Rust project setup

Rust Project Setup

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

Quick Reference

Topic	Reference
Cargo.toml configuration, profiles, dependencies	references/cargo-config.md
Workspace organization, member layout, shared deps	references/workspace-layout.md
GitHub Actions CI, caching, MSRV checks	references/ci-setup.md
Feature flags, conditional compilation, build scripts	references/features-conditional.md
no_std development, embedded targets, cross-compilation	references/no-std.md

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

Use	When
Single crate	Small project, CLI tool, simple library
Workspace	Multiple related crates, shared dependencies, separate compile targets

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

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