cargo-bless 0.1.0

Modernize your Rust dependencies with blessed.rs + live intel
Documentation

cargo-bless

A Cargo subcommand that checks your dependencies against blessed.rs recommendations and suggests modern alternatives.

What it does

  • Scans your Cargo.toml dependency tree (direct + transitive, with features)
  • Matches against a built-in rule database sourced from blessed.rs
  • Detects single-crate replacements and combo optimizations (e.g. dropping serde_json when reqwest has the json feature)
  • Fetches live metadata from crates.io (latest version, downloads) and GitHub (last push, archived status)
  • Optionally applies safe fixes to your Cargo.toml with --fix (preview first with --dry-run)

Installation

From crates.io:

cargo install cargo-bless

From source:

git clone https://github.com/Ruffian-L/cargo-bless
cd cargo-bless
cargo install --path .

Usage

cargo bless                  # scan and report
cargo bless --fix --dry-run  # preview changes without writing
cargo bless --fix            # apply changes (creates .bak backup)
cargo bless --update-rules   # fetch latest rules from blessed.rs

Example

$ cargo bless

🔥 cargo-bless v0.1.0

📋 Scanning dependencies...

📦 Direct dependencies (16)
  • reqwest 0.12.28 [json, default-tls, ...]
  • serde_json 1.0.149 [default, ...]
  ...

Found 16 direct deps, 317 total.

🌐 Fetching live intelligence...

🚀 Modernization report for my-project v0.1.0

 • [LOW] reqwest+serde_json → reqwest with "json" feature
      latest: v0.13.2, 64.6M recent downloads

0 high-impact upgrades available.

$ cargo bless --fix --dry-run

🔍 Dry-run: the following changes would be made:

--- Cargo.toml (original)
+++ Cargo.toml (modified)

- serde_json = "1"

Changes that would be applied:
  ✓ Removed `serde_json`, enabled `json` feature on `reqwest`

Built-in rules

Pattern Suggestion Kind Impact
lazy_static std::sync::LazyLock StdReplacement High
once_cell std::sync::LazyLock / OnceLock StdReplacement High
memmap memmap2 Unmaintained High
failure anyhow + thiserror Unmaintained High
iron axum Unmaintained High
structopt clap v4 (derive) ModernAlternative Medium
actix-web axum ModernAlternative Medium
log tracing ModernAlternative Medium
chrono time ModernAlternative Medium
env_logger tracing-subscriber ModernAlternative Medium
reqwest + serde_json reqwest with json feature FeatureOptimization Low
tokio + async-std tokio only ComboWin Medium
log + env_logger tracing + tracing-subscriber ComboWin Medium
warp axum ModernAlternative Medium
rocket axum ModernAlternative Medium

Rules are embedded at compile time from data/suggestions.json. PRs to add more are welcome.

How --fix works

Only some suggestion types are auto-fixable (the ones that only need Cargo.toml changes):

  • StdReplacement — removes the dep (you still need to update your source code)
  • Unmaintained — renames the dep key to the maintained fork
  • FeatureOptimization — removes the extra dep and enables the feature on the main dep

ModernAlternative and ComboWin are reported but not auto-fixed, since they require source code changes.

Before any edit, --fix creates a Cargo.toml.bak backup and runs cargo update afterward.

How it works

  1. cargo_metadata parses the full resolved dependency tree with features
  2. Rules from data/suggestions.json are matched against direct deps (single-crate and combo patterns)
  3. crates_io_api::SyncClient fetches live metadata (cached to ~/.cache/cargo-bless/ with 1-hour TTL)
  4. octocrab checks GitHub for pushed_at, archived, and star count
  5. toml_edit applies fixes while preserving comments and formatting

Network calls are non-fatal — if you're offline, the rule-based report still works.

License

Licensed under either of

at your option.