fix: Surface all exceptions to the user instead of crashing (#565)

Previous code would handle some expected exceptions (IO, HTTP) when
fetching a timeline, and show them to the user. Any other exception
would crash.

Now, surface all exceptions. Treat IO and HTTP exceptions as retryable
and show the "Retry" option, all others are considered non-retryable.

Provide a specific error string for exceptions caused by bad JSON.

app/src/main/java/app/pachli/components/account/media/AccountMediaRemoteMediator.kt

@@ -20,7 +20,6 @@ import androidx.paging.ExperimentalPagingApi
 import androidx.paging.LoadType
 import androidx.paging.PagingState
 import androidx.paging.RemoteMediator
-import app.pachli.components.timeline.util.ifExpected
 import app.pachli.core.database.model.AccountEntity
 import app.pachli.core.navigation.AttachmentViewData
 import app.pachli.core.network.retrofit.MastodonApi
@@ -72,9 +71,7 @@ class AccountMediaRemoteMediator(
             viewModel.currentSource?.invalidate()
             return MediatorResult.Success(endOfPaginationReached = statuses.isEmpty())
         } catch (e: Exception) {
-            return ifExpected(e) {
+            return MediatorResult.Error(e)
-                MediatorResult.Error(e)
-            }
         }
     }
 }

app/src/main/java/app/pachli/components/notifications/NotificationsViewModel.kt

@@ -32,7 +32,6 @@ import app.pachli.appstore.MuteConversationEvent
 import app.pachli.appstore.MuteEvent
 import app.pachli.components.timeline.FilterKind
 import app.pachli.components.timeline.FiltersRepository
-import app.pachli.components.timeline.util.ifExpected
 import app.pachli.core.accounts.AccountManager
 import app.pachli.core.network.model.Filter
 import app.pachli.core.network.model.FilterContext
@@ -409,7 +408,7 @@ class NotificationsViewModel @Inject constructor(
                             }
                         }
                     } catch (e: Exception) {
-                        ifExpected(e) { _uiErrorChannel.send(UiError.make(e, it)) }
+                        _uiErrorChannel.send(UiError.make(e, it))
                     }
                 }
         }
@@ -428,7 +427,7 @@ class NotificationsViewModel @Inject constructor(
                         }
                         uiSuccess.emit(NotificationActionSuccess.from(action))
                     } catch (e: Exception) {
-                        ifExpected(e) { _uiErrorChannel.send(UiError.make(e, action)) }
+                        _uiErrorChannel.send(UiError.make(e, action))
                     }
                 }
         }

app/src/main/java/app/pachli/components/timeline/TimelineFragment.kt

@@ -41,6 +41,7 @@ import androidx.recyclerview.widget.SimpleItemAnimator
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout.OnRefreshListener
 import app.pachli.R
 import app.pachli.adapter.StatusBaseViewHolder
+import app.pachli.components.timeline.util.isExpected
 import app.pachli.components.timeline.viewmodel.CachedTimelineViewModel
 import app.pachli.components.timeline.viewmodel.InfallibleUiAction
 import app.pachli.components.timeline.viewmodel.NetworkTimelineViewModel
@@ -431,20 +432,32 @@ class TimelineFragment :
                                     // Show errors as a snackbar if there is existing content to show
                                     // (either cached, or in the adapter), or as a full screen error
                                     // otherwise.
+                                    //
+                                    // Expected errors can be retried, unexpected ones cannot
                                     if (adapter.itemCount > 0) {
                                         snackbar = Snackbar.make(
                                             (activity as ActionButtonActivity).actionButton
                                                 ?: binding.root,
                                             message,
                                             Snackbar.LENGTH_INDEFINITE,
-                                        )
+                                        ).apply {
-                                            .setAction(app.pachli.core.ui.R.string.action_retry) { adapter.retry() }
+                                            if (error.isExpected()) {
+                                                setAction(app.pachli.core.ui.R.string.action_retry) { adapter.retry() }
+                                            }
+                                        }
+
                                         snackbar!!.show()
                                     } else {
-                                        binding.statusView.setup(error) {
+                                        val callback: ((v: View) -> Unit)? = if (error.isExpected()) {
+                                            {
                                                 snackbar?.dismiss()
                                                 adapter.retry()
                                             }
+                                        } else {
+                                            null
+                                        }
+
+                                        binding.statusView.setup(error, callback)
                                         binding.statusView.show()
                                         binding.recyclerView.hide()
                                     }

app/src/main/java/app/pachli/components/timeline/viewmodel/CachedTimelineRemoteMediator.kt

@@ -37,7 +37,6 @@ import app.pachli.core.network.model.Links
 import app.pachli.core.network.model.Status
 import app.pachli.core.network.retrofit.MastodonApi
 import com.squareup.moshi.Moshi
-import java.io.IOException
 import kotlinx.coroutines.async
 import kotlinx.coroutines.coroutineScope
 import okhttp3.Headers
@@ -78,6 +77,7 @@ class CachedTimelineRemoteMediator(
                     Timber.d("Loading from item: %s", statusId)
                     getInitialPage(statusId, state.config.pageSize)
                 }
+
                 LoadType.APPEND -> {
                     val rke = remoteKeyDao.remoteKeyForKind(
                         activeAccount.id,
@@ -87,6 +87,7 @@ class CachedTimelineRemoteMediator(
                     Timber.d("Loading from remoteKey: %s", rke)
                     api.homeTimeline(maxId = rke.key, limit = state.config.pageSize)
                 }
+
                 LoadType.PREPEND -> {
                     val rke = remoteKeyDao.remoteKeyForKind(
                         activeAccount.id,
@@ -168,9 +169,8 @@ class CachedTimelineRemoteMediator(
             }
 
             return MediatorResult.Success(endOfPaginationReached = false)
-        } catch (e: IOException) {
+        } catch (e: Exception) {
-            MediatorResult.Error(e)
+            Timber.e(e, "Error loading, LoadType = %s", loadType)
-        } catch (e: HttpException) {
             MediatorResult.Error(e)
         }
     }

app/src/main/java/app/pachli/components/timeline/viewmodel/NetworkTimelineRemoteMediator.kt

@@ -126,9 +126,8 @@ class NetworkTimelineRemoteMediator(
             }
 
             return MediatorResult.Success(endOfPaginationReached = endOfPaginationReached)
-        } catch (e: IOException) {
+        } catch (e: Exception) {
-            MediatorResult.Error(e)
+            Timber.e(e, "Error loading, LoadType = %s", loadType)
-        } catch (e: HttpException) {
             MediatorResult.Error(e)
         }
     }

app/src/main/java/app/pachli/components/timeline/viewmodel/TimelineViewModel.kt

@@ -43,7 +43,6 @@ import app.pachli.appstore.StatusEditedEvent
 import app.pachli.appstore.UnfollowEvent
 import app.pachli.components.timeline.FilterKind
 import app.pachli.components.timeline.FiltersRepository
-import app.pachli.components.timeline.util.ifExpected
 import app.pachli.core.accounts.AccountManager
 import app.pachli.core.network.model.Filter
 import app.pachli.core.network.model.FilterContext
@@ -361,7 +360,7 @@ abstract class TimelineViewModel(
                         }.getOrThrow()
                         uiSuccess.emit(StatusActionSuccess.from(action))
                     } catch (e: Exception) {
-                        ifExpected(e) { _uiErrorChannel.send(UiError.make(e, action)) }
+                        _uiErrorChannel.send(UiError.make(e, action))
                     }
                 }
         }

core/ui/build.gradle.kts

@@ -38,6 +38,9 @@ dependencies {
     // Uses HttpException from Retrofit
     implementation(projects.core.network)
 
+    // Uses JsonDataException from Moshi
+    implementation(libs.moshi)
+
     // Some views inherit from AndroidX views
     implementation(libs.bundles.androidx)
 

core/ui/src/main/kotlin/app/pachli/core/ui/extensions/ThrowableExtensions.kt

@@ -20,6 +20,7 @@ package app.pachli.core.ui.extensions
 import android.content.Context
 import app.pachli.core.network.extensions.getServerErrorMessage
 import app.pachli.core.ui.R
+import com.squareup.moshi.JsonDataException
 import java.io.IOException
 import retrofit2.HttpException
 
@@ -40,5 +41,6 @@ fun Throwable.getDrawableRes(): Int = when (this) {
 fun Throwable.getErrorString(context: Context): String = getServerErrorMessage() ?: when (this) {
     is IOException -> context.getString(R.string.error_network_fmt, this.message)
     is HttpException -> if (this.code() == 404) context.getString(R.string.error_404_not_found_fmt, this.message) else context.getString(R.string.error_generic_fmt, this.message)
+    is JsonDataException -> context.getString(R.string.error_json_data_fmt, this.message)
     else -> context.getString(R.string.error_generic_fmt, this.message)
 }

core/ui/src/main/res/values/strings.xml

@@ -4,6 +4,7 @@
     <string name="error_network_fmt">A network error occurred: %s</string>
     <string name="error_generic_fmt">An error occurred: %s</string>
     <string name="error_404_not_found_fmt">Your server does not support this feature: %1$s</string>
+    <string name="error_json_data_fmt">Your server returned an invalid response: %1$s</string>
     <string name="error_generic">An error occurred.</string>
     <string name="message_empty">Nothing here.</string>
     <string name="action_retry">Retry</string>