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

m11-ecosystem