refactor(calc): select rulesets by governing-law date

[LKSNDRTMLKV]

Selects the governing ruleset by the date the law attached to the product, not by the wall clock — plus the citation corrections that surfaced while verifying the dates against the Official Journal text of Regulation (EU) 2023/1542.

Primary text was read in full (OJ L 191, 28.7.2023, pp. 1-117). Research and provenance live in dpp-docs/reference/regulatory/BATTERY-2023-1542-CITATION-MAP-2026-07.md.

Citation corrections

Three wrong legal references on numerically correct rules:

• Annex X does not contain the recycled-content targets. Verbatim, Annex X is "LIST OF RAW MATERIALS AND RISK CATEGORIES" — the due-diligence list behind Arts. 48-53. Art. 8(2)/(3) name Annex VIII. The percentages and dates were right; only the citation was wrong. annex_x_shortfalls_* renamed to art8_shortfalls_*.
• Art. 10(6) is the wrong empowerment. It amends the Annex IV parameter list. Minimum values come from Art. 10(5) — two acts, deadlines 18 Feb 2026 and 18 Feb 2027.
• carbonFootprintClass hardcoded an A-E enum that does not exist in law. Art. 7(2) defines no labels and requires the Commission to "review the number of performance classes and the thresholds between them, every three years".

REGULATORY.md had drifted further than the code it documents: both recycled-content phase dates were given as 1 January rather than 18 August, SLI was listed as excluded when Art. 8(2) names it, and LMT was placed in Phase 1 rather than Phase 2.

The date model

Every application date in Art. 7 — and Art. 8(1), Art. 10(2)/(3) — is written as max(fixed date, entry-into-force + N months). A fixed from cannot express that.

• AssessmentClock { law_in_force_on, computed_at } is now the only way to reach a calculator. The wall-clock calculate() overloads are deleted, not deprecated, and there is no AssessmentClock::now() — a convenience wrapper that reads the clock makes the wrong answer the shorter one to write, and the wrong answer here stays invisible until a phase boundary passes.
• Effectivity::{InForce, Pending} replaces EffectiveDateBound. The 2100-01-01 sentinel is gone: it asserted a calendar date for an act that does not exist. Pending governs no date at all and yields a new CalcError::RulesetUndetermined naming the instrument being waited on.
• Assessability<T> replaces Option on resolve_*, separating NotYetInForce / Undetermined / Expired / OutOfScope. None of those is non-compliance, and Option could not tell them apart.
• CalculationReceipt.assessed_as_of records which law-date the calculation was performed against. Without it a receipt names the ruleset it cited but not whether that was the right one to cite.
• CalculatorStatus is now derived from each ruleset's own Effectivity instead of being hand-maintained beside it.

placedOnMarketDate is added to battery schema v2.1.0 and BatteryData, and the battery plugin derives the Art. 8 phase from it. A missing or unparseable date produces its own finding and no determination.

Breaking

Pre-1.0, landing in the unreleased 0.11.0 (latest published is 0.10.0, verified against the crates.io API). dpp-engine pins 0.10.0 and references none of the changed symbols.

• annex_x_shortfalls_{2031,2036} -> art8_shortfalls_{2031,2036}
• Ruleset::effective_dates() -> effectivity(); EffectiveDateBound -> Effectivity
• Ruleset::ensure_active_today() removed
• co2e::calculate / repairability::calculate take an AssessmentClock; calculate_asof removed
• CalculationReceipt::new / for_ruleset take an AssessmentClock
• resolve_repairability returns Assessability<T>
• battery schema v2.1.0 is now currentSchemaVersion; v2.0.0 stays registered so existing passports remain verifiable

Not in this PR

• The conditional max(floor, entry-into-force + N months) arithmetic. No relevant act has entered into force, so it could only be validated against invented fixtures. Specified for whoever picks it up in docs/architecture/EFFECTIVE-DATES.md §4, including the Conditional variant to add and the rule that entry-into-force is read from the OJ, never inferred.
• dpp_domain::CarbonFootprintClass is still an enum { A..E, Other }. The schema was fixed; the type was not. #[serde(other)] means an unrecognised label flattens to Other and the original is lost on round-trip.
• Annex VII state-of-health modelling (SOCE for EV, five parameters for BESS/LMT). Documented in degradation.rs, not built.

Verification

just check and just build-plugins both green: 792 tests, 10 plugin suites.

The gate itself had a hole — plugins/sector-* are excluded from the workspace, so just check never ran their tests. A test-plugins recipe is now wired into check; it immediately caught two real failures this branch had introduced that the old gate reported as green.

Commits are split for review. History here is squash-merged, so they are not individually bisectable.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 91 complexity · 0 duplication

Metric	Results
Complexity	91
Duplication	0

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AI Reviewer: first review requested successfully. AI can make mistakes. Always validate suggestions.

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[codacy-production]

Pull Request Overview

The refactor successfully transitions the ruleset selection from a wall-clock approach to a fixed governing-law date (e.g., placedOnMarketDate). This ensures that compliance audits remain consistent over time, a critical requirement for EU regulatory alignment. Codacy analysis indicates the changes are up to standard with no new quality issues or complexity increases.

Key improvements include the introduction of the AssessmentClock structure, granular Assessability statuses, and corrected citations for Art. 8 recycled content. There are no critical flaws preventing a merge, though there is a minor risk of data loss in the Rust representation of performance classes (hardcoded A-E) compared to the now-dynamic JSON schema.

About this PR

• The dpp_domain::CarbonFootprintClass Rust type remains a hardcoded A-E enum despite the JSON schema being updated to allow arbitrary strings. This may lead to data loss during deserialization if future delegated acts define non-A-E labels.
• The conditional application date arithmetic (calculating the max of a floor date and an entry-into-force offset) is currently deferred. While not immediately blocking as no delegated acts have entered into force, this remains a technical gap that will require implementation once the first acts are published.

Test suggestions

• AssessmentClock enforces that law_in_force_on is provided by the caller and not derived from the wall clock.
• Effectivity::Pending governs no dates and returns a RulesetUndetermined error naming the expected empowerment.
• Assessability enum correctly distinguishes between four distinct reasons for a ruleset being unavailable.
• Recycled content Phase 1 includes SLI batteries and industrial batteries > 2kWh starting precisely on 18 Aug 2031.
• Recycled content Phase 2 includes LMT batteries and previously covered categories starting on 18 Aug 2036.
• Battery plugin reports a missing or malformed placedOnMarketDate as a specific finding rather than assuming a default phase.
• resolve_repairability selects the correct ruleset version based on the law-in-force date.

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[codacy-production]

_{🟡 MEDIUM RISK}

Suggestion: Correcting the citation from Annex X to Art. 8(2)/(3) in the recycled content module is important for legal accuracy. Annex X relates to raw materials, while Art. 8 defines the actual thresholds.

[codacy-production]

_{🟡 MEDIUM RISK}

Suggestion: The prioritization in resolve_repairability (favoring NotYetInForce over Undetermined and Expired) ensures that the most actionable regulatory status is returned, clearly distinguishing between known future obligations and unadopted legislative acts.

[codacy-production]

_{🟡 MEDIUM RISK}

Suggestion: The introduction of AssessmentClock and the deliberate exclusion of a now() constructor is a robust design choice. By requiring the product's regulatory attachment date, the system ensures that audits of older products use the correct historical law.

[codacy-production]

_{🟡 MEDIUM RISK}

Suggestion: A missing or malformed placedOnMarketDate correctly prevents the plugin from asserting shortfalls, defaulting to a NotAssessed status. This design choice is critical for legal accuracy, as it prevents the system from defaulting to the current wall clock and making incorrect retroactive determinations. Ensure that downstream consumers are aware that NotAssessed is the expected state when this date is absent.

[codacy-production]

_{⚪ LOW RISK}

Nitpick: The manual ISO 8601 parsing is functional and safe for no_std usage. It strictly requires the standard format with specific separators, which is appropriate for regulatory compliance where input formats must be rigid.