[CLI] Display channel name for errors during ExportMultipleAsync (#452)

DiscordChatExporter.Cli/Commands/Base/ExportMultipleCommandBase.cs

@@ -32,7 +32,7 @@ namespace DiscordChatExporter.Cli.Commands.Base
             var operations = progress.Wrap().CreateOperations(channels.Count);
 
             var successfulExportCount = 0;
-            var errors = new ConcurrentBag<string>();
+            var errors = new ConcurrentBag<(Channel, string)>();
 
             await channels.Zip(operations).ParallelForEachAsync(async tuple =>
             {
@@ -61,7 +61,7 @@ namespace DiscordChatExporter.Cli.Commands.Base
                 }
                 catch (DiscordChatExporterException ex) when (!ex.IsCritical)
                 {
-                    errors.Add(ex.Message);
+                    errors.Add((channel, ex.Message));
                 }
                 finally
                 {
@@ -71,8 +71,8 @@ namespace DiscordChatExporter.Cli.Commands.Base
 
             console.Output.WriteLine();
 
-            foreach (var error in errors)
-                console.Error.WriteLine(error);
+            foreach (var (channel, error) in errors)
+                console.Error.WriteLine($"Channel '{channel}': {error}");
 
             console.Output.WriteLine($"Successfully exported {successfulExportCount} channel(s).");
         }

DiscordChatExporter.Domain/Exceptions/DiscordChatExporterException.cs

@@ -46,9 +46,9 @@ Failed to perform an HTTP request.
             return new DiscordChatExporterException(message);
         }
 
-        internal static DiscordChatExporterException ChannelIsEmpty(string channel)
+        internal static DiscordChatExporterException ChannelIsEmpty()
         {
-            var message = $"Channel '{channel}' contains no messages for the specified period.";
+            var message = $"No messages for the specified period.";
             return new DiscordChatExporterException(message);
         }
     }

DiscordChatExporter.Domain/Exporting/ChannelExporter.cs

@@ -59,7 +59,7 @@ namespace DiscordChatExporter.Domain.Exporting
 
             // Throw if no messages were exported
             if (!exportedAnything)
-                throw DiscordChatExporterException.ChannelIsEmpty(request.Channel.Name);
+                throw DiscordChatExporterException.ChannelIsEmpty();
         }
     }
 }