Existential Birds Beagle Rust Project Setup

Rust Project Setup

Step-by-step guidance for setting up new Rust projects with proper configuration, linting, and CI.

Quick Reference

New Project Checklist

1. Create the Project

# Binary
cargo init my-app

# Library
cargo init --lib my-lib

# Workspace (create Cargo.toml manually)
mkdir my-workspace && cd my-workspace

2. Configure Cargo.toml

Set edition, rust-version (MSRV), and metadata:

[package]
name = "my-app"
version = "0.1.0"
edition = "2024"
rust-version = "1.85"

3. Set Up Linting

Add clippy and rustfmt configuration:

# Cargo.toml
[lints.clippy]
all = { level = "deny", priority = 10 }
pedantic = { level = "warn", priority = 3 }

[lints.rust]
future-incompatible = "warn"
nonstandard_style = "deny"
# unsafe_op_in_unsafe_fn is deny-by-default in edition 2024 — no need to set it

Edition 2024 lint defaults: unsafe_op_in_unsafe_fn is deny by default. Unsafe operations inside unsafe fn require explicit unsafe {} blocks. The gen keyword is reserved — use r#gen if needed as an identifier.

# rustfmt.toml
edition = "2024"
reorder_imports = true
imports_granularity = "Crate"
group_imports = "StdExternalCrate"

4. Configure Profiles

[profile.release]
lto = true
codegen-units = 1
strip = true

5. Set Up CI

Add GitHub Actions workflow for check, clippy, test, and fmt. See references/ci-setup.md.

6. Cargo.lock Policy

• Binaries: Commit Cargo.lock (reproducible builds)
• Libraries: Do NOT commit Cargo.lock (consumers resolve their own versions)
• Add to .gitignore for libraries: Cargo.lock

7. Documentation Setup

For library crates, enable doc lints:

// src/lib.rs
#![deny(missing_docs)]

Prefer #[expect(lint)] over #[allow(lint)] for temporary suppressions — it warns when the suppression becomes unnecessary:

#[expect(dead_code, reason = "used in next PR")]
fn upcoming_feature() {}

Workspace vs Single Crate

Workspaces reduce compile times by sharing dependencies and build artifacts across members.

Project Structure

Binary

my-app/
  Cargo.toml
  rustfmt.toml
  src/
    main.rs
    lib.rs      # separate logic from entry point
  tests/
    integration_test.rs

Library

my-lib/
  Cargo.toml
  rustfmt.toml
  src/
    lib.rs
    module_a.rs
    module_b/
      mod.rs
      types.rs
  tests/
    api_test.rs
  examples/
    basic_usage.rs

Workspace

my-workspace/
  Cargo.toml          # [workspace] definition
  rustfmt.toml        # shared formatting
  crates/
    core/             # shared types and logic
    api/              # HTTP server
    cli/              # command-line interface

Dependency Best Practices

• Pin exact versions for binaries: serde = "=1.0.210"
• Use version ranges for libraries: serde = "1"
• Group features explicitly: tokio = { version = "1", features = ["rt-multi-thread", "macros"] }
• Use [dev-dependencies] for test-only crates
• Review cargo tree for duplicate versions
• Run cargo audit for security vulnerabilities
• Replace once_cell/lazy_static with std::sync::LazyLock (stable since Rust 1.80)

Edition 2024 Migration Notes

When migrating existing projects to edition 2024:

• unsafe fn bodies now require explicit unsafe {} blocks around unsafe operations
• extern "C" {} blocks must be written as unsafe extern "C" {}
• #[no_mangle] and #[export_name] require #[unsafe(no_mangle)] and #[unsafe(export_name)]
• gen is a reserved keyword — rename any gen identifiers to r#gen or choose a different name
• -> impl Trait captures all in-scope lifetimes by default; use + use<'a> for precise control
• ! (never type) falls back to ! instead of () — review match arms and diverging expressions
• Temporaries in if let and tail expressions drop earlier — review code holding locks or guards in these positions

Run cargo fix --edition to auto-fix most mechanical changes.

Setup completion gates

Use these as objective pass conditions after the checklist—not informal “looks done.”

1. Manifest loads — From the project or workspace root, run cargo metadata --format-version 1. Pass: exit code 0 and the output lists your crate(s) (package name matches what you expect).
2. Lint and format — Run cargo clippy --all-targets (add -- -D warnings if warnings must fail) and cargo fmt --check. Pass: both exit 0 before you treat CI as authoritative.
3. CI present — You committed the workflow you intend to run (see references/ci-setup.md). Pass: at least one pipeline run finishes green for check, clippy, tests, and fmt (or the subset you defined).
4. Lockfile policy — Binary crate: Cargo.lock is committed (git ls-files Cargo.lock prints Cargo.lock). Library crate: Cargo.lock is not tracked (empty git ls-files Cargo.lock, or file gitignored and never added). Pass: the index matches that policy with no surprise Cargo.lock changes.

Related Skills

• beagle-rust:rust-best-practices — idiomatic patterns and edition 2024 coding guidance
• beagle-rust:rust-code-review — code review covering ownership, unsafe, and trait design

Source: existential-birds/beagle — distributed by TomeVault.