fix(core): parse components with argument-less $state() instead of silently skipping them

[oekazuma]

Fixes #424.

Problem

let el = $state(); — the idiomatic bind:this declaration — crashed fact extraction: two scans in component-parse.ts (the $state.raw candidates scan and the builtin-state candidates scan) call unwrapTs(init.arguments?.[0]), and unwrapTs dereferenced .type on the undefined argument. The resulting TypeError was swallowed by collectComponentFacts's deliberate never-throw fallback, so the whole file silently contributed emptyComponentFacts — invisible to every rule, with a clean Health 100/100 to show for it.

Verified blast radius: only bare $state() in .svelte components. $state.raw() / $state.frozen() with no argument and argument-less $state() in .svelte.ts runes modules never reached the crashing scans (pinned by a regression test so that stays true).

Fix

unwrapTs now tolerates undefined via an overload pair — one guard in the shared helper covers both current call sites and any future caller, while keeping the non-undefined callers' return type narrow. No call sites changed; the never-throw fallback in component-collect.ts is untouched (it remains the safety net for genuinely malformed files).

Tests

• The issue's exact repro ($state() alongside count/doubled/$effect) yields normal facts — loc, effects, constableStates, plus rawableStates/nonreactiveBuiltinStates to exercise both formerly-crashing scans.
• The typed $state<HTMLDialogElement>() variant from the issue's trigger table.
• .svelte.ts runes module with argument-less $state() (already worked; pinned against regression).
• collectComponentFacts no longer falls back to empty facts for such a file (the user-visible symptom).

Mutation-checked: with the unwrapTs guard reverted, the three .svelte tests fail with the original TypeError; the .svelte.ts pin passes, as expected.

Release note

Changeset (@svelte-vitals/core patch) states the gate movement explicitly: files previously skipped by this crash are now analyzed, so projects using this pattern may see new findings — including critical ones — and a previously green run can fail the default --fail-on critical gate. That is the fix working.

Follow-up (out of scope)

The issue's secondary point — nothing surfaces when a file is skipped by the never-throw fallback — is a real observability gap but a separate design decision (skipped-file counter / stderr note). Filing it separately keeps this a pure crash fix.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Fixed analysis for argument-less $state() declarations so affected components are processed normally instead of being skipped.
  • Restored detection of findings that were previously hidden when these declarations caused parsing errors.
  • Added support for typed argument-less $state<T>() declarations.

• Tests

  • Added regression coverage for component and module-state analysis, including locations, effects, and state findings.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 52031383-9f2f-439c-b98d-4348bdc0e242

📥 Commits

Reviewing files that changed from the base of the PR and between 20d6f16 and a744568.

📒 Files selected for processing (4)

• .changeset/state-noarg-parse-crash.md
• packages/core/src/component-parse.ts
• packages/core/test/component-collect.test.ts
• packages/core/test/component-parse.test.ts

---

📝 Walkthrough

Walkthrough

The parser now handles argument-less $state() declarations without replacing component facts with empty results. Tests cover component, typed, and .svelte.ts module cases. A changeset documents the patch release.

Changes

Argument-less state parsing

Layer / File(s)	Summary
Optional expression unwrapping packages/core/src/component-parse.ts	unwrapTs now accepts an undefined expression and safely returns undefined when $state() has no argument.
Regression coverage and release note packages/core/test/component-parse.test.ts, packages/core/test/component-collect.test.ts, .changeset/state-noarg-parse-crash.md	Tests cover component facts, typed calls, module state declarations, and collection results. The changeset documents the patch release.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• oekazuma/svelte-vitals#112: Introduced the component-facts parser extraction that this change extends.
• oekazuma/svelte-vitals#276: Adds related $state() parsing logic in component-parse.ts.
• oekazuma/svelte-vitals#309: Modifies component-parse.ts for another fact-extraction parsing behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the fix for argument-less $state() component parsing.
Linked Issues check	✅ Passed	The changes restore normal analysis for argument-less, typed, and generic $state() declarations as required by issue #424.
Out of Scope Changes check	✅ Passed	The changeset, implementation, and regression tests directly support the parsing fix and contain no unrelated code changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[oekazuma]

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