parser: compose leading action with as-enters persisted choice (Anointed Peacekeeper ETB)

[keloide]

Summary

Implements the previously-Unimplemented ETB line of Anointed Peacekeeper — "As ~ enters the battlefield, look at an opponent's hand, then choose any card name." — by composing existing engine primitives into four general, reusable building blocks. No new engine enum variant.

Implementation method (required)

• Produced via the /engine-implementer pipeline (plan → review-plan → implement → review-impl → commit)
• Not /engine-implementer — explain why below

The plan-review caught two Delta phase-rs#4 defects (offset-into-original vs. ~-substituted text; an over-broad peeled-slot guard) which were folded in before implementation; the implementation-review returned "essentially clean, no HIGH/MED," and its three LOW items were resolved.

CR references

All reused verbatim from existing in-repo annotations (docs/MagicCompRules.txt is network-blocked in this environment and could not be freshly grepped):

• CR 614.1c / 614.1d — "as ~ enters" self-replacement scope & composition (oracle_replacement.rs).
• CR 701.20a / 701.20e — reveal (public) vs. look-at (private) hand; RevealHand { reveal: false } (reveal_hand.rs).
• CR 800.4a — "an opponent" controller choice; first-opponent resolution is two-player-exact, multiplayer-simplified (honestly annotated).
• CR 201.3 / 607.2d / 613.1 — card-name choice / persisted chosen attribute (test annotations).

Verification

Developer track — Tilt is down in this environment, so cargo was run directly.

• cargo fmt --all — clean.
• cargo test -p engine --lib — 14,686 pass, 0 real failures, including regressions as_enters_choose_a_color, as_enters_choose_two_colors, as_enters_choose_a_creature_type, as_enters_choose_a_number_sentence_ending_period, as_enters_choose_does_not_match_shock_land, enters_tapped_then_choose_color_composes_tap_and_choice (Thriving land). (The 2 apparent failures were a truncated local card-data.json artifact — snuff_out_from_card_database_* / witherbloom_card_object_* self-skip on a clean tree, confirmed.)
• cargo test -p engine --test anointed_peacekeeper_etb — 1 pass (drives the real cast → ETB replacement → private hand-look → name-a-card pipeline; asserts persisted ChosenAttribute::CardName, RevealHand { reveal:false } over the opponent's hand not the controller's, and both cost-tax statics bound).
• cargo clippy -p engine --lib --test anointed_peacekeeper_etb -- -D warnings — clean, exit 0.
• Gate A — ./scripts/check-parser-combinators.sh exit 0 (no output on success; no violations).

cargo test -p engine (all 145 integration binaries) was intentionally not run — it link-fills the container disk. Only --lib and the single new --test were built. CI has full disk headroom.

What changed (build for the class, not the card)

#	Delta	File	Class unlocked
1	Accept "any card name" in try_parse_named_choice	parser/oracle_effect/mod.rs	every "choose any card name" card (alongside the a/nonland/creature/land forms)
2	Accept non-targeted "an opponent's hand" in parse_hand_possessive_target	parser/oracle_effect/imperative.rs	every non-targeted "look at / reveal an opponent's hand" card
3	RevealHand player-from-filter fallback via collect_player_targets	game/effects/reveal_hand.rs	every non-targeted RevealHand reached with no player target slot
4	Compose an optional leading action before the persisted choice in parse_as_enters_choose	parser/oracle_replacement.rs	the general "As ~ enters, ⟨action⟩, then choose ⟨X⟩" template

Lines 3 & 4 of the card (the spell / activated-ability cost taxes keyed to the chosen name) already parsed and already consume a persisted ChosenAttribute::CardName; this change makes the ETB establish that persisted name plus the private hand-look.

Anchored on (≥2 analogous implementations per delta, same combinator family)

• Delta parser: compose leading action with as-enters persisted choice (Anointed Peacekeeper ETB) #1 ← sibling CardName arms tag("a card name") / tag("a nonland card name") (oracle_effect/mod.rs:17754-17757); determiner-variant arms tag("a color other than ") / tag("a color") (mod.rs:17731,17737).
• Delta Add Render Silent #2 ← value(Typed(Opponent), tag("target opponent's hand")) (imperative.rs:3137-3140); value(Player, tag("target player's hand")) (imperative.rs:3136).
• Delta chore: update coverage stats and badges phase-rs/phase#3 ← collect_player_targets(state, ability, &target) in effects/phase_out.rs:51,91 and effects/effect.rs:411.
• Delta chore: update coverage stats and badges phase-rs/phase#4 ← scan_preceded(...) in oracle_effect/search.rs:93,105,201 & oracle_modal.rs:561; the existing SetTapState{SelfRef}.sub_ability(choose) composition in the same function (oracle_replacement.rs:1756-1762).

Scope expansion

None. Pure composition of existing effects (RevealHand + Choose) plus one additive resolver fallback. No new Effect/enum variant; no frontend/AI/multiplayer-filter/targeting registration touched (lines 3/4 already consume the chosen name this ETB now establishes).

Known limitation (honest, out of scope)

This card does not flip to coverage-supported after this change, because of a separate, pre-existing gap unrelated to line 2: line 4 ("Activated abilities of sources with the chosen name cost {2} more to activate unless they're mana abilities") parses to StaticMode::ReduceAbilityCost, which has no exemption field, so the CR 605.1a "unless they're mana abilities" clause is dropped and the swallow-check detect_condition_unless correctly emits a Condition_Unless swallowed-clause warning. This is proven independent of this change: a probe card containing only lines 1/3/4 (no ETB) emits the identical warning. Modeling that exemption spans the cost-modification subsystem (adding exemption: ActivationExemption across ~17 ReduceAbilityCost sites + resolver application + a resolver test) and belongs in a dedicated follow-up PR. This diff does not mask the dropped line-4 semantic; it only implements line 2.

🤖 Generated with Claude Code

https://claude.ai/code/session_019mjar7ovGZua3ANz9r76fk

---

Generated by Claude Code