fix(core): reduce JSON-LD rule false positives (SEO018/019/021) + rendered entity handling

[oekazuma]

Follow-up to #55. These refinements were reviewed and committed locally but never pushed before #55 merged, so they're re-submitted here on their own branch.

Why

The JSON-LD rules from #55 produced false positives on valid, idiomatic structured data, and rendered-mode capture could corrupt JSON before validation.

Changes

Rule / area	Problem	Fix
SEO018	@id (a node identifier, often a relative fragment like #organization) flagged as a relative URL; data:/mailto:/urn:/protocol-relative values also flagged	Drop @id from URL_KEYS; broaden isAbsoluteUrl to accept any URI scheme or // protocol-relative — only scheme-less paths flag
SEO019	schema.org reduced-precision dates (2026, 2026-06) wrongly flagged	isIso8601 accepts year / year-month precision (calendar + range validation kept)
SEO021	"headline": "" / null / [] counted as present (false negative)	New hasNonEmpty helper treats empty/blank/null/empty-array required values as missing
Rendered capture	script.text HTML-entity-decodes (&quot; → "), corrupting JSON before SEO016 parses it	Read via script.rawText — <script> is a raw-text element crawlers don't decode

Docs (en/ja for SEO018, SEO019) updated to match. Tests added for each case (core +10, vite +1).

Validation

pnpm -r test (368: core 165 / vite 58 / cli 136 / mcp 9), pnpm -r typecheck, pnpm lint — all green.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Improved JSON-LD validation to reduce false positives for URLs, dates, and required fields.
  • Accepted more valid URL forms, including protocol-relative links and non-HTTP schemes.
  • Allowed reduced-precision dates such as year-only and year-month formats.
  • Treated empty or blank required values as missing.
  • Preserved JSON-LD script content exactly as written when capturing rendered pages.

• Documentation

  • Clarified JSON-LD rule behavior in the docs.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR updates JSON-LD validation to accept broader URL and ISO date forms, treats blank required values as missing, and preserves raw <script type="application/ld+json"> contents during rendered HTML parsing. Matching docs, tests, and a release note were updated.

Changes

JSON-LD validation updates

Layer / File(s)	Summary
URL and date predicates .changeset/seo-jsonld-false-positives.md, packages/core/src/rules/seo/jsonld-engine.ts, docs/src/content/docs/rules/seo018.md, docs/src/content/docs/ja/rules/seo018.md, docs/src/content/docs/rules/seo019.md, docs/src/content/docs/ja/rules/seo019.md, packages/core/test/jsonld-engine.test.ts, packages/core/test/seo-jsonld-rules.test.ts	isAbsoluteUrl accepts any URI scheme and protocol-relative URLs, URL_KEYS no longer includes @id, isIso8601 accepts reduced-precision dates, and the SEO018/SEO019 docs and tests reflect those checks.
Non-empty required values packages/core/src/rules/seo/jsonld-engine.ts, packages/core/src/rules/seo/seo016-021.ts, packages/core/test/jsonld-engine.test.ts, packages/core/test/seo-jsonld-rules.test.ts	hasNonEmpty(node, key) is added and SEO021 now reports required properties that are missing, blank, or empty rather than only absent keys.
Rendered JSON-LD capture packages/vite/src/providers/rendered/parse-html.ts, packages/vite/test/parse-html.test.ts	Rendered-mode JSON-LD capture switches to rawText, and the test asserts HTML entities are preserved verbatim.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• oekazuma/svelte-vitals#55: Refines the same JSON-LD validation path and rendered JSON-LD capture behavior updated here.

Poem

A bunny hopped through JSON-LD dew,
Sniffed out false alarms and bade them adieu.
Raw script crumbs stayed crisp in the air,
While dates and URLs leapt everywhere. 🐇

🚥 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 summarizes the main change: fewer JSON-LD false positives across SEO018/019/021 and the rendered JSON-LD entity handling fix.
Docstring Coverage	✅ Passed	Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/seo-jsonld-false-positives

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

packages/core/src/rules/seo/jsonld-engine.ts (1)

92-106: 🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Reject out-of-range timezone offsets in isIso8601.

Line 92 accepts any ±dd:dd offset, and Lines 103-106 only range-check the local hh:mm:ss. That means values like 2026-06-26T10:00:00+24:00 or 2026-06-26T10:00:00+00:60 currently return true, so SEO019 will silently accept invalid DateTime values.

Suggested fix

 export function isIso8601(s: string): boolean {
   const str = s.trim();
   if (!/^\d{4}(-\d{2}(-\d{2}(T\d{2}:\d{2}(:\d{2}(\.\d+)?)?(Z|[+-]\d{2}:\d{2})?)?)?)?$/.test(str)) return false;
   const y = Number(str.slice(0, 4));
   const hasMonth = str.length >= 7;
   const hasDay = str.length >= 10;
   const m = hasMonth ? Number(str.slice(5, 7)) : 1;
   if (m < 1 || m > 12) return false;
   if (hasDay) {
     const d = Number(str.slice(8, 10));
     const dt = new Date(Date.UTC(y, m - 1, d));
     if (dt.getUTCFullYear() !== y || dt.getUTCMonth() !== m - 1 || dt.getUTCDate() !== d) return false;
   }
-  const tm = /^\d{4}-\d{2}-\d{2}T(\d{2}):(\d{2})(?::(\d{2}))?/.exec(str);
+  const tm = /^\d{4}-\d{2}-\d{2}T(\d{2}):(\d{2})(?::(\d{2}))?(?:\.\d+)?(?:Z|([+-])(\d{2}):(\d{2}))?$/.exec(str);
   if (tm) {
     const [hh, mm, ss] = [Number(tm[1]), Number(tm[2]), tm[3] !== undefined ? Number(tm[3]) : 0];
     if (hh > 23 || mm > 59 || ss > 59) return false;
+    if (tm[5] !== undefined) {
+      const offH = Number(tm[5]);
+      const offM = Number(tm[6]);
+      if (offH > 23 || offM > 59) return false;
+    }
   }
   return true;
 }

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/core/src/rules/seo/jsonld-engine.ts` around lines 92 - 106,
`isIso8601` currently validates the local time parts but does not reject invalid
timezone offsets, so out-of-range values like +24:00 or +00:60 can still pass.
Update the offset validation in `isIso8601` to parse and range-check the
timezone hours and minutes explicitly, alongside the existing `tm` local-time
checks, and return false when the offset is outside valid ISO 8601 bounds.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@packages/core/src/rules/seo/jsonld-engine.ts`:
- Around line 92-106: `isIso8601` currently validates the local time parts but
does not reject invalid timezone offsets, so out-of-range values like +24:00 or
+00:60 can still pass. Update the offset validation in `isIso8601` to parse and
range-check the timezone hours and minutes explicitly, alongside the existing
`tm` local-time checks, and return false when the offset is outside valid ISO
8601 bounds.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 5aadd58d-e85e-4cbd-acef-2e901523dd9b

📥 Commits

Reviewing files that changed from the base of the PR and between 99cdfbe and 67a5a0e.

📒 Files selected for processing (11)

• .changeset/seo-jsonld-false-positives.md
• docs/src/content/docs/ja/rules/seo018.md
• docs/src/content/docs/ja/rules/seo019.md
• docs/src/content/docs/rules/seo018.md
• docs/src/content/docs/rules/seo019.md
• packages/core/src/rules/seo/jsonld-engine.ts
• packages/core/src/rules/seo/seo016-021.ts
• packages/core/test/jsonld-engine.test.ts
• packages/core/test/seo-jsonld-rules.test.ts
• packages/vite/src/providers/rendered/parse-html.ts
• packages/vite/test/parse-html.test.ts