cargo-feat-0.1.3 is not a library.

cargo-feat

Disclaimer: I am not a Rust professional and I am not claiming to be one - I built this simply because it was useful to me. 90%+ of the code was written solely by me and not just vibe-coded like most of the "personal tools" being released these days; very small edits were done using ChatGPT. Claude was only used to generate the .gitignore, this README, and code comments.

A fast command-line tool for Rust developers to instantly look up the available features of any crate on crates.io - directly in your terminal, with no browser required.

Why

When adding a dependency, finding out what features it exposes usually means opening a browser, searching crates.io or docs.rs, and scrolling through documentation. cargo-feat removes that friction: one command gives you a color-coded list of every feature the crate exposes, which ones are enabled by default, and what each feature pulls in.

Demo

$ feat reqwest

- reqwest's features are in the following list -
    * default
         blocking
         json

    - blocking                (default)
    - json                    (default)
    - http2
    - native-tls
    - rustls-tls
    - gzip
    - brotli
    - ...

Installation

From source

Requires a recent stable Rust toolchain.

git clone https://github.com/vunholy/cargo-feat.git
cd cargo-feat
cargo build --release

The compiled binary will be at target/release/feat (or feat.exe on Windows).

To make it available globally, copy it to a directory in your PATH:

# Linux / macOS
cp target/release/feat ~/.local/bin/feat

# Windows (PowerShell - adjust path as needed)
Copy-Item target\release\feat.exe "$env:USERPROFILE\.cargo\bin\feat.exe"

Usage

feat <crate-name> [version] [all|nd]

Argument	Required	Description
`<crate-name>`	Yes	Name of the crate to look up. Underscores are automatically normalized to hyphens.
`[all\|nd]`	No	Feature filter. `all` (default) shows every feature. `nd` hides the default feature block but still lists all features and marks the ones that are part of the default set.
`[version]`	No	Specific crate version to query. Defaults to the latest stable release.

The version and all|nd arguments are order-independent — feat tokio 1.35.0 nd and feat tokio nd 1.35.0 both work.

Examples

# List all features for the latest version of reqwest
feat reqwest

# List features without the default block - features that are part of the default set are still shown and marked
feat reqwest nd

# List features for a specific version
feat tokio 1.35.0

# Combine a version with a filter
feat tokio 1.35.0 nd

# Crate names with underscores work fine
feat proc_macro2

Output Format

- crate's features are in the following list -
    * default          <- the default feature set (lists which features it enables)
         feature-a
         feature-b

    - feature-a  (default)   <- enabled by default
    - feature-b  (default)
    - feature-c              <- opt-in feature
    - feature-d

The * default block lists which features are enabled when you add the crate without specifying features.
Features marked (default) are part of the default feature set.
Using nd hides the * default block but keeps all features in the list, still marking the ones that belong to the default set.
Internal features (names starting with __) are always hidden.

Exit Codes

Code	Meaning
`0`	Success
`100`	Failed to create the HTTP client
`101`	Network request failed (no response received)
`102`	Failed to read the response body
`103`	Failed to parse the API response (unexpected JSON shape)
`104`	The specified version was not found for the crate

Performance

cargo-feat is built with performance as a first-class concern:

MiMalloc - Microsoft's high-performance memory allocator replaces the system allocator globally.
simd-json - SIMD-accelerated JSON parsing (AVX2/FMA when available).
hashbrown + ahash - faster HashMap and HashSet than the standard library.
Aggressive release profile - fat LTO, single codegen unit, opt-level = "z", stripped symbols.
reqwest with full compression support (gzip, brotli, zstd, deflate) and Hickory DNS.

The binary is small and starts fast, making it suitable for use inside scripts and CI.

Dependencies

Crate	Purpose
`reqwest`	Async-capable HTTP client (used in blocking mode)
`simd-json`	SIMD-accelerated JSON deserialization
`serde`	Derive macros for JSON deserialization
`mimalloc`	Global high-performance memory allocator
`hashbrown`	Fast `HashMap` / `HashSet` backed by Swiss tables
`ahash`	Non-cryptographic, high-speed hash function
`colorize`	ANSI escape code helpers for colored terminal output
`fake_user_agent`	Generates realistic browser user-agent strings

Build Configuration

The .cargo/config.toml enables additional compiler flags for the Windows MSVC target:

target-cpu=native - compile for the host CPU to unlock all supported ISA extensions.
target-feature=+avx2,+fma - explicitly enable AVX2 and FMA for simd-json.
rust-lld.exe - LLVM linker for faster link times.
/OPT:REF, /OPT:ICF - dead-code elimination and identical-COMDAT-folding at link time.

If you are building for a different target or a CPU without AVX2, remove or adjust those flags in .cargo/config.toml.

License

Licensed under the Apache License, Version 2.0.

cargo-feat 0.1.3