Expose list of error messages instead of single current

Updated tests to match

app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt

@@ -110,11 +110,13 @@ class NiaAppState(
             initialValue = false,
         )
 
-    val snackbarMessage = errorMessage.stateIn(
+    val snackbarMessage = errorMessages
-        scope = coroutineScope,
+        .map { it.firstOrNull() }
-        started = SharingStarted.WhileSubscribed(5_000),
+        .stateIn(
-        initialValue = null,
+            scope = coroutineScope,
-    )
+            started = SharingStarted.WhileSubscribed(5_000),
+            initialValue = null,
+        )
 
     /**
      * Map of top level destinations to be used in the TopBar, BottomBar and NavRail. The key is the

core/data-test/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/test/FakeErrorMonitor.kt

@@ -31,6 +31,6 @@ class FakeErrorMonitor @Inject constructor() : ErrorMonitor {
         // Do nothing
     }
 
-    override val errorMessage: Flow<ErrorMessage?>
+    override val errorMessages: Flow<List<ErrorMessage?>>
-        get() = flowOf(null)
+        get() = flowOf(emptyList())
 }

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/util/ErrorMonitor.kt

@@ -24,5 +24,5 @@ import kotlinx.coroutines.flow.Flow
 interface ErrorMonitor {
     fun addErrorMessage(error: String): String?
     fun clearErrorMessage(id: String)
-    val errorMessage: Flow<ErrorMessage?>
+    val errorMessages: Flow<List<ErrorMessage?>>
 }

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/util/SnackbarErrorMonitor.kt

@@ -18,7 +18,6 @@ package com.google.samples.apps.nowinandroid.core.data.util
 
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.update
 import java.util.UUID
 import javax.inject.Inject
@@ -31,12 +30,8 @@ class SnackbarErrorMonitor @Inject constructor() : ErrorMonitor {
     /**
      * List of [ErrorMessage] to be shown to the user, via Snackbar.
      */
-    private val errorMessages = MutableStateFlow<List<ErrorMessage>>(emptyList())
+    private val _errorMessages = MutableStateFlow<List<ErrorMessage>>(emptyList())
-
+    override val errorMessages: Flow<List<ErrorMessage>> = _errorMessages
-    /**
-     * Current [ErrorMessage] or null if there are none.
-     */
-    override val errorMessage: Flow<ErrorMessage?> = errorMessages.map { it.firstOrNull() }
 
     /**
      * Creates an [ErrorMessage] from String value and adds it to the list.
@@ -49,7 +44,7 @@ class SnackbarErrorMonitor @Inject constructor() : ErrorMonitor {
     override fun addErrorMessage(error: String): String? {
         if (error.isNotBlank()) {
             val newError = ErrorMessage(error)
-            errorMessages.update { it + newError }
+            _errorMessages.update { it + newError }
             return newError.id
         }
         return null
@@ -59,7 +54,7 @@ class SnackbarErrorMonitor @Inject constructor() : ErrorMonitor {
      * Removes the [ErrorMessage] with the specified [id] from the list.
      */
     override fun clearErrorMessage(id: String) {
-        errorMessages.update { it.filter { item -> item.id != id } }
+        _errorMessages.update { it.filter { item -> item.id != id } }
     }
 }
 

core/data/src/test/kotlin/com/google/samples/apps/nowinandroid/core/data/util/SnackbarErrorMonitorTest.kt

@@ -36,7 +36,7 @@ class SnackbarErrorMonitorTest {
 
     @Test
     fun whenErrorIsNotAdded_NullIsPresent() = runTest(UnconfinedTestDispatcher()) {
-        backgroundScope.launch { state.errorMessage.collect() }
+        backgroundScope.launch { state.errorMessages.collect() }
         assertEquals(
             null,
             message,
@@ -46,8 +46,8 @@ class SnackbarErrorMonitorTest {
     @Test
     fun whenErrorIsAdded_ErrorMessageIsPresent() = runTest(UnconfinedTestDispatcher()) {
         backgroundScope.launch {
-            state.errorMessage.collect {
+            state.errorMessages.collect {
-                message = it
+                message = it.firstOrNull()
             }
         }
 
@@ -66,8 +66,8 @@ class SnackbarErrorMonitorTest {
             state.addErrorMessage("Test Error Message 2")
 
             backgroundScope.launch {
-                state.errorMessage.collect {
+                state.errorMessages.collect {
-                    message = it
+                    message = it.firstOrNull()
                 }
             }
 
@@ -81,8 +81,8 @@ class SnackbarErrorMonitorTest {
     fun whenErrorIsCleared_ErrorMessageIsNotPresent() =
         runTest(UnconfinedTestDispatcher()) {
             backgroundScope.launch {
-                state.errorMessage.collect {
+                state.errorMessages.collect {
-                    message = it
+                    message = it.firstOrNull()
                 }
             }
             val id = state.addErrorMessage("Test Error Message 1")
@@ -99,8 +99,8 @@ class SnackbarErrorMonitorTest {
     fun whenErrorsAreCleared_NextErrorMessageIsPresent() =
         runTest(UnconfinedTestDispatcher()) {
             backgroundScope.launch {
-                state.errorMessage.collect {
+                state.errorMessages.collect {
-                    message = it
+                    message = it.firstOrNull()
                 }
             }
             val id1 = state.addErrorMessage("Test Error Message 1")

core/testing/src/main/kotlin/com/google/samples/apps/nowinandroid/core/testing/util/TestErrorMonitor.kt

@@ -30,6 +30,6 @@ class TestErrorMonitor : ErrorMonitor {
         // Do nothing
     }
 
-    override val errorMessage: Flow<ErrorMessage?>
+    override val errorMessages: Flow<List<ErrorMessage?>>
-        get() = flowOf(ErrorMessage("Error Message", "1"))
+        get() = flowOf(listOf(ErrorMessage("Error Message", "1")))
 }