feat: try to detect mailing lists as event attendees

src/components/Editor/Invitees/InviteesListSearch.vue

@@ -46,6 +46,10 @@
 					<div v-if="option.type === 'circle' || option.type === 'contactsgroup'">
 						{{ option.subtitle }}
 					</div>
+					<div v-else-if="option.looksLikeMailingList" class="invitees-search-list-item__warning">
+						<AlertCircleOutline :size="14" />
+						{{ $t('calendar', 'This might be a mailing list. Invitations will not work.') }}
+					</div>
 				</div>
 			</div>
 		</template>
@@ -62,12 +66,13 @@
 } from '@nextcloud/vue'
 import debounce from 'debounce'
 import GoogleCirclesCommunitiesIcon from 'vue-material-design-icons/GoogleCirclesCommunities.vue'
+import AlertCircleOutline from 'vue-material-design-icons/AlertCircleOutline.vue'
 import {
 	circleGetMembers,
 	circleSearchByName,
 } from '../../../services/circleService.js'
 import isCirclesEnabled from '../../../services/isCirclesEnabled.js'
-import { removeMailtoPrefix } from '../../../utils/attendee.js'
+import { looksLikeMailingList, removeMailtoPrefix } from '../../../utils/attendee.js'
 import { randomId } from '../../../utils/randomId.js'
 
 export default {
@@ -76,6 +81,7 @@
 		Avatar,
 		NcSelect,
 		GoogleCirclesCommunitiesIcon,
+		AlertCircleOutline,
 	},
 
 	props: {
@@ -145,6 +151,7 @@
 							timezoneId: null,
 							hasMultipleEMails: false,
 							dropdownName: query,
+							looksLikeMailingList: looksLikeMailingList(query),
 						})
 					}
 				}
@@ -281,6 +288,7 @@
 						timezoneId: result.tzid,
 						hasMultipleEMails,
 						dropdownName: name + ' ' + email,
+						looksLikeMailingList: looksLikeMailingList(email),
 					})
 				})
 
@@ -318,4 +326,11 @@
 :deep(.avatardiv) {
 	overflow: visible !important;
 }
+
+.invitees-search-list-item__warning {
+	display: flex;
+	align-items: center;
+	gap: 4px;
+	color: var(--color-warning);
+}
 </style>

src/utils/attendee.js

@@ -57,6 +57,61 @@
 	return removeMailtoPrefix(organizer.uri)
 }
 
+/**
+ * Heuristically check if an email address looks like a mailing list address
+ *
+ * @param {string} email Email address to check (with or without mailto: prefix)
+ * @return {boolean} True if the address looks like a mailing list
+ */
+export function looksLikeMailingList(email) {
+	if (typeof email !== 'string') {
+		return false
+	}
+
+	const address = removeMailtoPrefix(email).toLowerCase()
+	const atIndex = address.indexOf('@')
+	if (atIndex === -1) {
+		return false
+	}
+
+	const local = address.slice(0, atIndex)
+	const domain = address.slice(atIndex + 1)
+
+	const exactMatches = new Set([
+		'list', 'lists', 'ml', 'announce', 'announcements', 'noreply', 'no-reply',
+		'newsletter', 'newsletters', 'mailer-daemon', 'postmaster', 'sympa',
+		'majordomo', 'listserv', 'mailman', 'dmarc', 'bounce', 'bounces',
+		'subscribe', 'unsubscribe',
+	])
+	if (exactMatches.has(local)) {
+		return true
+	}
+
+	const suffixes = [
+		'-bounces', '-request', '-subscribe', '-unsubscribe', '-owner', '-help',
+		'-announce', '-devel', '-discuss', '-commits', '-bugs', '-patches',
+		'-users', '-list', '+bounces', '+subscribe',
+	]
+	if (suffixes.some((s) => local.endsWith(s))) {
+		return true
+	}
+
+	const knownDomains = new Set([
+		'googlegroups.com', 'groups.io', 'freelists.org',
+		'yahoogroups.com', 'listserv.com', 'topica.com',
+	])
+	if (knownDomains.has(domain)) {
+		return true
+	}
+
+	const knownSubdomainPrefixes = ['lists.', 'ml.', 'listserv.', 'mailman.', 'sympa.']
+	if (knownSubdomainPrefixes.some((p) => domain.startsWith(p))) {
+		return true
+	}
+
+	return false
+}
+
 /**
  * Check if the current user is an attendee
  *

tests/javascript/unit/utils/attendee.test.js

@@ -5,6 +5,7 @@
 
 import {
 	addMailtoPrefix,
+	looksLikeMailingList,
 	organizerDisplayName,
 	removeMailtoPrefix,
 } from '../../../../src/utils/attendee'
@@ -33,6 +34,51 @@ describe('utils/attendee test suite', () => {
 		expect(addMailtoPrefix(undefined)).toEqual("mailto:")
 	})
 
+	describe('looksLikeMailingList', () => {
+		it('detects exact local-part matches', () => {
+			expect(looksLikeMailingList('announce@example.com')).toBe(true)
+			expect(looksLikeMailingList('mailman@example.org')).toBe(true)
+			expect(looksLikeMailingList('noreply@example.com')).toBe(true)
+			expect(looksLikeMailingList('lists@example.com')).toBe(true)
+		})
+
+		it('detects local-part suffix matches', () => {
+			expect(looksLikeMailingList('dev-bounces@example.org')).toBe(true)
+			expect(looksLikeMailingList('project-request@example.com')).toBe(true)
+			expect(looksLikeMailingList('calendar-users@example.com')).toBe(true)
+			expect(looksLikeMailingList('app+bounces@example.com')).toBe(true)
+		})
+
+		it('detects known mailing list domains', () => {
+			expect(looksLikeMailingList('group@googlegroups.com')).toBe(true)
+			expect(looksLikeMailingList('list@groups.io')).toBe(true)
+			expect(looksLikeMailingList('user@freelists.org')).toBe(true)
+		})
+
+		it('detects known mailing list subdomains', () => {
+			expect(looksLikeMailingList('user@lists.nextcloud.com')).toBe(true)
+			expect(looksLikeMailingList('someone@mailman.apache.org')).toBe(true)
+			expect(looksLikeMailingList('foo@sympa.example.com')).toBe(true)
+		})
+
+		it('handles mailto: prefix', () => {
+			expect(looksLikeMailingList('mailto:announce@example.com')).toBe(true)
+			expect(looksLikeMailingList('mailto:john@example.com')).toBe(false)
+		})
+
+		it('returns false for regular email addresses', () => {
+			expect(looksLikeMailingList('john@example.com')).toBe(false)
+			expect(looksLikeMailingList('dev@example.com')).toBe(false)
+			expect(looksLikeMailingList('alice@company.com')).toBe(false)
+		})
+
+		it('returns false for invalid input', () => {
+			expect(looksLikeMailingList('notanemail')).toBe(false)
+			expect(looksLikeMailingList(null)).toBe(false)
+			expect(looksLikeMailingList(undefined)).toBe(false)
+		})
+	})
+
 	it('should extract a display name of an organizer', () => {
 		const commonName = 'My Name'
 		const uri = 'uri@test.com'