Implement build.rs loader, generate build_generated.rs

[ERnsTL]

Task 2 — Implement Minimal build.rs Loader

Objective

Read and parse flowd.build.toml inside build.rs.

Requirements

1. Add build.rs to project root.

2. Use toml crate to parse file.

3. Validate:

   • At least one component exists.
   • No duplicate name.
   • crate and struct fields are not empty.

4. If validation fails → panic!().

Acceptance Criteria

• cargo build fails if config invalid.
• cargo build succeeds if valid.

No code generation yet.

---

Task 3 — Generate build_generated.rs

Objective

Generate Rust code during build.

Requirements

In build.rs:

1. Create file:

   $OUT_DIR/build_generated.rs
   

2. Generate:

3.1 Use Statements

use repeat_component::RepeatComponent;
use drop_component::DropComponent;

Based on config.

3.2 Metadata Registration Function

pub fn build_component_library() -> Arc<RwLock<ComponentLibrary>> {
    Arc::new(RwLock::new(ComponentLibrary::new(vec![
        RepeatComponent::get_metadata(),
        DropComponent::get_metadata(),
    ])))
}

Acceptance Criteria

• Generated file compiles.
• Removing a component from config removes it from metadata.

[ERnsTL]

Task 2:

Implemented minimal build.rs loader for flowd.build.toml with required validation: non-empty component list, unique name, non-empty crate and struct, and panic on invalid config. cargo build succeeds for valid config and fails for invalid config.

Task 3:

Implemented code generation to $OUT_DIR/build_generated.rs, including generated use statements and generated build_component_library() metadata registration from config. Generated file compiles, and component removal from config propagates to generated metadata/factory output.