rust-devenv-setup

name	rust-devenv-setup
description	Reproducible Nix-based Rust development environment setup with devenv, rust-overlay, clippy, rustfmt, and rust-analyzer.
user-invocable	false

Rust Development Environment Setup

Set up a complete, reproducible Rust development environment using devenv and rust-overlay.

Tools Included

Tool	Purpose
devenv	Nix-based declarative development environment
rust-overlay	Nix overlay for flexible Rust toolchain selection
clippy	Rust linter
rustfmt	Rust formatter
rust-analyzer	Rust LSP for IDE support
cbindgen	C header generation from Rust FFI crates (optional)

Prerequisites

• Nix package manager installed
• direnv installed and hooked into shell
• devenv CLI installed

Implementation Workflow

Before running the setup script, gather parameters from the user using AskUserQuestion.

Step 1: Infer defaults

• PROJECT_NAME: Infer from the current directory name or Cargo.toml package name
• RUST_CHANNEL: Default to stable
• RUST_EDITION: Default to 2024
• EXTRA_PACKAGES: Infer from Cargo.toml dependencies (e.g. if volcap-ffi uses cdylib → add cbindgen)

Step 2: Ask the user to confirm

Use AskUserQuestion to confirm or adjust parameters. Ask all questions in a single call.

Example:

AskUserQuestion({
  questions: [
    {
      question: "What is the project name?",
      header: "Project",
      options: [
        { label: "<inferred-name>", description: "Inferred from current directory" },
        { label: "custom", description: "Enter a different name" }
      ],
      multiSelect: false
    },
    {
      question: "Which Rust channel?",
      header: "Rust Channel",
      options: [
        { label: "stable (Recommended)", description: "Latest stable release" },
        { label: "nightly", description: "Nightly with unstable features" },
        { label: "beta", description: "Next stable candidate" }
      ],
      multiSelect: false
    },
    {
      question: "Extra packages needed?",
      header: "Extras",
      options: [
        { label: "None", description: "Base Rust toolchain only" },
        { label: "cbindgen", description: "C/C++ header generation for FFI crates" },
        { label: "cargo-nextest", description: "Faster test runner" },
        { label: "cargo-watch", description: "File watcher for auto-rebuild" }
      ],
      multiSelect: true
    }
  ]
})

Step 3: Run setup.sh

Build the command from the user's answers and execute.

Step 4: Add rust-overlay input

After running the script, add the rust-overlay input:

cd "${TARGET_DIR}" && devenv inputs add rust-overlay github:oxalica/rust-overlay --follows nixpkgs

This step is required because devenv inputs add modifies devenv.yaml with a lock entry that cannot be templated.

Setup Script

setup.sh generates configuration files and directory structure.

Environment Variables

Variable	Description	Default
PROJECT_NAME	Project name in kebab-case	Required
RUST_CHANNEL	Rust toolchain channel (stable, nightly, beta)	stable
EXTRA_PACKAGES	Space-separated extra nix packages (e.g. rust-cbindgen cargo-nextest)	(empty)
TARGET_DIR	Output directory	Current directory

Usage

# Basic setup
PROJECT_NAME="my-project" \
  bash "${CLAUDE_PLUGIN_ROOT}/skills/rust-devenv-setup/setup.sh"

# With extras
PROJECT_NAME="my-ffi-lib" RUST_CHANNEL="stable" \
  EXTRA_PACKAGES="rust-cbindgen" \
  bash "${CLAUDE_PLUGIN_ROOT}/skills/rust-devenv-setup/setup.sh"

Generated Files

File	Purpose
devenv.yaml	Nix flake inputs (nixpkgs + rust-overlay) + cachix
devenv.nix	Rust toolchain + extra packages
.envrc	direnv integration for auto-activation

Note: devenv.yaml is generated without the rust-overlay input lock. Run devenv inputs add rust-overlay ... after generation (Step 4).

Post-Setup

After running the script:

# Add rust-overlay input (required for languages.rust.channel)
devenv inputs add rust-overlay github:oxalica/rust-overlay --follows nixpkgs

# Activate the environment
direnv allow

# Verify
rustc --version
cargo --version

Key Gotchas

use_devenv: command not found in direnv

The .envrc must contain eval "$(devenv direnvrc)" before use devenv. This is NOT a global direnv setting — it must be per-project.

languages.rust.channel requires rust-overlay

Without the rust-overlay input, devenv will error:

error: To use 'languages.rust.channel', run:
  $ devenv inputs add rust-overlay github:oxalica/rust-overlay --follows nixpkgs

nixpkgs package naming

Some Rust tools have different names in nixpkgs:

Tool	nixpkgs package name
cbindgen	pkgs.rust-cbindgen (NOT pkgs.cbindgen)
cargo-nextest	pkgs.cargo-nextest
cargo-watch	pkgs.cargo-watch

Use nix search nixpkgs <keyword> to verify package names.

Verification

# Check devenv status
devenv info

# Run clippy
cargo clippy

# Check formatting
cargo fmt --check

# Build
cargo check

Customization References

• FFI / cdylib crates — see references/ffi-variants.md