feat(parser): N-way Oxford-comma compound-subject keyword static — Shalai, Voice of Plenty (CR 611.3a)

[jsdevninja]

Summary

Fixes #5383.

parse_compound_subject_keyword_static (crates/engine/src/parser/oracle_static/evasion.rs) decomposes the compound player+object keyword-grant pattern "You and <object subject> have <keyword>" (Sigarda, Heron's Grace; Serra's Emissary; Gruul Spellbreaker) into an object-half Continuous/AddKeyword def and a player-half Hexproof/Shroud/PlayerProtection def, since a single StaticDefinition can't carry both a player scope and an object scope.

Its subject match was hard-coded to the literal seam "you and " — exactly one object conjunct. Shalai, Voice of Plenty's real Oracle text uses a 3-item Oxford-comma list instead:

Flying
You, planeswalkers you control, and other creatures you control have hexproof.
{4}{G}{G}: Put a +1/+1 counter on each creature you control.

(verified via Scryfall, oracle_id: a0c47ab6-dfb4-46ee-a3f7-9e1521b4bb4b)

Because the line starts with "You, " rather than "You and ", the tag match failed immediately and the line fell through to the generic fallback, which couldn't resolve it either — client/public/card-data.json recorded it as Unimplemented("static_structure", "Static pattern matched but line failed static parser: …"). Shalai's entire signature ability was silently dropped.

Why this is a class, not a card

The object-only N-way Oxford-comma case already works (parse_type_phrase + distribute_controller_to_or, proven by the Silkguard test and Kismet), but only when a single trailing suffix distributes backward across bare type-noun legs with no clause of their own. Shalai's shape is different: "you" is the first list item, and each subsequent conjunct ("planeswalkers you control", "other creatures you control") is a complete, independently-resolvable subject phrase — exactly what parse_rule_static_subject_filter already resolves one at a time inside the existing 2-item function. Nothing peeled the leading "you" token off an arbitrary-length Oxford list and Or-combined the resolved remainder.

This is a straight generalization of the function's "object subject" axis from exactly-one-conjunct to N-conjuncts, following this repo's "parameterize, don't proliferate" convention rather than hand-rolling a Shalai-specific branch.

Changes

• evasion.rs: parse_compound_subject_keyword_static now accepts "you, " (Oxford-comma N-item form) as an alternate lead to the existing "you and " (bare 2-item form). The comma gate keeps the two grammars disjoint — the 2-item path's existing fallthrough to parse_rule_static_subject_filter (which itself resolves an object subject with an internal bare "and", e.g. "artifacts and creatures you control", via parse_type_phrase's own trailing-suffix distribution) is completely unchanged.
• New parse_oxford_object_conjuncts helper: nom-based (split_once_on), peels ", "-separated conjuncts plus the final ", and "/"and " connector, resolves each conjunct through the existing parse_rule_static_subject_filter, and Or-combines them. Applies the same "no second player scope" guard the 2-item form already applies, now per conjunct.
• Both existing call sites of parse_compound_subject_keyword_static (the direct dispatch and the inverted "As long as <cond>, …" rewrite path) pick up the generalization automatically since it's one function, not a new sibling dispatcher.
• shared.rs: updated the dispatch-site comment to document the new N-item form.
• tests.rs: flips no existing test (none previously exercised this exact shape); adds:
  • compound_subject_keyword_static_splits_shalai_three_way — the real card, asserting the 2-way object Or (planeswalkers you control; other creatures you control) and the player-half Hexproof mode.
  • compound_subject_keyword_static_declines_oxford_list_unresolvable_conjunct — boundary guard: an unresolvable conjunct must strict-fail the whole line, not silently drop the bad disjunct.
  • compound_subject_keyword_static_splits_four_item_oxford_list — arity generality check (synthetic 4-item list → 3-way object Or), proving the splitter isn't hard-coded to Shalai's 3-item arity.

CR references

• CR 611.3a — a continuous effect generated by a static ability applies to whatever its text indicates.
• CR 702.11a/CR 702.11b — hexproof.
• CR 702.16 — protection.
• CR 702.18 — shroud.

Verification

• cargo fmt -p engine -- --check — clean, no diff.
• Local cargo check/cargo test could not be run to completion in the environment this PR was authored in — the sandbox has no working MSVC linker (link.exe on PATH resolves to Git for Windows' coreutils link, not the MSVC linker) and no Docker/WSL fallback, so native build-script compilation fails for unrelated foundational crates (serde, proc-macro2, etc.) before reaching this crate's code. I verified the change through careful manual review (type/signature cross-checks against every function called, hand-traced the split logic against the real Shalai text and three synthetic inputs) and via cargo fmt's parse-clean check, but please treat CI as the first real compile/test signal for this PR and let me know if anything surfaces.

Scope Expansion

None.

[gemini-code-assist]

Code Review

This pull request adds support for parsing the Oxford-comma N-item form of compound-subject keyword-grant statics (such as on Shalai, Voice of Plenty) by introducing the parse_oxford_object_conjuncts helper. This allows resolving multiple independent object subjects into an Or filter alongside the player-half keyword grant. Symmetrical unit tests have been added to verify both successful multi-item parsing and strict-fail behavior on unresolvable conjuncts. No review comments were provided, and the changes are architecturally sound and compliant with the repository style guide.

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[github-actions]

Parse changes introduced by this PR · 1 card(s), 3 signature(s) (baseline: main b96ee5f0a7dd)

1 card(s) · static/Continuous · added: Continuous (affects=you control planeswalker or another you control creature, mods=grant Hexproof)

Examples: Shalai, Voice of Plenty

1 card(s) · static/Hexproof · added: Hexproof (affects=you)

Examples: Shalai, Voice of Plenty

1 card(s) · ability/static_structure · removed: static_structure

Examples: Shalai, Voice of Plenty

1 card(s) had Oracle-text changes (errata/reprint) — excluded as non-parser.

[matthewevans]

Maintainer review: current head cleanly handles the Oxford-comma compound-subject static class; parse-diff limited to Shalai.