rust-wasm

name: rust-wasm description: Rust development patterns for the FD workspace (crate structure, testing, WASM)

Rust + WASM Development Skill

Workspace Layout

fast-draft/
├── Cargo.toml          # Workspace root
├── crates/
│   ├── fd-core/       # Data model, parser, emitter, layout
│   ├── fd-render/     # Vello/wgpu renderer, hit testing
│   └── fd-editor/     # Sync engine, tools, undo/redo, input
├── fd-vscode/         # VS Code extension (TypeScript + WASM)
└── examples/
    └── demo.fd

Common Commands

Build & Test

cargo check --workspace        # Fast type check
cargo test --workspace         # Run all tests
cargo test -p fd-core         # Test one crate
cargo test -- --nocapture      # See println!/dbg! output
cargo clippy --workspace       # Lint
cargo fmt --all                # Format

WASM Build

# Install wasm-pack if needed
cargo install wasm-pack

# Build for web target
wasm-pack build crates/fd-render --target web

# Build with specific features
wasm-pack build crates/fd-render --target web -- --features wasm

Coding Patterns

Adding a New Node Type

1. Add variant to NodeKind enum in crates/fd-core/src/model.rs
2. Add parsing logic in parse_node() in crates/fd-core/src/parser.rs
3. Add emission logic in emit_node() in crates/fd-core/src/emitter.rs
4. Add intrinsic size in intrinsic_size() in crates/fd-core/src/layout.rs
5. Add rendering in paint_node() in crates/fd-render/src/paint.rs
6. Add hit testing in hit_test_node() in crates/fd-render/src/hit.rs
7. Write tests for round-trip: parse → emit → re-parse

Adding a New Style Property

1. Add field to Style struct in model.rs
2. Parse it in parse_style_property() and parse_node_property() in parser.rs
3. Emit it in emit_style_block() and emit_node() in emitter.rs
4. Merge it in merge_style() in model.rs
5. Apply it to rendering in paint.rs

Adding a New Tool

1. Implement the Tool trait in crates/fd-editor/src/tools.rs
2. Handle input events → produce GraphMutation values
3. Register in tool selection (future: toolbar UI)

Adding a New Constraint

1. Add variant to Constraint enum in model.rs
2. Parse in parse_constraint_line() / parse_node_property()
3. Emit in emit_constraint() in emitter.rs
4. Resolve in apply_constraint() in layout.rs

Key Dependencies

Testing Conventions

• Every new parser feature must have a round-trip test
• Test files go in examples/ as .fd files
• Use pretty_assertions for diff-friendly assertions
• Test names: parse_<feature>, emit_<feature>, roundtrip_<feature>, layout_<feature>