Current Dependencies (Auto-Injected)

!grep -A 100 '^\[dependencies\]' Cargo.toml 2>/dev/null | head -30 || echo "No Cargo.toml found"

Ecosystem Integration

Layer 2: Design Choices

Core Question

What's the right crate for this job, and how should it integrate?

Before adding dependencies:

• Is there a standard solution?

• What's the maintenance status?

• What's the API stability?

Integration Decision → Implementation

Need

Choice

Crates

Serialization

Derive-based

serde, serde_json

Async runtime

tokio or async-std

tokio (most popular)

HTTP client

Ergonomic

reqwest

HTTP server

Modern

axum, actix-web

Database

SQL or ORM

sqlx, diesel

CLI parsing

Derive-based

clap

Error handling

App vs lib

anyhow, thiserror

Logging

Facade

tracing, log

Thinking Prompt

Before adding a dependency:

-

Is it well-maintained?

• Recent commits?

• Active issue response?

• Breaking changes frequency?

-

What's the scope?

• Do you need the full crate or just a feature?

• Can feature flags reduce bloat?

-

How does it integrate?

• Trait-based or concrete types?

• Sync or async?

• What bounds does it require?

Trace Up ↑

To domain constraints (Layer 3):

"Which HTTP framework should I use?"

    ↑ Ask: What are the performance requirements?

    ↑ Check: domain-web (latency, throughput needs)

    ↑ Check: Team expertise (familiarity with framework)

Question

Trace To

Ask

Framework choice

domain-*

What constraints matter?

Library vs build

domain-*

What's the deployment model?

API design

domain-*

Who are the consumers?

Trace Down ↓

To implementation (Layer 1):

"Integrate external crate"

    ↓ m04-zero-cost: Trait bounds and generics

    ↓ m06-error-handling: Error type compatibility

"FFI integration"

    ↓ unsafe-checker: Safety requirements

    ↓ m12-lifecycle: Resource cleanup

Quick Reference

Language Interop

Integration

Crate/Tool

Use Case

C/C++ → Rust

bindgen

Auto-generate bindings

Rust → C

cbindgen

Export C headers

Python ↔ Rust

pyo3

Python extensions

Node.js ↔ Rust

napi-rs

Node addons

WebAssembly

wasm-bindgen

Browser/WASI

Cargo Features

Feature

Purpose

[features]

Optional functionality

default = [...]

Default features

feature = "serde"

Conditional deps

[workspace]

Multi-crate projects

Error Code Reference

Error

Cause

Fix

E0433

Can't find crate

Add to Cargo.toml

E0603

Private item

Check crate docs

Feature not enabled

Optional feature

Enable in features

Version conflict

Incompatible deps

cargo update or pin

Duplicate types

Different crate versions

Unify in workspace

Crate Selection Criteria

Criterion

Good Sign

Warning Sign

Maintenance

Recent commits

Years inactive

Community

Active issues/PRs

No response

Documentation

Examples, API docs

Minimal docs

Stability

Semantic versioning

Frequent breaking

Dependencies

Minimal, well-known

Heavy, obscure

Anti-Patterns

Anti-Pattern

Why Bad

Better

extern crate

Outdated (2018+)

Just use

#[macro_use]

Global pollution

Explicit import

Wildcard deps *

Unpredictable

Specific versions

Too many deps

Supply chain risk

Evaluate necessity

Vendoring everything

Maintenance burden

Trust crates.io

Related Skills

When

See

Error type design

m06-error-handling

Trait integration

m04-zero-cost

FFI safety

unsafe-checker

Resource management

m12-lifecycle