refactor: drop null handling the compiler now proves redundant

Kotlin 2.2 propagates nullability further, so a number of safe calls, !!
assertions, elvis fallbacks and casts are now provably dead. Two of these
hid real problems: MimeMessageParser pinned JavaMail platform types to
non-null, which silently disabled its null checks even though getRecipients
and getFrom do return null, and ValidationError cast a vararg Array<out
String> to Array<String>.

Author: bdshadow

backend/api/src/main/kotlin/io/tolgee/hateoas/invitation/OrganizationInvitationModelAssembler.kt

@@ -18,7 +18,7 @@ class OrganizationInvitationModelAssembler(
     return OrganizationInvitationModel(
       entity.id!!,
       entity.code,
-      entity.organizationRole!!.type!!,
+      entity.organizationRole!!.type,
       entity.createdAt!!,
       invitedUserName = entity.name,
       invitedUserEmail = entity.email,

backend/api/src/main/kotlin/io/tolgee/hateoas/organization/SimpleOrganizationModelAssembler.kt

@@ -17,7 +17,7 @@ class SimpleOrganizationModelAssembler(
     SimpleOrganizationModel::class.java,
   ) {
   override fun toModel(entity: Organization): SimpleOrganizationModel {
-    val link = linkTo<OrganizationController> { get(entity.slug ?: "") }.withSelfRel()
+    val link = linkTo<OrganizationController> { get(entity.slug) }.withSelfRel()
     return SimpleOrganizationModel(
       entity.id,
       entity.name,

backend/api/src/main/kotlin/io/tolgee/hateoas/translations/suggestions/TranslationSuggestionModelAssembler.kt

@@ -18,7 +18,7 @@ class TranslationSuggestionModelAssembler(
     return TranslationSuggestionModel(
       id = entity.id,
       languageId = entity.language!!.id,
-      keyId = entity.key!!.id,
+      keyId = entity.key.id,
       translation = entity.translation,
       author = simpleUserAccountModelAssembler.toModel(entity.author!!),
       state = entity.state,

backend/app/src/main/kotlin/io/tolgee/ExceptionHandlers.kt

@@ -69,7 +69,7 @@ class ExceptionHandlers : Logging {
   @ExceptionHandler(MethodArgumentTypeMismatchException::class)
   fun handleValidationExceptions(ex: MethodArgumentTypeMismatchException): ResponseEntity<ErrorResponseBody> {
     return ResponseEntity(
-      ErrorResponseBody(Message.WRONG_PARAM_TYPE.code, listOf(ex.parameter.parameterName) as List<Serializable>?),
+      ErrorResponseBody(Message.WRONG_PARAM_TYPE.code, listOfNotNull(ex.parameter.parameterName)),
       HttpStatus.BAD_REQUEST,
     )
   }

backend/app/src/test/kotlin/io/tolgee/api/v2/controllers/translations/v2TranslationsController/TranslationsControllerHistoryTest.kt

@@ -119,7 +119,7 @@ class TranslationsControllerHistoryTest : ProjectAuthControllerTest("/v2/project
         translationService.find(emptyKey, lang).get()
       }
 
-    performProjectAuthGet("/translations/${translation!!.id}/history").andPrettyPrint.andAssertThatJson {
+    performProjectAuthGet("/translations/${translation.id}/history").andPrettyPrint.andAssertThatJson {
       node("page.totalElements").isEqualTo(0)
     }
   }

backend/app/src/test/kotlin/io/tolgee/api/v2/controllers/v2ImportController/V2ImportControllerAddFilesTest.kt

@@ -232,9 +232,8 @@ class V2ImportControllerAddFilesTest : ProjectAuthControllerTest("/v2/projects/"
         assertThat(
           it.files[0]
             .issues[0]
-            .params
-            ?.get(0)
-            ?.value,
+            .params[0]
+            .value,
         ).isEqualTo("too_long")
       }
     }

backend/app/src/test/kotlin/io/tolgee/api/v2/controllers/v2ProjectsController/ProjectsControllerTest.kt

@@ -219,7 +219,7 @@ class ProjectsControllerTest : ProjectAuthControllerTest("/v2/projects/") {
     val usersAndOrganizations = dbPopulator.createUsersAndOrganizations()
     val repo = usersAndOrganizations[1].organizationRoles[0].organization!!.projects[0]
     val user = dbPopulator.createUserIfNotExists("jirina")
-    organizationRoleService.grantOwnerRoleToUser(user, repo.organizationOwner!!)
+    organizationRoleService.grantOwnerRoleToUser(user, repo.organizationOwner)
 
     loginAsUser(usersAndOrganizations[1].name)
 

backend/app/src/test/kotlin/io/tolgee/batch/AbstractBatchJobsGeneralTest.kt

@@ -402,7 +402,7 @@ abstract class AbstractBatchJobsGeneralTest :
 
     executions
       .last()
-      .successTargets!!
+      .successTargets
       .assert
       .size()
       .isEqualTo(2) // 2 failed items in a chunk are retried successfully

backend/app/src/test/kotlin/io/tolgee/controllers/ExportControllerTest.kt

@@ -29,7 +29,6 @@ import java.time.ZonedDateTime
 import java.time.format.DateTimeFormatter
 import java.util.Date
 import java.util.function.Consumer
-import java.util.zip.ZipEntry
 import java.util.zip.ZipInputStream
 
 @AutoConfigureMockMvc
@@ -191,12 +190,9 @@ class ExportControllerTest : ProjectAuthControllerTest() {
     val byteArrayInputStream = ByteArrayInputStream(responseContent)
     val zipInputStream = ZipInputStream(byteArrayInputStream)
     val result = HashMap<String, Long>()
-    var nextEntry: ZipEntry?
-    while (zipInputStream.nextEntry.also {
-        nextEntry = it
-      } != null
-    ) {
-      result[nextEntry!!.name] = nextEntry!!.size
+    while (true) {
+      val nextEntry = zipInputStream.nextEntry ?: break
+      result[nextEntry.name] = nextEntry.size
     }
     return result
   }

backend/app/src/test/kotlin/io/tolgee/repository/ProjectRepositoryTest.kt

@@ -60,7 +60,7 @@ class ProjectRepositoryTest {
         filters = ProjectFilters(),
       )
     assertThat(result).hasSize(10)
-    assertThat(result.content[0].organizationOwner?.name).isNotNull
-    assertThat(result.content[8].organizationOwner?.slug).isNotNull
+    assertThat(result.content[0].organizationOwner.name).isNotNull
+    assertThat(result.content[8].organizationOwner.slug).isNotNull
   }
 }