Merge 3eff5faa2c into 5bbb706b3c

DiscordChatExporter.Cli/Commands/Base/ExportCommandBase.cs

@@ -179,6 +179,7 @@ public abstract class ExportCommandBase : DiscordCommandBase
         // Export
         var cancellationToken = console.RegisterCancellationHandler();
         var errorsByChannel = new ConcurrentDictionary<Channel, string>();
+        var warningsByChannel = new ConcurrentDictionary<Channel, string>();
 
         await console.Output.WriteLineAsync($"Exporting {channels.Count} channel(s)...");
         await console
@@ -236,6 +237,9 @@ public abstract class ExportCommandBase : DiscordCommandBase
                                 }
                             );
                         }
+                        catch (ChannelNotExportedException ex) {
+                            warningsByChannel[channel] = ex.Message;
+                        }
                         catch (DiscordChatExporterException ex) when (!ex.IsFatal)
                         {
                             errorsByChannel[channel] = ex.Message;
@@ -252,26 +256,33 @@ public abstract class ExportCommandBase : DiscordCommandBase
             );
         }
 
-        // Print errors
-        if (errorsByChannel.Any())
+        // Print errors and warnings
+        if (errorsByChannel.Any() || warningsByChannel.Any())
         {
-            await console.Output.WriteLineAsync();
-
-            using (console.WithForegroundColor(ConsoleColor.Red))
+            var tuples = new List<(ConcurrentDictionary<Channel, string>, ConsoleColor, string)>
             {
-                await console.Error.WriteLineAsync(
-                    $"Failed to export {errorsByChannel.Count} the following channel(s):"
-                );
-            }
+                (errorsByChannel,   ConsoleColor.Red,    "Failed to export the following channels:"),
+                (warningsByChannel, ConsoleColor.Yellow, "No messages exported for the following channels:")
+            };
 
-            foreach (var (channel, error) in errorsByChannel)
-            {
-                await console.Error.WriteAsync($"{channel.GetHierarchicalName()}: ");
-                using (console.WithForegroundColor(ConsoleColor.Red))
-                    await console.Error.WriteLineAsync(error);
-            }
+            foreach (var (messages, color, title) in tuples) {
+                if (! messages.Any())
+                    continue;
 
-            await console.Error.WriteLineAsync();
+                await console.Output.WriteLineAsync();
+
+                using (console.WithForegroundColor(color))
+                    await console.Error.WriteLineAsync(title);
+
+                foreach (var (channel, message) in messages)
+                {
+                    await console.Error.WriteAsync($"{channel.GetHierarchicalName()}: ");
+                    using (console.WithForegroundColor(color))
+                        await console.Error.WriteLineAsync(message);
+                }
+
+                await console.Error.WriteLineAsync();
+            }
         }
 
         // Fail the command only if ALL channels failed to export.

DiscordChatExporter.Core/Exceptions/ChannelNotExportedException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace DiscordChatExporter.Core.Exceptions;
+
+// Thrown when there is circumstancially no message to export with given parameters,
+// though it should not be treated as a runtime error; simply warn instead
+public class ChannelNotExportedException(string message)
+: DiscordChatExporterException(message, false, null) {
+}

DiscordChatExporter.Core/Exporting/ChannelExporter.cs

@@ -27,45 +27,35 @@ public class ChannelExporter(DiscordClient discord)
             );
         }
 
+        // Build context
+        var context = new ExportContext(discord, request);
+        await context.PopulateChannelsAndRolesAsync(cancellationToken);
+
+        // Export messages
+        await using var messageExporter = new MessageExporter(context);
+        await messageExporter.EnsureFileIsCreated(cancellationToken);
+
         // Check if the channel is empty
         if (request.Channel.IsEmpty)
         {
-            throw new DiscordChatExporterException(
-                $"Channel '{request.Channel.Name}' "
-                    + $"of guild '{request.Guild.Name}' "
-                    + $"does not contain any messages."
-            );
-        }
-
-        // Check if the 'after' boundary is valid
-        if (request.After is not null && !request.Channel.MayHaveMessagesAfter(request.After.Value))
-        {
-            throw new DiscordChatExporterException(
+            throw new ChannelNotExportedException(
                 $"Channel '{request.Channel.Name}' "
                     + $"of guild '{request.Guild.Name}' "
-                    + $"does not contain any messages within the specified period."
+                    + $"does not contain any messages; an empty file will be created."
             );
         }
 
-        // Check if the 'before' boundary is valid
-        if (
-            request.Before is not null
-            && !request.Channel.MayHaveMessagesBefore(request.Before.Value)
-        )
+        // Check if the 'before' and 'after' boundaries are valid
+        if ((request.Before is not null && !request.Channel.MayHaveMessagesBefore(request.Before.Value)) ||
+             (request.After is not null && !request.Channel.MayHaveMessagesAfter(request.After.Value)))
         {
-            throw new DiscordChatExporterException(
+            throw new ChannelNotExportedException(
                 $"Channel '{request.Channel.Name}' "
                     + $"of guild '{request.Guild.Name}' "
-                    + $"does not contain any messages within the specified period."
+                    + $"does not contain any messages within the specified period; an empty file will be created."
             );
         }
 
-        // Build context
-        var context = new ExportContext(discord, request);
-        await context.PopulateChannelsAndRolesAsync(cancellationToken);
-
-        // Export messages
-        await using var messageExporter = new MessageExporter(context);
         await foreach (
             var message in discord.GetMessagesAsync(
                 request.Channel.Id,
@@ -98,15 +88,5 @@ public class ChannelExporter(DiscordClient discord)
                 );
             }
         }
-
-        // Throw if no messages were exported
-        if (messageExporter.MessagesExported <= 0)
-        {
-            throw new DiscordChatExporterException(
-                $"Channel '{request.Channel.Name}' (#{request.Channel.Id}) "
-                    + $"of guild '{request.Guild.Name}' (#{request.Guild.Id}) "
-                    + $"does not contain any matching messages within the specified period."
-            );
-        }
     }
 }

DiscordChatExporter.Core/Exporting/MessageExporter.cs

@@ -30,6 +30,11 @@ internal partial class MessageExporter(ExportContext context) : IAsyncDisposable
         }
     }
 
+    // Unless explicitly called, file will be created before writing first message
+    public async ValueTask EnsureFileIsCreated(CancellationToken cancellationToken = default) {
+        await GetWriterAsync(cancellationToken);
+    }
+
     private async ValueTask<MessageWriter> GetWriterAsync(
         CancellationToken cancellationToken = default
     )

DiscordChatExporter.Gui/ViewModels/Components/DashboardViewModel.cs

@@ -283,6 +283,12 @@ public partial class DashboardViewModel : ViewModelBase
 
                         Interlocked.Increment(ref successfulExportCount);
                     }
+                    catch (ChannelNotExportedException ex) {
+                        _snackbarManager.Notify(ex.Message.TrimEnd('.'));
+
+                        // FIXME: not exactly successful, but not a failure either. Not ideal to duplicate the line
+                        Interlocked.Increment(ref successfulExportCount);
+                    }
                     catch (DiscordChatExporterException ex) when (!ex.IsFatal)
                     {
                         _snackbarManager.Notify(ex.Message.TrimEnd('.'));