Apply flowOn(defaultDispatchers) for main-safe.

app/src/androidTest/kotlin/com/google/samples/apps/nowinandroid/ui/NavigationUiTest.kt

@@ -37,6 +37,7 @@ import com.google.samples.apps.nowinandroid.uitesthiltmanifest.HiltComponentActi
 import dagger.hilt.android.testing.BindValue
 import dagger.hilt.android.testing.HiltAndroidRule
 import dagger.hilt.android.testing.HiltAndroidTest
+import kotlinx.coroutines.Dispatchers
 import org.junit.Before
 import org.junit.Rule
 import org.junit.Test
@@ -79,6 +80,7 @@ class NavigationUiTest {
     val userNewsResourceRepository = CompositeUserNewsResourceRepository(
         newsRepository = TestNewsRepository(),
         userDataRepository = TestUserDataRepository(),
+        defaultDispatcher = Dispatchers.Default,
     )
 
     @Inject

app/src/androidTest/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppStateTest.kt

@@ -35,6 +35,7 @@ import com.google.samples.apps.nowinandroid.core.testing.repository.TestNewsRepo
 import com.google.samples.apps.nowinandroid.core.testing.repository.TestUserDataRepository
 import com.google.samples.apps.nowinandroid.core.testing.util.TestNetworkMonitor
 import com.google.samples.apps.nowinandroid.core.testing.util.TestTimeZoneMonitor
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.test.UnconfinedTestDispatcher
@@ -64,7 +65,7 @@ class NiaAppStateTest {
     private val timeZoneMonitor = TestTimeZoneMonitor()
 
     private val userNewsResourceRepository =
-        CompositeUserNewsResourceRepository(TestNewsRepository(), TestUserDataRepository())
+        CompositeUserNewsResourceRepository(TestNewsRepository(), TestUserDataRepository(), Dispatchers.Default)
 
     // Subject under test.
     private lateinit var state: NiaAppState

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/repository/CompositeUserNewsResourceRepository.kt

@@ -18,11 +18,15 @@ package com.google.samples.apps.nowinandroid.core.data.repository
 
 import com.google.samples.apps.nowinandroid.core.model.data.UserNewsResource
 import com.google.samples.apps.nowinandroid.core.model.data.mapToUserNewsResources
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.Default
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.map
 import javax.inject.Inject
 
@@ -33,6 +37,7 @@ import javax.inject.Inject
 class CompositeUserNewsResourceRepository @Inject constructor(
     val newsRepository: NewsRepository,
     val userDataRepository: UserDataRepository,
+    @Dispatcher(Default) private val defaultDispatcher: CoroutineDispatcher,
 ) : UserNewsResourceRepository {
 
     /**
@@ -43,8 +48,10 @@ class CompositeUserNewsResourceRepository @Inject constructor(
     ): Flow<List<UserNewsResource>> =
         newsRepository.getNewsResources(query)
             .combine(userDataRepository.userData) { newsResources, userData ->
-                newsResources.mapToUserNewsResources(userData)
-            }
+                    newsResources.mapToUserNewsResources(userData)
+            }.flowOn(
+                defaultDispatcher
+            )
 
     /**
      * Returns available news resources (joined with user data) for the followed topics.

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/repository/DefaultSearchContentsRepository.kt

@@ -25,13 +25,15 @@ import com.google.samples.apps.nowinandroid.core.database.model.asExternalModel
 import com.google.samples.apps.nowinandroid.core.database.model.asFtsEntity
 import com.google.samples.apps.nowinandroid.core.model.data.SearchResult
 import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.Default
 import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.mapLatest
 import kotlinx.coroutines.withContext
 import javax.inject.Inject
@@ -42,6 +44,7 @@ internal class DefaultSearchContentsRepository @Inject constructor(
     private val topicDao: TopicDao,
     private val topicFtsDao: TopicFtsDao,
     @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
+    @Dispatcher(Default) private val defaultDispatcher: CoroutineDispatcher,
 ) : SearchContentsRepository {
 
     override suspend fun populateFtsData() {
@@ -79,7 +82,7 @@ internal class DefaultSearchContentsRepository @Inject constructor(
                 topics = topics.map { it.asExternalModel() },
                 newsResources = newsResources.map { it.asExternalModel() },
             )
-        }
+        }.flowOn(defaultDispatcher)
     }
 
     override fun getSearchContentsCount(): Flow<Int> =
@@ -88,5 +91,5 @@ internal class DefaultSearchContentsRepository @Inject constructor(
             topicFtsDao.getCount(),
         ) { newsResourceCount, topicsCount ->
             newsResourceCount + topicsCount
-        }
+        }.flowOn(defaultDispatcher)
 }

core/domain/src/main/kotlin/com/google/samples/apps/nowinandroid/core/domain/GetFollowableTopicsUseCase.kt

@@ -21,8 +21,12 @@ import com.google.samples.apps.nowinandroid.core.data.repository.UserDataReposit
 import com.google.samples.apps.nowinandroid.core.domain.TopicSortField.NAME
 import com.google.samples.apps.nowinandroid.core.domain.TopicSortField.NONE
 import com.google.samples.apps.nowinandroid.core.model.data.FollowableTopic
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.Default
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flowOn
 import javax.inject.Inject
 
 /**
@@ -31,6 +35,7 @@ import javax.inject.Inject
 class GetFollowableTopicsUseCase @Inject constructor(
     private val topicsRepository: TopicsRepository,
     private val userDataRepository: UserDataRepository,
+    @Dispatcher(Default) private val defaultDispatcher: CoroutineDispatcher,
 ) {
     /**
      * Returns a list of topics with their associated followed state.
@@ -52,7 +57,7 @@ class GetFollowableTopicsUseCase @Inject constructor(
             NAME -> followedTopics.sortedBy { it.topic.name }
             else -> followedTopics
         }
-    }
+    }.flowOn(defaultDispatcher)
 }
 
 enum class TopicSortField {

core/domain/src/main/kotlin/com/google/samples/apps/nowinandroid/core/domain/GetSearchContentsUseCase.kt

@@ -23,8 +23,12 @@ import com.google.samples.apps.nowinandroid.core.model.data.SearchResult
 import com.google.samples.apps.nowinandroid.core.model.data.UserData
 import com.google.samples.apps.nowinandroid.core.model.data.UserNewsResource
 import com.google.samples.apps.nowinandroid.core.model.data.UserSearchResult
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.Default
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flowOn
 import javax.inject.Inject
 
 /**
@@ -33,16 +37,20 @@ import javax.inject.Inject
 class GetSearchContentsUseCase @Inject constructor(
     private val searchContentsRepository: SearchContentsRepository,
     private val userDataRepository: UserDataRepository,
+    @Dispatcher(Default) private val defaultDispatcher: CoroutineDispatcher,
 ) {
 
     operator fun invoke(
         searchQuery: String,
     ): Flow<UserSearchResult> =
         searchContentsRepository.searchContents(searchQuery)
-            .mapToUserSearchResult(userDataRepository.userData)
+            .mapToUserSearchResult(userDataRepository.userData, defaultDispatcher)
 }
 
-private fun Flow<SearchResult>.mapToUserSearchResult(userDataStream: Flow<UserData>): Flow<UserSearchResult> =
+private fun Flow<SearchResult>.mapToUserSearchResult(
+    userDataStream: Flow<UserData>,
+    defaultDispatcher: CoroutineDispatcher,
+): Flow<UserSearchResult> =
     combine(userDataStream) { searchResult, userData ->
         UserSearchResult(
             topics = searchResult.topics.map { topic ->
@@ -58,4 +66,4 @@ private fun Flow<SearchResult>.mapToUserSearchResult(userDataStream: Flow<UserDa
                 )
             },
         )
-    }
+    }.flowOn(defaultDispatcher)

feature/search/src/test/kotlin/com/google/samples/apps/nowinandroid/feature/search/SearchViewModelTest.kt

@@ -32,6 +32,7 @@ import com.google.samples.apps.nowinandroid.feature.search.RecentSearchQueriesUi
 import com.google.samples.apps.nowinandroid.feature.search.SearchResultUiState.EmptyQuery
 import com.google.samples.apps.nowinandroid.feature.search.SearchResultUiState.Loading
 import com.google.samples.apps.nowinandroid.feature.search.SearchResultUiState.SearchNotReady
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.test.UnconfinedTestDispatcher
@@ -56,6 +57,7 @@ class SearchViewModelTest {
     private val getSearchContentsUseCase = GetSearchContentsUseCase(
         searchContentsRepository = searchContentsRepository,
         userDataRepository = userDataRepository,
+        defaultDispatcher = Dispatchers.Default
     )
     private val recentSearchRepository = TestRecentSearchRepository()
     private val getRecentQueryUseCase = GetRecentSearchQueriesUseCase(recentSearchRepository)

feature/topic/src/test/kotlin/com/google/samples/apps/nowinandroid/feature/topic/TopicViewModelTest.kt

@@ -26,6 +26,7 @@ import com.google.samples.apps.nowinandroid.core.testing.repository.TestTopicsRe
 import com.google.samples.apps.nowinandroid.core.testing.repository.TestUserDataRepository
 import com.google.samples.apps.nowinandroid.core.testing.util.MainDispatcherRule
 import com.google.samples.apps.nowinandroid.feature.topic.navigation.TOPIC_ID_ARG
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.first
@@ -54,6 +55,7 @@ class TopicViewModelTest {
     private val userNewsResourceRepository = CompositeUserNewsResourceRepository(
         newsRepository = newsRepository,
         userDataRepository = userDataRepository,
+        defaultDispatcher = Dispatchers.Default,
     )
     private lateinit var viewModel: TopicViewModel