that macro expansion to text is lossy and intended as a debugging aid, not a promise that the printed code can be compiled or behaves exactly like the original.

採用の歴史

cargo-expand is widely adopted: it is packaged by Homebrew, Nix, Arch Linux, and Alpine in the supplied facts, and crates.io records millions of downloads. Its GitHub repository also has thousands of stars, strong evidence that it is a mainstream Rust diagnostic tool.

Its adoption tracks the rise of procedural macros and derive-heavy frameworks in Rust. When generated code is hard to reason about, `cargo expand` became the common first tool for understanding what the compiler is seeing.

使われ方

Users run `cargo expand` in a Cargo project to print expanded code. Common variants include expanding a test target, selecting a module or item path, disabling rustfmt with `--ugly`, or using configuration under the `[expand]` section of `$CARGO_HOME/config.toml`.

cargo-expand optionally formats output with rustfmt and can use themes or paging configured in Cargo's user config file, making compiler-oriented output easier to read in terminals.

パッケージ好きにとっての重要性

cargo-expand matters because macro expansion is one of Rust packaging's hidden dependency surfaces: derives and procedural macros can add trait impls, bounds, helper items, and code paths that are invisible in source form. Seeing that generated code helps maintainers debug builds, features, and public API behavior.

It is also a classic Cargo-subcommand success story: a thin, focused wrapper around a compiler capability became the community default because it matched how Rust developers actually inspect package code.

タイムライン

• 2016: dtolnay/cargo-expand GitHub repository created.
• 2016: cargo-expand crate first published on crates.io.
• 2026: crates.io metadata shows active releases in the 1.0.x line.

Related projects

• rustc provides the underlying macro expansion output exposed by cargo-expand.
• rustfmt is used to make expanded output more readable when installed.
• syn is referenced in README screenshots and is part of the wider Rust procedural macro tooling ecosystem.

ソース

• https://api.github.com/repos/dtolnay/cargo-expand
• https://crates.io/api/v1/crates/cargo-expand
• https://github.com/dtolnay/cargo-expand#readme
• https://raw.githubusercontent.com/dtolnay/cargo-expand/master/README.md
• input.source_facts.package-manager