cargo-workflows

Cargo Workflows

Purpose

Guide agents through Cargo workspaces, feature management, build scripts (build.rs), CI integration, incremental compilation, and the Cargo tool ecosystem.

Triggers

• "How do I set up a Cargo workspace with multiple crates?"
• "How do features work in Cargo?"
• "How do I write a build.rs script?"
• "How do I speed up Cargo builds in CI?"
• "How do I audit my Rust dependencies?"
• "What is cargo nextest and should I use it?"

Workflow

1. Workspace setup

my-project/
├── Cargo.toml           # Workspace root
├── Cargo.lock           # Single lock file for all members
├── crates/
│   ├── core/
│   │   └── Cargo.toml
│   ├── cli/
│   │   └── Cargo.toml
│   └── server/
│       └── Cargo.toml
└── tools/
    └── codegen/
        └── Cargo.toml

# Workspace root Cargo.toml
[workspace]
members = [
    "crates/core",
    "crates/cli",
    "crates/server",
    "tools/codegen",
]
resolver = "2"   # Feature resolver v2 (required for edition 2021)

# Shared dependency versions (workspace.dependencies)
[workspace.dependencies]
serde = { version = "1", features = ["derive"] }
tokio = { version = "1", features = ["full"] }
anyhow = "1"

# Shared profile settings
[profile.release]
lto = "thin"
codegen-units = 1

# Member Cargo.toml
[package]
name = "myapp-core"
version.workspace = true
edition.workspace = true

[dependencies]
serde.workspace = true    # Inherit from workspace
anyhow.workspace = true

2. Feature flags

[features]
default = ["std"]

# Simple flag
std = []

# Feature that enables another feature
full = ["std", "async", "serde-support"]

# Feature with optional dependency
async = ["dep:tokio"]
serde-support = ["dep:serde", "serde/derive"]

[dependencies]
tokio = { version = "1", optional = true }
serde = { version = "1", optional = true }

# Build with specific features
cargo build --features "async,serde-support"

# Build with no default features
cargo build --no-default-features

# Build with all features
cargo build --all-features

# Check feature combinations
cargo check --no-default-features
cargo check --all-features