REDI-98: error-handling demo screen (DataError -> UiText pipeline)

A runnable MVI screen (reached from the list overflow menu) that forces a real DataError.Network case and routes it through the same pipeline a genuine call uses: Result.Error -> onFailure -> DataError.toUiText() -> design-system ErrorState. Three distinct cases (NO_INTERNET, NOT_FOUND, SERVER_ERROR) each render their mapped message; Retry re-issues the last attempt via an Action; a successful load clears the error. Wired as intra-feature navigation (ErrorDemoRoute) and registered in Koin (incl. the UseCase factoryOf).
2026-06-10 15:00:27 +02:00
parent 0542d4dc1d
commit cf63095acc
9 changed files with 338 additions and 6 deletions
--- a/feature/characters/presentation-compose/src/main/kotlin/com/example/architecture/feature/characters/presentation/compose/CharacterListScreen.kt
+++ b/feature/characters/presentation-compose/src/main/kotlin/com/example/architecture/feature/characters/presentation/compose/CharacterListScreen.kt
@@ -66,14 +66,15 @@ import org.koin.androidx.compose.koinViewModel
 * Root: owns the ViewModel (via Koin), observes one-time Events, and forwards navigation up.
 * The snackbar is resolved with the Context-based [asString] because it runs outside composition.
 *
- * [onOpenAbout] and [onOpenViewsList] are renderer-only chrome (a Compose overflow menu), so they
- * are plain callbacks rather than going through the shared, UI-agnostic ViewModel.
+ * [onOpenAbout], [onOpenViewsList] and [onOpenErrorDemo] are renderer-only chrome (a Compose overflow
+ * menu), so they are plain callbacks rather than going through the shared, UI-agnostic ViewModel.
 */
@Composable
 fun CharacterListRoot(
    onCharacterClick: (Int) -> Unit,
    onOpenAbout: () -> Unit,
    onOpenViewsList: () -> Unit,
+    onOpenErrorDemo: () -> Unit,
    viewModel: CharacterListViewModel = koinViewModel(),
 ) {
    val state by viewModel.state.collectAsStateWithLifecycle()
@@ -95,6 +96,7 @@ fun CharacterListRoot(
        onAction = viewModel::onAction,
        onOpenAbout = onOpenAbout,
        onOpenViewsList = onOpenViewsList,
+        onOpenErrorDemo = onOpenErrorDemo,
        snackbarHostState = snackbarHostState,
    )
 }
@@ -107,13 +109,20 @@ fun CharacterListScreen(
    onAction: (CharacterListAction) -> Unit,
    onOpenAbout: () -> Unit,
    onOpenViewsList: () -> Unit,
+    onOpenErrorDemo: () -> Unit,
    snackbarHostState: SnackbarHostState = remember { SnackbarHostState() },
 ) {
    AppScaffold(
        topBar = {
            TopAppBar(
                title = { Text(stringResource(R.string.characters_title)) },
-                actions = { CharacterListOverflowMenu(onOpenAbout = onOpenAbout, onOpenViewsList = onOpenViewsList) },
+                actions = {
+                    CharacterListOverflowMenu(
+                        onOpenAbout = onOpenAbout,
+                        onOpenViewsList = onOpenViewsList,
+                        onOpenErrorDemo = onOpenErrorDemo,
+                    )
+                },
            )
        },
    ) { innerPadding ->
@@ -149,6 +158,7 @@ fun CharacterListScreen(
 private fun CharacterListOverflowMenu(
    onOpenAbout: () -> Unit,
    onOpenViewsList: () -> Unit,
+    onOpenErrorDemo: () -> Unit,
 ) {
    var expanded by remember { mutableStateOf(false) }
    IconButton(onClick = { expanded = true }) {
@@ -165,6 +175,13 @@ private fun CharacterListOverflowMenu(
                onOpenViewsList()
            },
        )
+        DropdownMenuItem(
+            text = { Text(stringResource(R.string.menu_error_demo)) },
+            onClick = {
+                expanded = false
+                onOpenErrorDemo()
+            },
+        )
        DropdownMenuItem(
            text = { Text(stringResource(R.string.menu_about)) },
            onClick = {
@@ -284,6 +301,7 @@ private fun CharacterListScreenLoadedPreview() {
            onAction = {},
            onOpenAbout = {},
            onOpenViewsList = {},
+            onOpenErrorDemo = {},
        )
    }
 }
@@ -301,6 +319,7 @@ private fun CharacterListScreenErrorPreview() {
            onAction = {},
            onOpenAbout = {},
            onOpenViewsList = {},
+            onOpenErrorDemo = {},
        )
    }
 }
--- a/feature/characters/presentation-compose/src/main/kotlin/com/example/architecture/feature/characters/presentation/compose/CharactersNavigation.kt
+++ b/feature/characters/presentation-compose/src/main/kotlin/com/example/architecture/feature/characters/presentation/compose/CharactersNavigation.kt
@@ -13,10 +13,14 @@ data object CharacterListRoute
@Serializable
 data class CharacterDetailRoute(val characterId: Int)

+/** Type-safe route for the error-handling demo screen. */
+@Serializable
+data object ErrorDemoRoute
+
 /**
- * The characters feature nav graph. List→detail is intra-feature navigation, so it is driven by the
- * [navController] passed in. Cross-boundary destinations (the About screen, the Views renderer hosted
- * by `:app`) stay decoupled as callbacks supplied by `:app`.
+ * The characters feature nav graph. List→detail and list→error-demo are intra-feature navigation, so
+ * they are driven by the [navController] passed in. Cross-boundary destinations (the About screen,
+ * the Views renderer hosted by `:app`) stay decoupled as callbacks supplied by `:app`.
 */
 fun NavGraphBuilder.charactersGraph(
    navController: NavController,
@@ -30,6 +34,7 @@ fun NavGraphBuilder.charactersGraph(
            },
            onOpenAbout = onOpenAbout,
            onOpenViewsList = onOpenViewsList,
+            onOpenErrorDemo = { navController.navigate(ErrorDemoRoute) },
        )
    }
    composable<CharacterDetailRoute> {
@@ -38,4 +43,7 @@ fun NavGraphBuilder.charactersGraph(
        // CharacterDetailViewModel reads it (keeping that module free of any navigation dependency).
        CharacterDetailRoot(onNavigateBack = { navController.popBackStack() })
    }
+    composable<ErrorDemoRoute> {
+        ErrorDemoRoot(onNavigateBack = { navController.popBackStack() })
+    }
 }
--- a/feature/characters/presentation-compose/src/main/kotlin/com/example/architecture/feature/characters/presentation/compose/ErrorDemoScreen.kt
+++ b/feature/characters/presentation-compose/src/main/kotlin/com/example/architecture/feature/characters/presentation/compose/ErrorDemoScreen.kt
@@ -0,0 +1,156 @@
+package com.example.architecture.feature.characters.presentation.compose
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material3.Button
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.example.architecture.core.design.system.component.AppScaffold
+import com.example.architecture.core.design.system.component.ErrorState
+import com.example.architecture.core.design.system.component.LoadingIndicator
+import com.example.architecture.core.design.system.theme.AppTheme
+import com.example.architecture.core.presentation.ObserveAsEvents
+import com.example.architecture.core.presentation.asString
+import com.example.architecture.feature.characters.presentation.ErrorDemoAction
+import com.example.architecture.feature.characters.presentation.ErrorDemoEvent
+import com.example.architecture.feature.characters.presentation.ErrorDemoState
+import com.example.architecture.feature.characters.presentation.ErrorDemoViewModel
+import com.example.architecture.feature.characters.presentation.ErrorScenario
+import org.koin.androidx.compose.koinViewModel
+
+/**
+ * Root: owns the demo ViewModel (Koin) and forwards the one-time NavigateBack event up the stack.
+ */
+@Composable
+fun ErrorDemoRoot(
+    onNavigateBack: () -> Unit,
+    viewModel: ErrorDemoViewModel = koinViewModel(),
+) {
+    val state by viewModel.state.collectAsStateWithLifecycle()
+
+    ObserveAsEvents(viewModel.events) { event ->
+        when (event) {
+            ErrorDemoEvent.NavigateBack -> onNavigateBack()
+        }
+    }
+
+    ErrorDemoScreen(state = state, onAction = viewModel::onAction)
+}
+
+/** Pure, stateless screen — previewable without a ViewModel. */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun ErrorDemoScreen(
+    state: ErrorDemoState,
+    onAction: (ErrorDemoAction) -> Unit,
+) {
+    AppScaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text(stringResource(R.string.error_demo_title)) },
+                navigationIcon = {
+                    IconButton(onClick = { onAction(ErrorDemoAction.OnBackClick) }) {
+                        Icon(
+                            imageVector = Icons.AutoMirrored.Filled.ArrowBack,
+                            contentDescription = stringResource(R.string.cd_back),
+                        )
+                    }
+                },
+            )
+        },
+    ) { innerPadding ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(innerPadding)
+                .padding(16.dp),
+            verticalArrangement = Arrangement.spacedBy(12.dp),
+        ) {
+            Text(
+                text = stringResource(R.string.error_demo_intro),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+
+            OutlinedButton(
+                onClick = { onAction(ErrorDemoAction.OnForceError(ErrorScenario.NO_INTERNET)) },
+                modifier = Modifier.fillMaxWidth(),
+            ) { Text(stringResource(R.string.error_demo_force_no_internet)) }
+            OutlinedButton(
+                onClick = { onAction(ErrorDemoAction.OnForceError(ErrorScenario.NOT_FOUND)) },
+                modifier = Modifier.fillMaxWidth(),
+            ) { Text(stringResource(R.string.error_demo_force_not_found)) }
+            OutlinedButton(
+                onClick = { onAction(ErrorDemoAction.OnForceError(ErrorScenario.SERVER_ERROR)) },
+                modifier = Modifier.fillMaxWidth(),
+            ) { Text(stringResource(R.string.error_demo_force_server)) }
+            Button(
+                onClick = { onAction(ErrorDemoAction.OnLoadSuccess) },
+                modifier = Modifier.fillMaxWidth(),
+            ) { Text(stringResource(R.string.error_demo_load_success)) }
+
+            // Result area: loading → mapped error (with retry) → success → idle hint.
+            Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                val error = state.error
+                when {
+                    state.isLoading -> LoadingIndicator()
+                    error != null -> ErrorState(
+                        message = error.asString(),
+                        onRetry = { onAction(ErrorDemoAction.OnRetry) },
+                    )
+                    state.loaded -> Text(
+                        text = stringResource(R.string.error_demo_success),
+                        style = MaterialTheme.typography.titleMedium,
+                    )
+                    else -> Text(
+                        text = stringResource(R.string.error_demo_hint),
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        textAlign = TextAlign.Center,
+                    )
+                }
+            }
+        }
+    }
+}
+
+@Preview
+@Composable
+private fun ErrorDemoScreenIdlePreview() {
+    AppTheme { ErrorDemoScreen(state = ErrorDemoState(), onAction = {}) }
+}
+
+@Preview
+@Composable
+private fun ErrorDemoScreenErrorPreview() {
+    AppTheme {
+        ErrorDemoScreen(
+            state = ErrorDemoState(
+                error = com.example.architecture.core.presentation.UiText.DynamicString(
+                    "No internet connection. Check your network and try again.",
+                ),
+            ),
+            onAction = {},
+        )
+    }
+}
--- a/feature/characters/presentation-compose/src/main/res/values/strings.xml
+++ b/feature/characters/presentation-compose/src/main/res/values/strings.xml
@@ -10,6 +10,17 @@
    <string name="cd_more_options">More options</string>
    <string name="menu_about">About</string>
    <string name="menu_open_as_views">Open as Views</string>
+    <string name="menu_error_demo">Error handling demo</string>
+
+    <!-- Error-handling demo screen -->
+    <string name="error_demo_title">Error handling demo</string>
+    <string name="error_demo_intro">Force a network failure to watch it flow through the pipeline: DataError.Network → toUiText() → the shared ErrorState. Retry re-issues the same request; a successful load clears the error.</string>
+    <string name="error_demo_force_no_internet">Force: No internet</string>
+    <string name="error_demo_force_not_found">Force: Not found</string>
+    <string name="error_demo_force_server">Force: Server error</string>
+    <string name="error_demo_load_success">Load (success)</string>
+    <string name="error_demo_success">Loaded successfully ✓</string>
+    <string name="error_demo_hint">Pick an action above to see the result here.</string>

    <!-- Detail screen -->
    <string name="character_detail_title">Character</string>