svelte-rs-2

Use whenever adding an e2e compiler-output test (our JS vs the reference compiler) — a new cluster case under `tasks/compiler_tests/`.

🧩 PARITY · Turn one divergence from the Original into a test per affected case (does not fix).

Use when starting any compiler task or session before touching parser/analyze/transform/ast/codegen/css/diagnostics code, before proposing a design or writing code, and when the task grows into a new layer and you need its PRD invariants.

🔪 SDT · verdict-directed review of backend codegen/transform. Use when auditing codegen/transform for smart-analyzer / dumb-codegen violations, or when porting a transform/codegen visitor from the Original.

The required unit-test format for `crates/**/src/**` — use when writing or reviewing a Rust `#[test]`, a test helper, or an `assert_*`. Not for `tasks/compiler_tests/` (use add-test) or `tasks/diagnostic_tests/` (use add-diagnostic-test).

PRD editorial standard for docs/. Use when writing a new PRD, extending one, or reviewing changes under docs/ — and when another skill needs the PRD rules.

Create a new diagnostic parity test case. Use when the user asks to add a diagnostic test, create a new `tasks/diagnostic_tests/cases/<name>` case, or capture a false positive/false negative against npm `svelte/compiler` before implementation.

Parse JS code through OXC and display ESTree JSON AST. Use proactively when implementing codegen, transforms, or debugging to understand how OXC represents a specific JS/TS construct in its AST. MUST use this skill before writing any new AST node construction in builder.rs, before implementing a new codegen visitor, or when unsure how OXC represents a JS pattern (destructuring, spread, optional chaining, etc.). Also use when debugging AST mismatch issues or when porting a new Svelte feature that involves JS expression handling.

Compiler profiling and hotspot analysis.

Rust style rules for any .rs change.

Bump the pinned Svelte version across the whole repo — pin, vendored `original/`, docs, README, playground import map — then regenerate expected outputs and run the checks. Manual launch only via `/update-svelte`.

Use when you have an ad-hoc Svelte component or `.svelte.js`/`.svelte.ts` module (pasted inline, scratch file, or a single existing file) and need a one-shot parity check against `svelte/compiler` without registering a persistent case.

MUST consult before writing any code related to Svelte 4 legacy features. Contains mandatory naming conventions, doc-comment format, and isolation rules for legacy code. Use this skill whenever touching on:directive, bind:this legacy syntax, Svelte 4 deprecated features, code marked LEGACY(svelte4), or when porting/implementing any feature that has both a Svelte 5 and a Svelte 4 variant. Failure to follow these conventions creates tech debt that blocks future cleanup.