quick-check

name: quick-check description: 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. argument-hint: " [--mode=auto|runes|legacy] [--generate=client|server] [--dev] [--filename=] [--print=diff|ours|ref|both]" allowed-tools: Bash, Write

Quick-check component or module

One-shot compile of a single Svelte component or standalone .svelte.js / .svelte.ts module against the reference compiler. Components compare both the emitted JS and the scoped CSS (CSS is whitespace-normalized via compact_css_for_injection, so indentation diffs do not trip parity). Modules compare JS only (no CSS, no template). Prints OK on parity or a per-section diff on mismatch. Does NOT register persistent tests or modify compiler code.

When NOT to use

• Persisted parity finding (sweep mismatch, registered case) → /dig.
• Directory-level survey across many files → just sweep-run <dir> --dry-run.
• Capturing the behavior as a permanent test → /add-test (compiler) or /add-diagnostic-test (diagnostics).
• About to modify compiler crates to fix the divergence → escalate to /dig first.

The Rust side dispatches by file extension: .svelte.js / .svelte.ts → compile_module, anything else → compile. The reference side does the same.

Step 1: Resolve the input

• Argument is an existing .svelte / .svelte.js / .svelte.ts path → use as-is.
• Argument is inline source → write to a scratch file first. Pick the extension by content:
  • looks like a component (has markup, <script>, <style>, or directives) → tasks/quick_check/scratch.svelte.
  • looks like a standalone module (top-level import/export, $state/$derived at module scope, no markup) → tasks/quick_check/scratch.svelte.js.
  • TypeScript module → tasks/quick_check/scratch.svelte.ts.

All three scratch files are git-ignored. Never write to tasks/compiler_tests/cases2/.

Step 2: Run

just quick-check <path> [flags]

Flags (all optional, both sides — our compiler and reference — receive them):

• --mode=auto|runes|legacy — compile mode. Default: our compiler's default (runes unless <svelte:options runes={false}/> flips it). Ignored for module inputs (modules are always runes).
• --generate=client|server — runtime target. Default: client.
• --dev — dev-build flag.
• --filename=<name> — override filename (affects component-name resolution for components; passed to compile_module for modules).
• --print=diff|ours|ref|both — output mode. Default diff (interleaved < ours / ref > comparison, silent body on match). Use both to print the full rust and reference outputs side-by-side (labeled ==== RUST JS ==== / ==== REFERENCE JS ====), printed even when they match — this is the way to read a fork in context when the interleaved diff is ambiguous (note: < left is OURS, > right is REFERENCE). ours / ref print just one side's full output. Exit code is unchanged (0 match / 1 mismatch).

If the user explicitly named a mode, generate target, or dev flag, pass it through — do not assume defaults match.

Under the hood this invokes cargo run -q -p quick_check -- <path> [flags] after installing the reference compiler's npm deps. Flags are forwarded to the reference side via QUICK_CHECK_CONFIG.

Step 3: Interpret the exit code

• 0 — our JS and (whitespace-normalized) CSS both match reference. Report OK + JS line count + CSS byte count.
• 1 — JS and/or CSS mismatch. Diff printed per section under -- JS -- / -- CSS (whitespace-normalized) -- headers. Summarize the categories of divergence (e.g. missing CSS scope class on a bare-pseudo combinator, statement ordering, missing helper call, wrong rune lowering). Call out the first mismatching block in each section.
• 2 — bad input (missing file, bad arguments).
• 3 — our Rust compiler panicked or produced no JS. Name the panic message and guess the first owning layer: parser, analyze, transform, codegen.
• 4 — reference compiler (node side) failed. Likely invalid Svelte syntax or missing npm deps.

Step 4: Report

Keep report terse. Include:

• exit code summary (OK / MISMATCH / PANIC / INPUT / NODE)
• applied flags (mode/generate/dev/filename) — they appear in the binary's output line; surface them so the user sees what was actually probed
• first owning layer if panic or mismatch is clearly layer-scoped
• suggested next command if the user wants durable coverage:
  • /diagnose — turn mismatch into a spec-owned follow-up
  • /add-test <name> — capture passing behavior as a persistent case

Rules

• No edits to compiler crates.
• No edits to tasks/compiler_tests/cases2/ or tasks/compiler_tests/test_v3.rs.
• Reusable scratch files only: tasks/quick_check/scratch.svelte, tasks/quick_check/scratch.svelte.js, tasks/quick_check/scratch.svelte.ts.
• Do NOT commit scratch files — all three are git-ignored.
• If inline source appears to be SvelteKit / MDsveX specific (uses imports/types that won't resolve in isolation), warn and skip. Pure standalone runes-in-module code is fine even with unresolved external imports — compile_module doesn't need them to resolve.