fix(core): CORRECT001 stop flagging itemless {#each} and fix backwards rationale

[oekazuma]

Summary

Fixes #135 — two problems in CORRECT001 (keyed each), found while auditing existing rules against the official Svelte docs.

• False positive on itemless each blocks: the official {#each ...} docs document the itemless form ({#each { length: 8 }, i}) as a first-class "render N times" pattern (the chess-board example). CORRECT001 flagged it as unkeyed, but there is no item identity to key on — the only possible key is the index itself, which is a no-op. collectEachBlocks now skips each blocks with no item context (node.context == null), verified against the real parser.
• Rationale described the unkeyed mechanism backwards: it claimed unkeyed each "destroys and recreates DOM nodes" on reorder. The docs describe the opposite — a key lets Svelte "insert, move, and delete" nodes, rather than adding/removing at the end and rewriting the data of nodes in between. The user-facing consequence (state/focus loss) was right; the mechanism was backwards. Reworded in the rule and the rule docs (en/ja).

Test plan

• New tests in component-parse.test.ts: itemless each is ignored, and stays ignored even if given a (meaningless) index key.
• pnpm build && pnpm typecheck && pnpm test && pnpm lint: all pass (core 349, cli 345, vite 84, mcp 13).
• pnpm --filter docs check: 0 errors.
• Patch changeset for @svelte-vitals/core + svelte-vitals (behavioral change to a shipped rule).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of itemless {#each} blocks so they are no longer treated as keyed items in error checks.
  • Reduced false positives for rendering patterns that repeat content without meaningful item identity.

• Documentation

  • Clarified guidance for the keyed each rule, including which {#each} patterns are ignored and why keys matter for DOM updates and state retention.

• Tests

  • Added coverage for itemless {#each} cases to confirm they are ignored correctly.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: f9ddc34a-c72a-439b-adc9-76221c05c473

📥 Commits

Reviewing files that changed from the base of the PR and between 8598b42 and 18b11af.

📒 Files selected for processing (6)

• .changeset/correct001-itemless-each.md
• docs/src/content/docs/ja/rules/correct001.md
• docs/src/content/docs/rules/correct001.md
• packages/core/src/component-parse.ts
• packages/core/src/rules/correctness/correct001-002.ts
• packages/core/test/component-parse.test.ts

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📝 Walkthrough

Walkthrough

CORRECT001's each-block collection now skips itemless {#each} blocks (node.context == null) so they are no longer falsely flagged for missing keys. The rule's rationale text and English/Japanese documentation were updated to accurately describe the unkeyed reorder mechanism, with new tests and a patch changeset added.

Changes

CORRECT001 itemless each fix

Layer / File(s)	Summary
Skip itemless each blocks in collectEachBlocks packages/core/src/component-parse.ts, packages/core/test/component-parse.test.ts	collectEachBlocks now guards on node.context != null before recording hasKey, and new tests assert itemless {length: n} each blocks (with or without an index key) produce empty eachBlocks.
Correct rationale text and docs packages/core/src/rules/correctness/correct001-002.ts, docs/src/content/docs/rules/correct001.md, docs/src/content/docs/ja/rules/correct001.md	The correct001EachKey rationale and both English/Japanese docs are reworded to describe Svelte appending/removing nodes at the end and rewriting middle node data when keys are missing, and both docs now list the itemless "render N times" pattern as an ignored case.
Changeset for patch release .changeset/correct001-itemless-each.md	Adds a patch changeset for @svelte-vitals/core and svelte-vitals describing the itemless each fix and corrected rationale.

Estimated code review effort: 2 (Simple) | ~12 minutes

Possibly related PRs

• oekazuma/svelte-vitals#68: Prior PR introduced the collectEachBlocks/correct001EachKey pipeline that this PR directly refines to exclude itemless each blocks.

🚥 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 is concise and accurately summarizes the main behavioral and rationale fix.
Linked Issues check	✅ Passed	The PR addresses both linked requirements: it ignores itemless {#each} blocks and rewrites the incorrect rationale in code and docs.
Out of Scope Changes check	✅ Passed	The changes stay within the linked issue scope, with only the expected docs, tests, and changeset updates.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

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• Create stacked PR
• Commit on current branch

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