[POC] refactor: context receivers

build.gradle.kts

@@ -157,6 +157,7 @@ allprojects {
     kotlinOptions {
       val version = JavaVersion.VERSION_11.toString()
       jvmTarget = version
+      freeCompilerArgs = freeCompilerArgs + "-Xcontext-receivers"
     }
   }
 

data/src/main/java/com/hoc/flowmvi/data/UserRepositoryImpl.kt

@@ -2,10 +2,11 @@
 
 import arrow.core.Either.Companion.catch as catchEither
 import arrow.core.ValidatedNel
-import arrow.core.continuations.either
+import arrow.core.continuations.EffectScope
 import arrow.core.left
 import arrow.core.leftWiden
 import arrow.core.right
+import arrow.core.traverse
 import arrow.core.valueOr
 import com.hoc.flowmvi.core.Mapper
 import com.hoc.flowmvi.core.dispatchers.AppCoroutineDispatchers
@@ -16,6 +17,7 @@
 import com.hoc.flowmvi.domain.model.UserError
 import com.hoc.flowmvi.domain.model.UserValidationError
 import com.hoc.flowmvi.domain.repository.UserRepository
+import com.hoc081098.flowext.flowFromSuspend
 import com.hoc081098.flowext.retryWithExponentialBackoff
 import java.io.IOException
 import kotlin.time.Duration.Companion.milliseconds
@@ -24,7 +26,6 @@
 import kotlinx.coroutines.FlowPreview
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
-import kotlinx.coroutines.flow.asFlow
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flatMapConcat
@@ -51,34 +52,28 @@
     class Added(val user: User) : Change()
   }
 
-  private val responseToDomainThrows: (UserResponse) -> User = { response ->
-    responseToDomain(response).let { validated ->
-      validated.valueOr {
-        val t = UserError.ValidationFailed(it.toSet())
-        logError(t, "Map $response to user")
-        throw t
-      }
-    }
-  }
-
   private val changesFlow = MutableSharedFlow<Change>(extraBufferCapacity = 64)
-
   private suspend inline fun sendChange(change: Change) = changesFlow.emit(change)
 
-  @Suppress("NOTHING_TO_INLINE")
-  private inline fun logError(t: Throwable, message: String) = Timber.tag(TAG).e(t, message)
-
-  private fun getUsersFromRemote(): Flow<List<User>> = suspend {
+  private fun getUsersFromRemote(): Flow<List<User>> = flowFromSuspend {
     Timber.d("[USER_REPO] getUsersFromRemote ...")
+
     userApiService
       .getUsers()
-      .map(responseToDomainThrows)
-  }.asFlow()
-    .retryWithExponentialBackoff(
-      maxAttempt = 2,
-      initialDelay = 500.milliseconds,
-      factor = 2.0,
-    ) { it is IOException }
+      .let { response ->
+        response
+          .traverse(responseToDomain)
+          .valueOr { validationErrors ->
+            throw UserError.ValidationFailed(validationErrors.toSet()).also {
+              logError(it, "Failed to map $response to user")
+            }
+          }
+      }
+  }.retryWithExponentialBackoff(
+    maxAttempt = 2,
+    initialDelay = 500.milliseconds,
+    factor = 2.0,
+  ) { it is IOException }
 
   override fun getUsers() = getUsersFromRemote()
     .flatMapConcat { initial ->
@@ -99,13 +94,16 @@
       emit(errorMapper(it).left())
     }
 
+  context(EffectScope<UserError>)
   override suspend fun refresh() = catchEither { getUsersFromRemote().first() }
     .tap { sendChange(Change.Refreshed(it)) }
     .map { }
     .tapLeft { logError(it, "refresh") }
     .mapLeft(errorMapper)
+    .bind()
 
-  override suspend fun remove(user: User) = either<UserError, Unit> {
+  context(EffectScope<UserError>)
+  override suspend fun remove(user: User) {
     withContext(dispatchers.io) {
       val response = catchEither { userApiService.remove(user.id) }
         .tapLeft { logError(it, "remove user=$user") }
@@ -121,7 +119,8 @@
     }
   }
 
-  override suspend fun add(user: User) = either<UserError, Unit> {
+  context(EffectScope<UserError>)
+  override suspend fun add(user: User) {
     withContext(dispatchers.io) {
       val response = catchEither { userApiService.add(domainToBody(user)) }
         .tapLeft { logError(it, "add user=$user") }
@@ -137,13 +136,30 @@
     }
   }
 
+  context(EffectScope<UserError>)
   override suspend fun search(query: String) = withContext(dispatchers.io) {
-    catchEither { userApiService.search(query).map(responseToDomainThrows) }
+    val userResponses = catchEither { userApiService.search(query) }
       .tapLeft { logError(it, "search query=$query") }
       .mapLeft(errorMapper)
+      .bind()
+
+    val users = userResponses.traverse(responseToDomain)
+      .mapLeft { UserError.ValidationFailed(it.toSet()) }
+      .tapInvalid {
+        logError(
+          it,
+          "search query=$query, failed to map $userResponses to List<User>"
+        )
+      }
+      .bind()
+
+    users
   }
 
   private companion object {
     private val TAG = UserRepositoryImpl::class.java.simpleName
+
+    @Suppress("NOTHING_TO_INLINE")
+    private inline fun logError(t: Throwable, message: String) = Timber.tag(TAG).e(t, message)
   }
 }

data/src/test/java/com/hoc/flowmvi/data/UserRepositoryImplTest.kt

@@ -2,6 +2,7 @@ package com.hoc.flowmvi.data
 
 import arrow.core.Either
 import arrow.core.ValidatedNel
+import arrow.core.continuations.either
 import arrow.core.validNel
 import com.hoc.flowmvi.core.Mapper
 import com.hoc.flowmvi.data.remote.UserApiService
@@ -144,7 +145,7 @@ class UserRepositoryImplTest {
     coEvery { userApiService.getUsers() } returns USER_RESPONSES
     every { responseToDomain(any()) } returnsMany VALID_NEL_USERS
 
-    val result = repo.refresh()
+    val result = either { repo.refresh() }
 
     assertTrue(result.isRight())
     assertNotNull(result.orNull())
@@ -163,7 +164,7 @@ class UserRepositoryImplTest {
     coEvery { userApiService.getUsers() } throws ioException
     every { errorMapper(ofType<IOException>()) } returns UserError.NetworkError
 
-    val result = repo.refresh()
+    val result = either { repo.refresh() }
 
     assertTrue(result.isLeft())
     assertEquals(UserError.NetworkError, result.leftOrThrow)
@@ -179,7 +180,7 @@ class UserRepositoryImplTest {
     coEvery { userApiService.remove(user.id) } returns userResponse
     every { responseToDomain(userResponse) } returns user.validNel()
 
-    val result = repo.remove(user)
+    val result = either { repo.remove(user) }
 
     assertTrue(result.isRight())
     assertNotNull(result.orNull())
@@ -194,7 +195,7 @@ class UserRepositoryImplTest {
     coEvery { userApiService.remove(user.id) } throws IOException()
     every { errorMapper(ofType<IOException>()) } returns UserError.NetworkError
 
-    val result = repo.remove(user)
+    val result = either { repo.remove(user) }
 
     assertTrue(result.isLeft())
     assertEquals(UserError.NetworkError, result.leftOrThrow)
@@ -211,7 +212,7 @@ class UserRepositoryImplTest {
     every { domainToBody(user) } returns USER_BODY
     every { responseToDomain(userResponse) } returns user.validNel()
 
-    val result = repo.add(user)
+    val result = either { repo.add(user) }
 
     assertTrue(result.isRight())
     assertNotNull(result.orNull())
@@ -228,7 +229,7 @@ class UserRepositoryImplTest {
     every { domainToBody(user) } returns USER_BODY
     every { errorMapper(ofType<IOException>()) } returns UserError.NetworkError
 
-    val result = repo.add(user)
+    val result = either { repo.add(user) }
 
     assertTrue(result.isLeft())
     assertEquals(UserError.NetworkError, result.leftOrThrow)
@@ -244,7 +245,7 @@ class UserRepositoryImplTest {
     coEvery { userApiService.search(q) } returns USER_RESPONSES
     every { responseToDomain(any()) } returnsMany VALID_NEL_USERS
 
-    val result = repo.search(q)
+    val result = either { repo.search(q) }
 
     assertTrue(result.isRight())
     assertNotNull(result.orNull())
@@ -264,7 +265,7 @@ class UserRepositoryImplTest {
     coEvery { userApiService.search(q) } throws IOException()
     every { errorMapper(ofType<IOException>()) } returns UserError.NetworkError
 
-    val result = repo.search(q)
+    val result = either { repo.search(q) }
 
     assertTrue(result.isLeft())
     assertEquals(UserError.NetworkError, result.leftOrThrow)
@@ -337,8 +338,10 @@ class UserRepositoryImplTest {
       val job = launch(start = CoroutineStart.UNDISPATCHED) {
         repo.getUsers().toList(events)
       }
-      repo.add(user)
-      repo.remove(user)
+      either {
+        repo.add(user)
+        repo.remove(user)
+      }.getOrThrow
       delay(120_000)
       job.cancel()
 

domain/src/main/java/com/hoc/flowmvi/domain/repository/UserRepository.kt

@@ -1,18 +1,23 @@
 package com.hoc.flowmvi.domain.repository
 
 import arrow.core.Either
+import arrow.core.continuations.EffectScope
 import com.hoc.flowmvi.domain.model.User
 import com.hoc.flowmvi.domain.model.UserError
 import kotlinx.coroutines.flow.Flow
 
 interface UserRepository {
   fun getUsers(): Flow<Either<UserError, List<User>>>
 
-  suspend fun refresh(): Either<UserError, Unit>
+  context(EffectScope<UserError>)
+  suspend fun refresh()
 
-  suspend fun remove(user: User): Either<UserError, Unit>
+  context(EffectScope<UserError>)
+  suspend fun remove(user: User)
 
-  suspend fun add(user: User): Either<UserError, Unit>
+  context(EffectScope<UserError>)
+  suspend fun add(user: User)
 
-  suspend fun search(query: String): Either<UserError, List<User>>
+  context(EffectScope<UserError>)
+  suspend fun search(query: String): List<User>
 }

domain/src/main/java/com/hoc/flowmvi/domain/usecase/AddUserUseCase.kt

@@ -1,10 +1,11 @@
 package com.hoc.flowmvi.domain.usecase
 
-import arrow.core.Either
+import arrow.core.continuations.EffectScope
 import com.hoc.flowmvi.domain.model.User
 import com.hoc.flowmvi.domain.model.UserError
 import com.hoc.flowmvi.domain.repository.UserRepository
 
 class AddUserUseCase(private val userRepository: UserRepository) {
-  suspend operator fun invoke(user: User): Either<UserError, Unit> = userRepository.add(user)
+  context(EffectScope<UserError>)
+  suspend operator fun invoke(user: User): Unit = userRepository.add(user)
 }

domain/src/main/java/com/hoc/flowmvi/domain/usecase/RefreshGetUsersUseCase.kt

@@ -1,9 +1,10 @@
 package com.hoc.flowmvi.domain.usecase
 
-import arrow.core.Either
+import arrow.core.continuations.EffectScope
 import com.hoc.flowmvi.domain.model.UserError
 import com.hoc.flowmvi.domain.repository.UserRepository
 
 class RefreshGetUsersUseCase(private val userRepository: UserRepository) {
-  suspend operator fun invoke(): Either<UserError, Unit> = userRepository.refresh()
+  context(EffectScope<UserError>)
+  suspend operator fun invoke(): Unit = userRepository.refresh()
 }

domain/src/main/java/com/hoc/flowmvi/domain/usecase/RemoveUserUseCase.kt

@@ -1,10 +1,11 @@
 package com.hoc.flowmvi.domain.usecase
 
-import arrow.core.Either
+import arrow.core.continuations.EffectScope
 import com.hoc.flowmvi.domain.model.User
 import com.hoc.flowmvi.domain.model.UserError
 import com.hoc.flowmvi.domain.repository.UserRepository
 
 class RemoveUserUseCase(private val userRepository: UserRepository) {
-  suspend operator fun invoke(user: User): Either<UserError, Unit> = userRepository.remove(user)
+  context(EffectScope<UserError>)
+  suspend operator fun invoke(user: User): Unit = userRepository.remove(user)
 }

domain/src/main/java/com/hoc/flowmvi/domain/usecase/SearchUsersUseCase.kt

@@ -1,11 +1,12 @@
 package com.hoc.flowmvi.domain.usecase
 
-import arrow.core.Either
+import arrow.core.continuations.EffectScope
 import com.hoc.flowmvi.domain.model.User
 import com.hoc.flowmvi.domain.model.UserError
 import com.hoc.flowmvi.domain.repository.UserRepository
 
 class SearchUsersUseCase(private val userRepository: UserRepository) {
-  suspend operator fun invoke(query: String): Either<UserError, List<User>> =
+  context(EffectScope<UserError>)
+  suspend operator fun invoke(query: String): List<User> =
     userRepository.search(query)
 }