fix: the robots element follows the Go grammar and keeps a value it cannot parse (WR-24)

parseRobots accepted 2027-02-30 (Date.parse rolls it over) and refused
max-snippet:+5, both unlike classes/robots_value.go. A value it could not
parse showed every group as Inherit and the first click serialised the
empty model, dropping the stored directives. Dates are now checked as
calendar dates, a sign is accepted, and an unparsed value is kept with a
note, the controls off and an explicit Reset.

assets/src/elements/labels.ts

@@ -44,6 +44,8 @@ export interface Labels {
   noimageindex: string
   unavailableAfter: string
   invalidNumber: string
+  robotsUnparsed: string
+  robotsReset: string
   // E3
   desktop: string
   mobile: string
@@ -166,6 +168,8 @@ const en: Labels = {
   noimageindex: 'Do not index images (noimageindex)',
   unavailableAfter: 'Remove from results after',
   invalidNumber: 'Enter a whole number, -1 or more.',
+  robotsUnparsed: 'The stored value “:value” is not one this editor can show. It stays as it is until you reset it.',
+  robotsReset: 'Reset',
   desktop: 'Desktop',
   mobile: 'Mobile',
   device: 'Preview device',
@@ -283,6 +287,8 @@ const pl: Labels = {
   noimageindex: 'Nie indeksuj obrazów (noimageindex)',
   unavailableAfter: 'Usuń z wyników po dniu',
   invalidNumber: 'Wpisz liczbę całkowitą, -1 lub większą.',
+  robotsUnparsed: 'Zapisanej wartości „:value” ten edytor nie potrafi pokazać. Zostaje bez zmian, dopóki jej nie wyzerujesz.',
+  robotsReset: 'Wyzeruj',
   desktop: 'Komputer',
   mobile: 'Telefon',
   device: 'Urządzenie podglądu',

assets/src/elements/robots.ts

@@ -1,4 +1,4 @@
-import { el, emit, icon, jsonAttr, labelsFor, plural, uid, uiLocaleOf, type Labels } from './labels'
+import { el, emit, fmt, icon, jsonAttr, labelsFor, plural, uid, uiLocaleOf, type Labels } from './labels'
 
 export const ROBOTS_TAG = 'golem15-seo-robots'
 
@@ -35,6 +35,26 @@ export function emptyRobots(): Robots {
   }
 }
 
+/**
+ * Whether s is a real calendar date YYYY-MM-DD, as Go's time.Parse checks
+ * it (2027-02-30 is not; Date.parse would roll it over into March).
+ */
+export function validDate(s: string): boolean {
+  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(s)
+  if (!m) {
+    return false
+  }
+  const year = Number(m[1])
+  const month = Number(m[2])
+  const day = Number(m[3])
+  if (month < 1 || month > 12 || day < 1) {
+    return false
+  }
+  const leap = (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0
+  const days = [31, leap ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month - 1]
+  return day <= days
+}
+
 /** Parses a robots value; null when it is malformed. */
 export function parseRobots(value: string): Robots | null {
   const r = emptyRobots()
@@ -75,7 +95,8 @@ export function parseRobots(value: string): Robots | null {
         break
       case 'max-snippet':
       case 'max-video-preview': {
-        if (arg === null || !/^-?\d+$/.test(arg)) return null
+        // An optional sign, like Go's strconv.Atoi.
+        if (arg === null || !/^[+-]?\d+$/.test(arg)) return null
         const n = Number.parseInt(arg, 10)
         if (n < -1) return null
         if (name === 'max-snippet') r.maxSnippet = n
@@ -87,7 +108,7 @@ export function parseRobots(value: string): Robots | null {
         r.maxImagePreview = arg
         break
       case 'unavailable_after':
-        if (arg === null || !/^\d{4}-\d{2}-\d{2}$/.test(arg) || Number.isNaN(Date.parse(arg + 'T00:00:00Z'))) return null
+        if (arg === null || !validDate(arg)) return null
         r.unavailableAfter = arg
         break
       default:
@@ -128,6 +149,9 @@ export class SeoRobotsElement extends HTMLElement {
   private current = ''
   private model: Robots = emptyRobots()
   private open = false
+  // The stored value does not parse: it is kept as it is, the controls are
+  // off and only Reset replaces it (a click must never drop it silently).
+  private unparsed = false
 
   get value(): string {
     return this.current
@@ -139,7 +163,9 @@ export class SeoRobotsElement extends HTMLElement {
       return
     }
     this.current = next
-    this.model = parseRobots(next) ?? emptyRobots()
+    const parsed = parseRobots(next)
+    this.unparsed = parsed === null
+    this.model = parsed ?? emptyRobots()
     this.open = this.open || advancedCount(this.model) > 0
     this.render()
   }
@@ -160,6 +186,9 @@ export class SeoRobotsElement extends HTMLElement {
   }
 
   private commit(): void {
+    if (this.unparsed) {
+      return
+    }
     this.current = serializeRobots(this.model)
     emit(this, 'summer-change', { value: this.current })
     this.render()
@@ -167,7 +196,7 @@ export class SeoRobotsElement extends HTMLElement {
 
   private render(): void {
     const labels = this.labels()
-    const disabled = this.hasAttribute('disabled')
+    const disabled = this.hasAttribute('disabled') || this.unparsed
     const options = jsonAttr<Record<string, unknown>>(this, 'options', {})
     const inheritLabel = options.scope === 'type' ? labels.siteDefault : labels.inherit
     this.classList.toggle('seo-robots--invalid', this.hasAttribute('invalid'))
@@ -231,7 +260,25 @@ export class SeoRobotsElement extends HTMLElement {
     }
     panel.append(checks)
 
-    this.replaceChildren(groups, row, panel)
+    const parts: HTMLElement[] = [groups, row, panel]
+    if (this.unparsed) {
+      const note = el('div', 'seo-robots__unparsed')
+      note.setAttribute('role', 'status')
+      note.append(icon('triangle-alert'), el('span', '', fmt(labels.robotsUnparsed, { value: this.current })))
+      if (!this.hasAttribute('disabled')) {
+        const reset = el('button', 'seo-robots__reset', labels.robotsReset)
+        reset.type = 'button'
+        reset.dataset.focusKey = 'reset'
+        reset.addEventListener('click', () => {
+          this.unparsed = false
+          this.model = emptyRobots()
+          this.commit()
+        })
+        note.append(reset)
+      }
+      parts.unshift(note)
+    }
+    this.replaceChildren(...parts)
     if (focused) {
       this.querySelector<HTMLElement>(`[data-focus-key="${focused}"]`)?.focus()
     }
@@ -348,7 +395,7 @@ export class SeoRobotsElement extends HTMLElement {
     input.dataset.focusKey = 'unavailableAfter'
     input.value = this.model.unavailableAfter
     input.addEventListener('change', () => {
-      this.model.unavailableAfter = /^\d{4}-\d{2}-\d{2}$/.test(input.value) ? input.value : ''
+      this.model.unavailableAfter = validDate(input.value) ? input.value : ''
       this.commit()
     })
     wrap.append(input)

assets/src/elements/styles.css

@@ -242,6 +242,27 @@ golem15-seo-robots .seo-robots__check input {
   accent-color: var(--c-primary);
 }
 
+golem15-seo-robots .seo-robots__unparsed {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 8px;
+  margin-bottom: 12px;
+  color: var(--c-danger);
+  font-size: 13px;
+}
+
+golem15-seo-robots .seo-robots__reset {
+  min-height: 32px;
+  padding: 0 12px;
+  border: 1px solid var(--c-border);
+  border-radius: 8px;
+  background: transparent;
+  color: inherit;
+  font: inherit;
+  cursor: pointer;
+}
+
 golem15-seo-robots.seo-robots--invalid .seo-robots__track {
   border-color: var(--c-danger);
 }

classes/robots_value_test.go

@@ -108,6 +108,17 @@ func TestRobotsValueMalformed(t *testing.T) {
 	}
 }
 
+// TestRobotsValueSigned: a signed number is accepted and stored without
+// its plus sign, as the element's grammar reads it (WR-24).
+func TestRobotsValueSigned(t *testing.T) {
+	if got, err := NormalizeRobots("max-snippet:+5"); err != nil || got != "max-snippet:5" {
+		t.Fatalf("NormalizeRobots(max-snippet:+5) = %q, %v", got, err)
+	}
+	if _, err := NormalizeRobots("unavailable_after:2028-02-29"); err != nil {
+		t.Fatalf("leap day: %v", err)
+	}
+}
+
 func TestRobotsValueInherit(t *testing.T) {
 	parse := func(v string) Robots {
 		t.Helper()

tests/elements/robots.test.ts

@@ -73,11 +73,37 @@ describe('E2 value grammar', () => {
   })
 
   it('malformed values are refused like the Go grammar', () => {
-    for (const bad of [',', 'index,', 'index,noindex', 'follow,nofollow', 'noarchive,noarchive', 'index:1', 'noarchive:yes', 'max-snippet', 'max-snippet:abc', 'max-snippet:-2', 'max-snippet:1.5', 'max-image-preview:huge', 'unavailable_after:2027-13-01', 'unavailable_after:27-01-01', 'none', 'noodp']) {
+    for (const bad of [',', 'index,', 'index,noindex', 'follow,nofollow', 'noarchive,noarchive', 'index:1', 'noarchive:yes', 'max-snippet', 'max-snippet:abc', 'max-snippet:-2', 'max-snippet:1.5', 'max-image-preview:huge', 'unavailable_after:2027-13-01', 'unavailable_after:27-01-01', 'unavailable_after:2027-02-30', 'unavailable_after:2027-02-29', 'unavailable_after:2027-04-31', 'unavailable_after:2027-01-00', 'max-snippet:+-1', 'none', 'noodp']) {
       expect(parseRobots(bad), bad).toBeNull()
     }
   })
 
+  it('accepts what the Go grammar accepts (WR-24): a leap day and a signed number', () => {
+    expect(serializeRobots(parseRobots('unavailable_after:2028-02-29') as Robots)).toBe('unavailable_after:2028-02-29')
+    expect(serializeRobots(parseRobots('max-snippet:+5') as Robots)).toBe('max-snippet:5')
+    expect(serializeRobots(parseRobots('max-video-preview:-1') as Robots)).toBe('max-video-preview:-1')
+  })
+
+  it('a stored value it cannot parse is kept, shown and replaced only by Reset (WR-24)', () => {
+    const node = document.createElement('golem15-seo-robots') as HTMLElement & { value: string }
+    node.setAttribute('ui-locale', 'en')
+    document.body.append(node)
+    node.value = 'noindex,unavailable_after:2027-02-30'
+    const seen: string[] = []
+    node.addEventListener('summer-change', (ev) => seen.push((ev as CustomEvent).detail.value))
+    expect(node.querySelector('.seo-robots__unparsed')?.textContent).toContain('noindex,unavailable_after:2027-02-30')
+    const segment = node.querySelector('[data-focus-key="follow-2"]') as HTMLButtonElement
+    expect(segment.disabled).toBe(true)
+    segment.click()
+    expect(seen).toEqual([])
+    expect(node.value).toBe('noindex,unavailable_after:2027-02-30')
+    ;(node.querySelector('.seo-robots__reset') as HTMLButtonElement).click()
+    expect(seen).toEqual([''])
+    expect(node.querySelector('.seo-robots__unparsed')).toBeNull()
+    ;(node.querySelector('[data-focus-key="index-2"]') as HTMLButtonElement).click()
+    expect(seen).toEqual(['', 'noindex'])
+  })
+
   it('the element emits the fixed-order value and "" when both groups inherit', () => {
     const node = document.createElement('golem15-seo-robots') as HTMLElement & { value: string }
     document.body.append(node)