refactor: Improve data validation, allow deletion of invalid snapshots (#279)

* feat: move validation to be on unpack

* refactor: add validation and handling for invalid data to UX

* fix: `runAfter` not firing on unpack failure

* locales: minor update to `data_list_item_invalid`

common/src/main/java/net/william278/husksync/command/ItemsCommand.java

@@ -71,26 +71,43 @@ public abstract class ItemsCommand extends Command implements TabProvider {
     private void showLatestItems(@NotNull OnlineUser viewer, @NotNull User user) {
         plugin.getRedisManager().getUserData(user.getUuid(), user).thenAccept(data -> data
                 .or(() -> plugin.getDatabase().getLatestSnapshot(user))
-                .ifPresentOrElse(
-                        snapshot -> this.showItems(
-                                viewer, snapshot.unpack(plugin), user,
-                                viewer.hasPermission(getPermission("edit"))
-                        ),
-                        () -> plugin.getLocales().getLocale("error_no_data_to_display")
-                                .ifPresent(viewer::sendMessage)
-                ));
+                .or(() -> {
+                    plugin.getLocales().getLocale("error_no_data_to_display")
+                            .ifPresent(viewer::sendMessage);
+                    return Optional.empty();
+                })
+                .flatMap(packed -> {
+                    if (packed.isInvalid()) {
+                        plugin.getLocales().getLocale("error_invalid_data", packed.getInvalidReason(plugin))
+                                .ifPresent(viewer::sendMessage);
+                        return Optional.empty();
+                    }
+                    return Optional.of(packed.unpack(plugin));
+                })
+                .ifPresent(snapshot -> this.showItems(
+                        viewer, snapshot, user, viewer.hasPermission(getPermission("edit"))
+                )));
     }
 
     // View a specific version of the user data
     private void showSnapshotItems(@NotNull OnlineUser viewer, @NotNull User user, @NotNull UUID version) {
         plugin.getDatabase().getSnapshot(user, version)
-                .ifPresentOrElse(
-                        snapshot -> this.showItems(
-                                viewer, snapshot.unpack(plugin), user, false
-                        ),
-                        () -> plugin.getLocales().getLocale("error_invalid_version_uuid")
-                                .ifPresent(viewer::sendMessage)
-                );
+                .or(() -> {
+                    plugin.getLocales().getLocale("error_invalid_version_uuid")
+                            .ifPresent(viewer::sendMessage);
+                    return Optional.empty();
+                })
+                .flatMap(packed -> {
+                    if (packed.isInvalid()) {
+                        plugin.getLocales().getLocale("error_invalid_data", packed.getInvalidReason(plugin))
+                                .ifPresent(viewer::sendMessage);
+                        return Optional.empty();
+                    }
+                    return Optional.of(packed.unpack(plugin));
+                })
+                .ifPresent(snapshot -> this.showItems(
+                        viewer, snapshot, user, false
+                ));
     }
 
     // Show a GUI menu with the correct item data from the snapshot

common/src/main/java/net/william278/husksync/command/UserDataCommand.java

@@ -61,7 +61,7 @@ public class UserDataCommand extends Command implements TabProvider {
                 .or(() -> parseStringArg(args, 0).flatMap(name -> plugin.getDatabase().getUserByName(name)))
                 .or(() -> args.length < 2 && executor instanceof User userExecutor
                         ? Optional.of(userExecutor) : Optional.empty());
-        final Optional<UUID> optionalUuid = parseUUIDArg(args, 2).or(() -> parseUUIDArg(args, 1));
+        final Optional<UUID> uuid = parseUUIDArg(args, 2).or(() -> parseUUIDArg(args, 1));
         if (optionalUser.isEmpty()) {
             plugin.getLocales().getLocale("error_invalid_player")
                     .ifPresent(executor::sendMessage);
@@ -70,164 +70,179 @@ public class UserDataCommand extends Command implements TabProvider {
 
         final User user = optionalUser.get();
         switch (subCommand) {
-            case "view" -> optionalUuid.ifPresentOrElse(
-                    // Show the specified snapshot
-                    version -> plugin.getDatabase().getSnapshot(user, version).ifPresentOrElse(
-                            data -> DataSnapshotOverview.of(
-                                    data.unpack(plugin), data.getFileSize(plugin), user, plugin
-                            ).show(executor),
-                            () -> plugin.getLocales().getLocale("error_invalid_version_uuid")
-                                    .ifPresent(executor::sendMessage)),
-
-                    // Show the latest snapshot
-                    () -> plugin.getDatabase().getLatestSnapshot(user).ifPresentOrElse(
-                            data -> DataSnapshotOverview.of(
-                                    data.unpack(plugin), data.getFileSize(plugin), user, plugin
-                            ).show(executor),
-                            () -> plugin.getLocales().getLocale("error_no_data_to_display")
-                                    .ifPresent(executor::sendMessage))
+            case "view" -> uuid.ifPresentOrElse(
+                    version -> viewSnapshot(executor, user, version),
+                    () -> viewLatestSnapshot(executor, user)
             );
-
-            case "list" -> {
-                // Check if there is data to display
-                final List<DataSnapshot.Packed> dataList = plugin.getDatabase().getAllSnapshots(user);
-                if (dataList.isEmpty()) {
-                    plugin.getLocales().getLocale("error_no_data_to_display")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Show the list to the player
-                DataSnapshotList.create(dataList, user, plugin).displayPage(
-                        executor,
-                        parseIntArg(args, 2).or(() -> parseIntArg(args, 1)).orElse(1)
-                );
-            }
-
-            case "delete" -> {
-                if (optionalUuid.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_syntax",
+            case "list" -> listSnapshots(
+                    executor, user, parseIntArg(args, 2).or(() -> parseIntArg(args, 1)).orElse(1)
+            );
+            case "delete" -> uuid.ifPresentOrElse(
+                    version -> deleteSnapshot(executor, user, version),
+                    () -> plugin.getLocales().getLocale("error_invalid_syntax",
                                     "/userdata delete <username> <version_uuid>")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Delete user data by specified UUID and clear their data cache
-                final UUID version = optionalUuid.get();
-                if (!plugin.getDatabase().deleteSnapshot(user, version)) {
-                    plugin.getLocales().getLocale("error_invalid_version_uuid")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-                plugin.getRedisManager().clearUserData(user);
-
-                plugin.getLocales().getLocale("data_deleted",
-                                version.toString().split("-")[0],
-                                version.toString(),
-                                user.getUsername(),
-                                user.getUuid().toString())
-                        .ifPresent(executor::sendMessage);
-            }
-
-            case "restore" -> {
-                if (optionalUuid.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_syntax",
+                            .ifPresent(executor::sendMessage)
+            );
+            case "restore" -> uuid.ifPresentOrElse(
+                    version -> restoreSnapshot(executor, user, version),
+                    () -> plugin.getLocales().getLocale("error_invalid_syntax",
                                     "/userdata restore <username> <version_uuid>")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Restore user data by specified UUID
-                final Optional<DataSnapshot.Packed> optionalData = plugin.getDatabase().getSnapshot(user, optionalUuid.get());
-                if (optionalData.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_version_uuid")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Restore users with a minimum of one health (prevent restoring players with <=0 health)
-                final DataSnapshot.Packed data = optionalData.get().copy();
-                data.edit(plugin, (unpacked -> {
-                    unpacked.getHealth().ifPresent(status -> status.setHealth(Math.max(1, status.getHealth())));
-                    unpacked.setSaveCause(DataSnapshot.SaveCause.BACKUP_RESTORE);
-                    unpacked.setPinned(
-                            plugin.getSettings().getSynchronization().doAutoPin(DataSnapshot.SaveCause.BACKUP_RESTORE)
-                    );
-                }));
-
-                // Save data
-                final RedisManager redis = plugin.getRedisManager();
-                plugin.getDataSyncer().saveData(user, data, (u, s) -> {
-                    redis.getUserData(u).ifPresent(d -> redis.setUserData(u, s, RedisKeyType.TTL_1_YEAR));
-                    redis.sendUserDataUpdate(u, s);
-                    plugin.getLocales().getLocale("data_restored", u.getUsername(), u.getUuid().toString(),
-                            s.getShortId(), s.getId().toString()).ifPresent(executor::sendMessage);
-                });
-            }
-
-            case "pin" -> {
-                if (optionalUuid.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_syntax",
+                            .ifPresent(executor::sendMessage)
+            );
+            case "pin" -> uuid.ifPresentOrElse(
+                    version -> pinSnapshot(executor, user, version),
+                    () -> plugin.getLocales().getLocale("error_invalid_syntax",
                                     "/userdata pin <username> <version_uuid>")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Check that the data exists
-                final Optional<DataSnapshot.Packed> optionalData = plugin.getDatabase().getSnapshot(user, optionalUuid.get());
-                if (optionalData.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_version_uuid")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Pin or unpin the data
-                final DataSnapshot.Packed data = optionalData.get();
-                if (data.isPinned()) {
-                    plugin.getDatabase().unpinSnapshot(user, data.getId());
-                } else {
-                    plugin.getDatabase().pinSnapshot(user, data.getId());
-                }
-                plugin.getLocales().getLocale(data.isPinned() ? "data_unpinned" : "data_pinned", data.getShortId(),
-                                data.getId().toString(), user.getUsername(), user.getUuid().toString())
-                        .ifPresent(executor::sendMessage);
-            }
-
-            case "dump" -> {
-                if (optionalUuid.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_syntax",
-                                    "/userdata dump <username> <version_uuid>")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Determine dump type
-                final boolean webDump = parseStringArg(args, 3)
-                        .map(arg -> arg.equalsIgnoreCase("web"))
-                        .orElse(false);
-                final Optional<DataSnapshot.Packed> data = plugin.getDatabase().getSnapshot(user, optionalUuid.get());
-                if (data.isEmpty()) {
-                    plugin.getLocales().getLocale("error_invalid_version_uuid")
-                            .ifPresent(executor::sendMessage);
-                    return;
-                }
-
-                // Dump the data
-                final DataSnapshot.Packed userData = data.get();
-                final DataDumper dumper = DataDumper.create(userData, user, plugin);
-                try {
-                    plugin.getLocales().getLocale("data_dumped", userData.getShortId(), user.getUsername(),
-                            (webDump ? dumper.toWeb() : dumper.toFile())).ifPresent(executor::sendMessage);
-                } catch (Throwable e) {
-                    plugin.log(Level.SEVERE, "Failed to dump user data", e);
-                }
-            }
-
+                            .ifPresent(executor::sendMessage)
+            );
+            case "dump" -> uuid.ifPresentOrElse(
+                    version -> dumpSnapshot(executor, user, version, parseStringArg(args, 3)
+                            .map(arg -> arg.equalsIgnoreCase("web")).orElse(false)),
+                    () -> plugin.getLocales().getLocale("error_invalid_syntax",
+                                    "/userdata dump <web/file> <username> <version_uuid>")
+                            .ifPresent(executor::sendMessage)
+            );
             default -> plugin.getLocales().getLocale("error_invalid_syntax", getUsage())
                     .ifPresent(executor::sendMessage);
         }
     }
 
+    // Show the latest snapshot
+    private void viewLatestSnapshot(@NotNull CommandUser executor, @NotNull User user) {
+        plugin.getDatabase().getLatestSnapshot(user).ifPresentOrElse(
+                data -> {
+                    if (data.isInvalid()) {
+                        plugin.getLocales().getLocale("error_invalid_data", data.getInvalidReason(plugin))
+                                .ifPresent(executor::sendMessage);
+                        return;
+                    }
+                    DataSnapshotOverview.of(data.unpack(plugin), data.getFileSize(plugin), user, plugin)
+                            .show(executor);
+                },
+                () -> plugin.getLocales().getLocale("error_no_data_to_display")
+                        .ifPresent(executor::sendMessage)
+        );
+    }
+
+    // Show the specified snapshot
+    private void viewSnapshot(@NotNull CommandUser executor, @NotNull User user, @NotNull UUID version) {
+        plugin.getDatabase().getSnapshot(user, version).ifPresentOrElse(
+                data -> {
+                    if (data.isInvalid()) {
+                        plugin.getLocales().getLocale("error_invalid_data", data.getInvalidReason(plugin))
+                                .ifPresent(executor::sendMessage);
+                        return;
+                    }
+                    DataSnapshotOverview.of(data.unpack(plugin), data.getFileSize(plugin), user, plugin)
+                            .show(executor);
+                },
+                () -> plugin.getLocales().getLocale("error_invalid_version_uuid")
+                        .ifPresent(executor::sendMessage)
+        );
+    }
+
+    // View a list of snapshots
+    private void listSnapshots(@NotNull CommandUser executor, @NotNull User user, int page) {
+        final List<DataSnapshot.Packed> dataList = plugin.getDatabase().getAllSnapshots(user);
+        if (dataList.isEmpty()) {
+            plugin.getLocales().getLocale("error_no_data_to_display")
+                    .ifPresent(executor::sendMessage);
+            return;
+        }
+        DataSnapshotList.create(dataList, user, plugin).displayPage(executor, page);
+    }
+
+    // Delete a snapshot
+    private void deleteSnapshot(@NotNull CommandUser executor, @NotNull User user, @NotNull UUID version) {
+        if (!plugin.getDatabase().deleteSnapshot(user, version)) {
+            plugin.getLocales().getLocale("error_invalid_version_uuid")
+                    .ifPresent(executor::sendMessage);
+            return;
+        }
+        plugin.getRedisManager().clearUserData(user);
+        plugin.getLocales().getLocale("data_deleted",
+                        version.toString().split("-")[0],
+                        version.toString(),
+                        user.getUsername(),
+                        user.getUuid().toString())
+                .ifPresent(executor::sendMessage);
+    }
+
+    // Restore a snapshot
+    private void restoreSnapshot(@NotNull CommandUser executor, @NotNull User user, @NotNull UUID version) {
+        final Optional<DataSnapshot.Packed> optionalData = plugin.getDatabase().getSnapshot(user, version);
+        if (optionalData.isEmpty()) {
+            plugin.getLocales().getLocale("error_invalid_version_uuid")
+                    .ifPresent(executor::sendMessage);
+            return;
+        }
+
+        // Restore users with a minimum of one health (prevent restoring players with <= 0 health)
+        final DataSnapshot.Packed data = optionalData.get().copy();
+        if (data.isInvalid()) {
+            plugin.getLocales().getLocale("error_invalid_data", data.getInvalidReason(plugin))
+                    .ifPresent(executor::sendMessage);
+            return;
+        }
+        data.edit(plugin, (unpacked -> {
+            unpacked.getHealth().ifPresent(status -> status.setHealth(Math.max(1, status.getHealth())));
+            unpacked.setSaveCause(DataSnapshot.SaveCause.BACKUP_RESTORE);
+            unpacked.setPinned(
+                    plugin.getSettings().getSynchronization().doAutoPin(DataSnapshot.SaveCause.BACKUP_RESTORE)
+            );
+        }));
+
+        // Save data
+        final RedisManager redis = plugin.getRedisManager();
+        plugin.getDataSyncer().saveData(user, data, (u, s) -> {
+            redis.getUserData(u).ifPresent(d -> redis.setUserData(u, s, RedisKeyType.TTL_1_YEAR));
+            redis.sendUserDataUpdate(u, s);
+            plugin.getLocales().getLocale("data_restored", u.getUsername(), u.getUuid().toString(),
+                    s.getShortId(), s.getId().toString()).ifPresent(executor::sendMessage);
+        });
+    }
+
+    // Pin a snapshot
+    private void pinSnapshot(@NotNull CommandUser executor, @NotNull User user, @NotNull UUID version) {
+        final Optional<DataSnapshot.Packed> optionalData = plugin.getDatabase().getSnapshot(user, version);
+        if (optionalData.isEmpty()) {
+            plugin.getLocales().getLocale("error_invalid_version_uuid")
+                    .ifPresent(executor::sendMessage);
+            return;
+        }
+
+        // Pin or unpin the data
+        final DataSnapshot.Packed data = optionalData.get();
+        if (data.isPinned()) {
+            plugin.getDatabase().unpinSnapshot(user, data.getId());
+        } else {
+            plugin.getDatabase().pinSnapshot(user, data.getId());
+        }
+        plugin.getLocales().getLocale(data.isPinned() ? "data_unpinned" : "data_pinned", data.getShortId(),
+                        data.getId().toString(), user.getUsername(), user.getUuid().toString())
+                .ifPresent(executor::sendMessage);
+    }
+
+    // Dump a snapshot
+    private void dumpSnapshot(@NotNull CommandUser executor, @NotNull User user, @NotNull UUID version, boolean webDump) {
+        final Optional<DataSnapshot.Packed> data = plugin.getDatabase().getSnapshot(user, version);
+        if (data.isEmpty()) {
+            plugin.getLocales().getLocale("error_invalid_version_uuid")
+                    .ifPresent(executor::sendMessage);
+            return;
+        }
+
+        // Dump the data
+        final DataSnapshot.Packed userData = data.get();
+        final DataDumper dumper = DataDumper.create(userData, user, plugin);
+        try {
+            plugin.getLocales().getLocale("data_dumped", userData.getShortId(), user.getUsername(),
+                    (webDump ? dumper.toWeb() : dumper.toFile())).ifPresent(executor::sendMessage);
+        } catch (Throwable e) {
+            plugin.log(Level.SEVERE, "Failed to dump user data", e);
+        }
+    }
+
     @Nullable
     @Override
     public List<String> suggest(@NotNull CommandUser executor, @NotNull String[] args) {

common/src/main/java/net/william278/husksync/data/DataException.java

@@ -0,0 +1,72 @@
+/*
+ * This file is part of HuskSync, licensed under the Apache License 2.0.
+ *
+ *  Copyright (c) William278 <will27528@gmail.com>
+ *  Copyright (c) contributors
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package net.william278.husksync.data;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import net.william278.husksync.HuskSync;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.function.BiFunction;
+
+/**
+ * An exception related to {@link DataSnapshot} formatting, thrown if an exception occurs when unpacking a snapshot
+ */
+@Getter
+public class DataException extends IllegalStateException {
+
+    private final Reason reason;
+
+    private DataException(@NotNull DataException.Reason reason, @NotNull DataSnapshot data, @NotNull HuskSync plugin) {
+        super(reason.getMessage(plugin, data));
+        this.reason = reason;
+    }
+
+    /**
+     * Reasons why {@link DataException}s were thrown
+     */
+    @AllArgsConstructor
+    public enum Reason {
+        INVALID_MINECRAFT_VERSION((plugin, snapshot) -> String.format("The Minecraft version of the snapshot (%s) is " +
+                        "newer than the server's version (%s). Ensure each server is on the same version of Minecraft.",
+                snapshot.getMinecraftVersion(), plugin.getMinecraftVersion())),
+        INVALID_FORMAT_VERSION((plugin, snapshot) -> String.format("The format version of the snapshot (%s) is newer " +
+                        "than the server's version (%s). Ensure each server is running the same version of HuskSync.",
+                snapshot.getFormatVersion(), DataSnapshot.CURRENT_FORMAT_VERSION)),
+        INVALID_PLATFORM_TYPE((plugin, snapshot) -> String.format("The platform type of the snapshot (%s) does " +
+                        "not match the server's platform type (%s). Ensure each server has the same platform type.",
+                snapshot.getPlatformType(), plugin.getPlatformType())),
+        NO_LEGACY_CONVERTER((plugin, snapshot) -> String.format("No legacy converter to convert format version: %s",
+                snapshot.getFormatVersion()));
+
+        private final BiFunction<HuskSync, DataSnapshot, String> exception;
+
+        @NotNull
+        String getMessage(@NotNull HuskSync plugin, @NotNull DataSnapshot data) {
+            return exception.apply(plugin, data);
+        }
+
+        @NotNull
+        DataException toException(@NotNull DataSnapshot data, @NotNull HuskSync plugin) {
+            return new DataException(this, data, plugin);
+        }
+    }
+
+}

common/src/main/java/net/william278/husksync/data/DataSnapshot.java

@@ -84,6 +84,11 @@ public class DataSnapshot {
     @SerializedName("data")
     protected Map<String, String> data;
 
+    // If the snapshot is invalid, this will be set to the validation exception
+    @Nullable
+    @Expose(serialize = false, deserialize = false)
+    transient DataException.Reason exception = null;
+
     private DataSnapshot(@NotNull UUID id, boolean pinned, @NotNull OffsetDateTime timestamp,
                          @NotNull String saveCause, @NotNull String serverName, @NotNull Map<String, String> data,
                          @NotNull Version minecraftVersion, @NotNull String platformType, int formatVersion) {
@@ -108,37 +113,25 @@ public class DataSnapshot {
     @NotNull
     @ApiStatus.Internal
     public static DataSnapshot.Packed deserialize(@NotNull HuskSync plugin, byte[] data, @Nullable UUID id,
-                                                  @Nullable OffsetDateTime timestamp) throws IllegalStateException {
+                                                  @Nullable OffsetDateTime timestamp) {
         final DataSnapshot.Packed snapshot = plugin.getDataAdapter().fromBytes(data, DataSnapshot.Packed.class);
         if (snapshot.getMinecraftVersion().compareTo(plugin.getMinecraftVersion()) > 0) {
-            throw new IllegalStateException(String.format("Cannot deserialize data because the Minecraft version of " +
-                            "the data snapshot (%s) is newer than the server's Minecraft version (%s)." +
-                            "Please ensure each server is running the same version of Minecraft.",
-                    snapshot.getMinecraftVersion(), plugin.getMinecraftVersion()));
+            return snapshot.invalid(DataException.Reason.INVALID_MINECRAFT_VERSION);
         }
         if (snapshot.getFormatVersion() > CURRENT_FORMAT_VERSION) {
-            throw new IllegalStateException(String.format("Cannot deserialize data because the format version of " +
-                            "the data snapshot (%s) is newer than the current format version (%s). " +
-                            "Please ensure each server is running the latest version of HuskSync.",
-                    snapshot.getFormatVersion(), CURRENT_FORMAT_VERSION));
+            return snapshot.invalid(DataException.Reason.INVALID_FORMAT_VERSION);
         }
         if (snapshot.getFormatVersion() < 4) {
             if (plugin.getLegacyConverter().isPresent()) {
                 return plugin.getLegacyConverter().get().convert(
-                        data,
-                        Objects.requireNonNull(id, "Attempted legacy conversion with null UUID!"),
+                        data, Objects.requireNonNull(id, "Attempted legacy conversion with null UUID!"),
                         Objects.requireNonNull(timestamp, "Attempted legacy conversion with null timestamp!")
                 );
             }
-            throw new IllegalStateException(String.format(
-                    "No legacy converter to convert format version: %s", snapshot.getFormatVersion()
-            ));
+            return snapshot.invalid(DataException.Reason.NO_LEGACY_CONVERTER);
         }
         if (!snapshot.getPlatformType().equalsIgnoreCase(plugin.getPlatformType())) {
-            throw new IllegalStateException(String.format("Cannot deserialize data because the platform type of " +
-                            "the data snapshot (%s) is different to the server platform type (%s). " +
-                            "Please ensure each server is running the same platform type.",
-                    snapshot.getPlatformType(), plugin.getPlatformType()));
+            return snapshot.invalid(DataException.Reason.INVALID_PLATFORM_TYPE);
         }
         return snapshot;
     }
@@ -163,6 +156,7 @@ public class DataSnapshot {
 
     /**
      * <b>Internal use only</b> Set the ID of the snapshot
+     *
      * @param id The snapshot ID
      * @since 3.0
      */
@@ -293,6 +287,32 @@ public class DataSnapshot {
             super(id, pinned, timestamp, saveCause, serverName, data, minecraftVersion, platformType, formatVersion);
         }
 
+        @NotNull
+        @ApiStatus.Internal
+        DataSnapshot.Packed invalid(@NotNull DataException.Reason reason) {
+            this.exception = reason;
+            return this;
+        }
+
+        public boolean isInvalid() {
+            return exception != null;
+        }
+
+        @NotNull
+        public String getInvalidReason(@NotNull HuskSync plugin) {
+            if (exception == null) {
+                throw new IllegalStateException("Attempted to get an invalid reason for a valid snapshot!");
+            }
+            return exception.getMessage(plugin, this);
+        }
+
+        @ApiStatus.Internal
+        void validate(@NotNull HuskSync plugin) throws DataException {
+            if (exception != null) {
+                throw exception.toException(this, plugin);
+            }
+        }
+
         @ApiStatus.Internal
         public void edit(@NotNull HuskSync plugin, @NotNull Consumer<Unpacked> editor) {
             final Unpacked data = unpack(plugin);
@@ -332,7 +352,8 @@ public class DataSnapshot {
         }
 
         @NotNull
-        public DataSnapshot.Unpacked unpack(@NotNull HuskSync plugin) {
+        public DataSnapshot.Unpacked unpack(@NotNull HuskSync plugin) throws DataException {
+            this.validate(plugin);
             return new Unpacked(
                     id, pinned, timestamp, saveCause, serverName, data,
                     getMinecraftVersion(), platformType, formatVersion, plugin
@@ -905,7 +926,8 @@ public class DataSnapshot {
 
         /**
          * Get or create a {@link SaveCause} from a name and whether it should fire a save event
-         * @param name the name to be displayed
+         *
+         * @param name           the name to be displayed
          * @param firesSaveEvent whether the cause should fire a save event
          * @return the cause
          */

common/src/main/java/net/william278/husksync/data/UserDataHolder.java

@@ -97,6 +97,7 @@ public interface UserDataHolder extends DataHolder {
             unpacked = snapshot.unpack(plugin);
         } catch (Throwable e) {
             plugin.log(Level.SEVERE, String.format("Failed to unpack data snapshot for %s", getUsername()), e);
+            runAfter.accept(false);
             return;
         }
 

common/src/main/java/net/william278/husksync/util/DataSnapshotList.java

@@ -47,7 +47,7 @@ public class DataSnapshotList {
         final AtomicInteger snapshotNumber = new AtomicInteger(1);
         this.paginatedList = PaginatedList.of(snapshots.stream()
                         .map(snapshot -> plugin.getLocales()
-                                .getRawLocale("data_list_item",
+                                .getRawLocale(!snapshot.isInvalid() ? "data_list_item" : "data_list_item_invalid",
                                         getNumberIcon(snapshotNumber.getAndIncrement()),
                                         dataOwner.getUsername(),
                                         snapshot.getId().toString(),
@@ -58,7 +58,8 @@ public class DataSnapshotList {
                                         snapshot.getTimestamp().format(DateTimeFormatter
                                                 .ofLocalizedDateTime(FormatStyle.LONG, FormatStyle.MEDIUM)),
                                         snapshot.getSaveCause().getLocale(plugin),
-                                        String.format("%.2fKiB", snapshot.getFileSize(plugin) / 1024f))
+                                        String.format("%.2fKiB", snapshot.getFileSize(plugin) / 1024f),
+                                        snapshot.isInvalid() ? snapshot.getInvalidReason(plugin) : "")
                                 .orElse("• " + snapshot.getId())).toList(),
                 plugin.getLocales().getBaseChatList(6)
                         .setHeaderFormat(plugin.getLocales()