# dpp-rules
[](https://crates.io/crates/dpp-rules)
[](https://docs.rs/dpp-rules)
[](../../LICENSE)
Pure `#![no_std]`, zero-dependency EU ESPR cross-field regulatory rules.
These are rules that JSON Schema cannot express — "fibre percentages must sum to ~100%", "SVHC concentration > 0.1% triggers disclosure", "surfactant band must be one of the four EU-standard labels". They live here, **once**, and are consumed by both `dpp-domain` (standalone validation, no Wasm host) and the Wasm sector plugins (via `dpp-plugin-sdk::rules`). Every regulatory rule has exactly one implementation.
See `docs/architecture/SECTOR-MODEL-CONSOLIDATION.md` §7 for the design rationale.
---
## No-std constraint
This crate **must remain `#![no_std]` + `alloc` with zero dependencies.** That is the whole reason C1 extracted it from `dpp-domain`: sector plugins compile to `wasm32-wasip1` and cannot pull in the heavier domain crate. If a rule needs `std` or an external crate, the rule is in the wrong place.
The CI `cargo check` target verifies this. Do not break it.
---
## Module structure
```
src/
├── lib.rs re-exports everything at the crate root (backward compat)
│
├── common/
│ ├── country.rs ISO 3166-1 alpha-2 validation ✅
│ ├── numeric.rs percentage helpers, sum checks (placeholder)
│ └── units.rs unit conversion helpers (placeholder)
│
├── chemicals/ REACH / RoHS / EU 2026/405 (cross-sector — never under one sector)
│ ├── svhc.rs REACH Art. 33 concentration validation ✅
│ └── surfactants.rs EU 2026/405 band validation ✅
│
├── textiles/ EU ESPR textile sector
│ ├── fibre.rs fibre_sum_ok, validate_fibre_composition ✅
│ └── care.rs ISO 3758 care symbols (placeholder)
│
├── batteries/ EU Regulation 2023/1542, Annex XIII
│ ├── chemistry.rs allowed chemistries, voltage ranges (placeholder)
│ ├── degradation.rs SOH estimation, cycle life (placeholder)
│ └── recycled_content.rs Co / Li / Ni split thresholds (placeholder)
│
├── electronics/ EU Ecodesign Regulation (ESPR)
│ └── spare_parts.rs availability periods (placeholder)
│ NOTE: repairability scoring → dpp-calc, not here
│
├── metals/ CBAM (EU Regulation 2023/956)
│ ├── aluminium.rs alloy grade, CO₂e per route (placeholder)
│ └── steel.rs BF-BOF / EAF / DRI-EAF, scrap ratio (placeholder)
│
├── construction/ EU CPR 2024/3110 (placeholder)
└── toys/ EN 71 / REACH / EU 2025/2509 (placeholder)
```
Active sectors are batteries, textiles, and electronics. All others have placeholder modules with field documentation; rules will be added as the delegated acts finalise and the sector plugins mature.
---
## Adding a rule
1. Find the right module (sector + sub-concern). If the rule applies to more than one sector, it belongs in `chemicals/` or `common/`, not under any single sector.
2. Write a pure function with primitive borrowing inputs (`&str`, `f64`, `&[T]`). No owned allocations in function arguments.
3. Return `Result<(), String>` for validators, `bool` for predicates.
4. Add a `#[cfg(test)] mod tests` block in the same file.
5. If the symbol needs to be accessible from `dpp-domain` or `dpp-plugin-sdk` callers without the module path, add a `pub use` line in `lib.rs`.
6. Run `cargo test -p dpp-rules` and then `cargo test --workspace` before committing.
---
## Invariants
| `#![no_std]` + `alloc` only | Wasm sector plugins consume this crate; std is unavailable in `wasm32-wasip1` |
| Zero `[dependencies]` in `Cargo.toml` | Keeps the plugin graph lean; any dep here becomes a dep of every plugin |
| Primitive borrowing inputs | Callers adapt their own types; this crate depends on neither `dpp-domain` structs nor `serde_json::Value` |
| One implementation per rule | The only acceptable duplication is a `pub use` re-export in `lib.rs` |
| Repairability scoring → `dpp-calc` | EN 45554 A–E grade calculation belongs to the calculator crate; only field-level validations live here |
| SVHC → `chemicals/` | REACH Art. 33 is cross-sector; it must never be placed under a single sector module |
| `common/` threshold | A helper belongs in `common/` only if it is used by ≥ 2 sector modules and has no sector-specific meaning |