fix(mentor): primary-role mentors are selectable/assignable

getCandidates, getMentorPool and bulkAssign matched MENTOR via roles[] only, so
a user with role=MENTOR but an empty roles[] array (legacy/seeded records, e.g.
Arnaud Blandin on prod) was excluded from the mentor picker and rejected by
bulk assign. Match MENTOR as primary role OR in roles[], mirroring userHasRole.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/server/routers/mentor.ts

@@ -315,7 +315,10 @@ export const mentorRouter = router({
 
       const mentors = await ctx.prisma.user.findMany({
         where: {
-          roles: { has: 'MENTOR' },
+          // MENTOR as primary role OR in the secondary roles[] array. Some legacy
+          // users have role=MENTOR with an empty roles[], so checking roles only
+          // would wrongly exclude them (mirrors userHasRole's fallback).
+          OR: [{ role: 'MENTOR' }, { roles: { has: 'MENTOR' } }],
           status: { not: 'SUSPENDED' },
         },
         select: {
@@ -728,9 +731,11 @@ export const mentorRouter = router({
     .mutation(async ({ ctx, input }) => {
       const mentors = await ctx.prisma.user.findMany({
         where: { id: { in: input.mentorIds } },
-        select: { id: true, name: true, email: true, roles: true },
+        select: { id: true, name: true, email: true, role: true, roles: true },
       })
-      const validMentors = mentors.filter((m) => m.roles.includes('MENTOR'))
+      // Accept MENTOR as primary role OR in roles[] (legacy users may have
+      // role=MENTOR with an empty roles[] array).
+      const validMentors = mentors.filter((m) => m.roles.includes('MENTOR') || m.role === 'MENTOR')
       if (validMentors.length === 0) {
         throw new TRPCError({
           code: 'BAD_REQUEST',
@@ -1574,7 +1579,9 @@ export const mentorRouter = router({
     .query(async ({ ctx, input }) => {
       const mentors = await ctx.prisma.user.findMany({
         where: {
-          roles: { has: 'MENTOR' },
+          // MENTOR as primary role OR in the secondary roles[] array (see
+          // getCandidates: legacy users may have role=MENTOR with empty roles[]).
+          OR: [{ role: 'MENTOR' }, { roles: { has: 'MENTOR' } }],
           status: { not: 'SUSPENDED' },
         },
         select: {

tests/unit/mentor-primary-role-assignable.test.ts

@@ -0,0 +1,98 @@
+import { describe, it, expect, beforeAll, afterAll, vi } from 'vitest'
+
+vi.mock('@/lib/email', async () => {
+  const actual = await vi.importActual<typeof import('@/lib/email')>('@/lib/email')
+  return {
+    ...actual,
+    sendMentorBulkAssignmentEmail: vi.fn(async () => true),
+    sendTeamMentorIntroductionEmail: vi.fn(async () => true),
+  }
+})
+
+import { prisma, createCaller } from '../setup'
+import {
+  createTestProgram,
+  createTestCompetition,
+  createTestRound,
+  createTestProject,
+  createTestProjectRoundState,
+  createTestUser,
+  cleanupTestData,
+  uid,
+} from '../helpers'
+import { mentorRouter } from '../../src/server/routers/mentor'
+
+/**
+ * Regression: a user whose MENTOR role is the PRIMARY role but whose roles[]
+ * array is empty (legacy/seeded records, e.g. prod user "Arnaud Blandin") must
+ * still be selectable + assignable on the mentor config page. Previously the
+ * candidate query filtered `roles: { has: 'MENTOR' }`, which excludes an empty
+ * roles[] even when role === 'MENTOR'.
+ */
+describe('mentor.getCandidates / bulkAssign — primary-role-only mentors are assignable', () => {
+  let programId = ''
+  let projectId = ''
+  let mentorId = ''
+  let adminId = ''
+  const userIds: string[] = []
+
+  beforeAll(async () => {
+    const program = await createTestProgram()
+    programId = program.id
+    const competition = await createTestCompetition(program.id)
+    const round = await createTestRound(competition.id, {
+      roundType: 'MENTORING',
+      status: 'ROUND_DRAFT', // draft → assignment emails are deferred
+    })
+    const project = await createTestProject(program.id)
+    projectId = project.id
+    await createTestProjectRoundState(project.id, round.id)
+
+    // The crux: primary role MENTOR, but roles[] is EMPTY.
+    const mentor = await prisma.user.create({
+      data: {
+        id: uid('u'),
+        email: `${uid('arnaud')}@test.local`,
+        name: 'Primary Only Mentor',
+        role: 'MENTOR',
+        roles: [],
+        status: 'ACTIVE',
+      },
+    })
+    mentorId = mentor.id
+
+    const admin = await createTestUser('SUPER_ADMIN')
+    adminId = admin.id
+    userIds.push(mentor.id, admin.id)
+  })
+
+  afterAll(async () => {
+    await cleanupTestData(programId, userIds)
+  })
+
+  it('getCandidates includes a primary-role-only mentor', async () => {
+    const caller = createCaller(mentorRouter, {
+      id: adminId,
+      email: 'admin@test.local',
+      role: 'SUPER_ADMIN',
+    })
+    const res = await caller.getCandidates({ projectId })
+    const ids = res.candidates.map((c: { id: string }) => c.id)
+    expect(ids).toContain(mentorId)
+  })
+
+  it('bulkAssign accepts a primary-role-only mentor and creates the assignment', async () => {
+    const caller = createCaller(mentorRouter, {
+      id: adminId,
+      email: 'admin@test.local',
+      role: 'SUPER_ADMIN',
+    })
+    // Must not throw "None of the selected users have the MENTOR role".
+    await caller.bulkAssign({ mentorIds: [mentorId], projectIds: [projectId] })
+
+    const assignment = await prisma.mentorAssignment.findFirst({
+      where: { projectId, mentorId },
+    })
+    expect(assignment).not.toBeNull()
+  })
+})