fix(import): построчные ошибки до записи

- preflight занятого логина и неактивной целевой группы
- applied=false с номером строки, без частичных студентов
- LDD-IMPORT-003; baseline 58 claims / 368 тестов

services/identity-service/src/main/kotlin/ru/ysu/lms/identity/roster/GroupImportService.kt

@@ -41,6 +41,23 @@ class GroupImportService(
         restoreInactiveStatuses: Boolean = false,
     ): ImportResult {
         val parsed = parser.parse(filename, bytes)
+        validationFailure(parsed)?.let { return it }
+        val cohort = parsed.cohort ?: return ImportResult(applied = false)
+        val group =
+            try {
+                findOrCreateGroup(cohort)
+            } catch (ex: ConflictException) {
+                return ImportResult(
+                    applied = false,
+                    groupName = cohort.name,
+                    errors = listOf(ImportError(parsed.students.firstOrNull()?.row ?: 0, ex.message.orEmpty())),
+                )
+            }
+        return applyStudents(parsed, cohort, group, actorAccountId, restoreInactiveStatuses)
+    }
+
+    /** Ошибки, которые должны быть показаны до любой записи в БД. */
+    private fun validationFailure(parsed: ParsedGroup): ImportResult? {
         if (parsed.errors.isNotEmpty()) {
             return ImportResult(
                 applied = false,
@@ -55,11 +72,20 @@ class GroupImportService(
                 errors = listOf(ImportError(0, "Не удалось определить группу: проверьте поля потока, курса, номера и степени")),
             )
         }
-        val group = findOrCreateGroup(cohort)
+        val preflight = preflightErrors(parsed)
+        return if (preflight.isEmpty()) null else ImportResult(applied = false, groupName = cohort.name, errors = preflight)
+    }
+
+    private fun applyStudents(
+        parsed: ParsedGroup,
+        cohort: GroupCohort,
+        group: GroupEntity,
+        actorAccountId: UUID?,
+        restoreInactiveStatuses: Boolean,
+    ): ImportResult {
         val added = mutableListOf<Credential>()
         val updated = mutableListOf<String>()
         val skipped = mutableListOf<ImportError>()
-
         parsed.students.forEach { parsedStudent ->
             val student = upsertStudent(parsedStudent, cohort, added, updated, restoreInactiveStatuses)
             if (student.status == StudentStatus.ACTIVE) {
@@ -85,6 +111,26 @@ class GroupImportService(
         )
     }
 
+    /**
+     * Проверки, которые нельзя откладывать до записи: иначе конфликт уникальности
+     * откатит весь импорт без номера строки. Здесь же ловим дубли внутри файла.
+     */
+    private fun preflightErrors(parsed: ParsedGroup): List<ImportError> {
+        val errors = mutableListOf<ImportError>()
+        val seen = HashSet<String>()
+        parsed.students.forEach { student ->
+            if (!seen.add(student.studentNo)) {
+                errors += ImportError(student.row, "Студент ${student.studentNo} повторяется в файле")
+                return@forEach
+            }
+            val exists = students.findByStudentNo(student.studentNo) != null
+            if (!exists && accounts.existsByLogin(student.studentNo)) {
+                errors += ImportError(student.row, "Логин ${student.studentNo} уже занят другим аккаунтом")
+            }
+        }
+        return errors
+    }
+
     private fun findOrCreateGroup(cohort: GroupCohort): GroupEntity {
         val existing =
             groups.findByStreamAndDegreeAndNumberAndCourseAndEnrollmentYear(

services/identity-service/src/test/kotlin/ru/ysu/lms/identity/roster/GroupServiceIntegrationTest.kt

@@ -2,6 +2,7 @@ package ru.ysu.lms.identity.roster
 
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertNull
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
 import org.springframework.beans.factory.annotation.Autowired
@@ -16,12 +17,15 @@ import ru.ysu.lms.common.ConflictException
 import ru.ysu.lms.common.UnauthorizedException
 import ru.ysu.lms.identity.auth.AuthService
 import ru.ysu.lms.identity.auth.LoginRequest
+import ru.ysu.lms.identity.domain.Account
 import ru.ysu.lms.identity.domain.MembershipAction
 import ru.ysu.lms.identity.domain.StudentStatus
+import ru.ysu.lms.identity.repo.AccountRepository
 import ru.ysu.lms.identity.repo.EnrollmentRepository
 import ru.ysu.lms.identity.repo.GroupRepository
 import ru.ysu.lms.identity.repo.MembershipHistoryRepository
 import ru.ysu.lms.identity.repo.StudentRepository
+import ru.ysu.lms.security.LmsRole
 import java.util.UUID
 
 @SpringBootTest
@@ -58,6 +62,8 @@ class GroupServiceIntegrationTest {
 
     @Autowired lateinit var students: StudentRepository
 
+    @Autowired lateinit var accounts: AccountRepository
+
     @Autowired lateinit var enrollments: EnrollmentRepository
 
     @Autowired lateinit var history: MembershipHistoryRepository
@@ -241,6 +247,51 @@ class GroupServiceIntegrationTest {
         assertTrue(skipped.message.contains("ACADEMIC_LEAVE"))
     }
 
+    @Test
+    fun `import reports occupied login with row and writes nothing`() {
+        accounts.saveAndFlush(
+            Account(
+                login = "3001",
+                passwordHash = "x",
+                role = LmsRole.STUDENT,
+                mustChangePassword = true,
+            ),
+        )
+        val result =
+            importService.import(
+                "group.csv",
+                csv("ПИ;1;9;БО;2026;Иванов Иван;3001;бюджет"),
+                null,
+            )
+
+        assertFalse(result.applied)
+        assertEquals(1, result.errors.size)
+        val error = result.errors.single()
+        assertEquals(2, error.row)
+        assertTrue(error.message.contains("Логин 3001"))
+        assertNull(students.findByStudentNo("3001"))
+    }
+
+    @Test
+    fun `import reports inactive target group and writes nothing`() {
+        val group = groupService.create(CreateGroupRequest(stream = "ПИ", course = 1, number = 8, degree = "БО", enrollmentYear = 2026))
+        groupService.archiveGroup(UUID.fromString(group.id))
+
+        val result =
+            importService.import(
+                "group.csv",
+                csv("ПИ;1;8;БО;2026;Иванов Иван;3002;бюджет"),
+                null,
+            )
+
+        assertFalse(result.applied)
+        assertEquals(1, result.errors.size)
+        val error = result.errors.single()
+        assertEquals(2, error.row)
+        assertTrue(error.message.contains("не активна"))
+        assertNull(students.findByStudentNo("3002"))
+    }
+
     @Test
     fun `import still updates an active student`() {
         importService.import("group.csv", csv(validRows()), null)