[Fix] Don't dispose streams in DefaultRestClient (#2652)

* Duplicate file streams before sending

* Other code needs to dispose their objects

* Another resource to dispose

* Stop disposing and copying streams in SendAsync

* Fix inverted boolean check

Co-authored-by: Dmitry <dimson-n@users.noreply.github.com>

* Await results for using statement to work

---------

Co-authored-by: Dmitry <dimson-n@users.noreply.github.com>

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -1068,11 +1068,11 @@ namespace Discord.Rest
         /// <returns>
         ///     A task that represents the asynchronous creation operation. The task result contains the created sticker.
         /// </returns>
-        public Task<CustomSticker> CreateStickerAsync(string name,  string path, IEnumerable<string> tags, string description = null,
+        public async Task<CustomSticker> CreateStickerAsync(string name,  string path, IEnumerable<string> tags, string description = null,
             RequestOptions options = null)
         {
-            var fs = File.OpenRead(path);
+            using var fs = File.OpenRead(path);
-            return CreateStickerAsync(name, fs, Path.GetFileName(fs.Name), tags,  description,options);
+            return await CreateStickerAsync(name, fs, Path.GetFileName(fs.Name), tags,  description,options);
         }
         /// <summary>
         ///     Creates a new sticker in this guild

src/Discord.Net.Rest/Entities/Interactions/Modals/RestModal.cs

@@ -228,6 +228,7 @@ namespace Discord.Rest
             fileName ??= Path.GetFileName(filePath);
             Preconditions.NotNullOrEmpty(fileName, nameof(fileName), "File Name must not be empty or null");
 
+            using var fileStream = !string.IsNullOrEmpty(filePath) ? new MemoryStream(File.ReadAllBytes(filePath), false) : null;
             var args = new API.Rest.CreateWebhookMessageParams
             {
                 Content = text,
@@ -235,7 +236,7 @@ namespace Discord.Rest
                 IsTTS = isTTS,
                 Embeds = embeds.Select(x => x.ToModel()).ToArray(),
                 Components = component?.Components.Select(x => new API.ActionRowComponent(x)).ToArray() ?? Optional<API.ActionRowComponent[]>.Unspecified,
-                File = !string.IsNullOrEmpty(filePath) ? new MultipartFile(new MemoryStream(File.ReadAllBytes(filePath), false), fileName) : Optional<MultipartFile>.Unspecified
+                File = fileStream != null ? new MultipartFile(fileStream, fileName) : Optional<MultipartFile>.Unspecified
             };
 
             if (ephemeral)

src/Discord.Net.Rest/Net/DefaultRestClient.cs

@@ -1,7 +1,7 @@
-using Discord.Net.Converters;
 using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -101,62 +101,68 @@ namespace Discord.Net.Rest
             IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null)
         {
             string uri = Path.Combine(_baseUrl, endpoint);
-            using (var restRequest = new HttpRequestMessage(GetMethod(method), uri))
+
-            {
+            // HttpRequestMessage implements IDisposable but we do not need to dispose it as it merely disposes of its Content property,
-                if (reason != null)
+            // which we can do as needed. And regarding that, we do not want to take responsibility for disposing of content provided by
-                    restRequest.Headers.Add("X-Audit-Log-Reason", Uri.EscapeDataString(reason));
+            // the caller of this function, since it's possible that the caller wants to reuse it or is forced to reuse it because of a
-                if (requestHeaders != null)
+            // 429 response. Therefore, by convention, we only dispose the content objects created in this function (if any).
-                    foreach (var header in requestHeaders)
+            //
-                        restRequest.Headers.Add(header.Key, header.Value);
+            // See this comment explaining why this is safe: https://github.com/aspnet/Security/issues/886#issuecomment-229181249
-                var content = new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture));
+            // See also the source for HttpRequestMessage: https://github.com/microsoft/referencesource/blob/master/System/net/System/Net/Http/HttpRequestMessage.cs
-                MemoryStream memoryStream = null;
-                if (multipartParams != null)
-                {
-                    foreach (var p in multipartParams)
-                    {
-                        switch (p.Value)
-                        {
 #pragma warning disable IDISP004
-                            case string stringValue:
+            var restRequest = new HttpRequestMessage(GetMethod(method), uri);
-                                { content.Add(new StringContent(stringValue, Encoding.UTF8, "text/plain"), p.Key); continue; }
-                            case byte[] byteArrayValue:
-                                { content.Add(new ByteArrayContent(byteArrayValue), p.Key); continue; }
-                            case Stream streamValue:
-                                { content.Add(new StreamContent(streamValue), p.Key); continue; }
-                            case MultipartFile fileValue:
-                                {
-                                    var stream = fileValue.Stream;
-                                    if (!stream.CanSeek)
-                                    {
-                                        memoryStream = new MemoryStream();
-                                        await stream.CopyToAsync(memoryStream).ConfigureAwait(false);
-                                        memoryStream.Position = 0;
-#pragma warning disable IDISP001
-                                        stream = memoryStream;
-#pragma warning restore IDISP001
-                                    }
-
-                                    var streamContent = new StreamContent(stream);
-                                    var extension = fileValue.Filename.Split('.').Last();
-
-                                    if (fileValue.ContentType != null)
-                                        streamContent.Headers.ContentType = new MediaTypeHeaderValue(fileValue.ContentType);
-
-                                    content.Add(streamContent, p.Key, fileValue.Filename);
 #pragma warning restore IDISP004
 
-                                    continue;
+            if (reason != null)
-                                }
+                restRequest.Headers.Add("X-Audit-Log-Reason", Uri.EscapeDataString(reason));
-                            default:
+            if (requestHeaders != null)
-                                throw new InvalidOperationException($"Unsupported param type \"{p.Value.GetType().Name}\".");
+                foreach (var header in requestHeaders)
-                        }
+                    restRequest.Headers.Add(header.Key, header.Value);
-                    }
+            var content = new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture));
+
+            static StreamContent GetStreamContent(Stream stream)
+            {
+                if (stream.CanSeek)
+                {
+                    // Reset back to the beginning; it may have been used elsewhere or in a previous request.
+                    stream.Position = 0;
                 }
-                restRequest.Content = content;
+
-                var result = await SendInternalAsync(restRequest, cancelToken, headerOnly).ConfigureAwait(false);
+#pragma warning disable IDISP004
-                memoryStream?.Dispose();
+                return new StreamContent(stream);
-                return result;
+#pragma warning restore IDISP004
             }
+
+            foreach (var p in multipartParams ?? ImmutableDictionary<string, object>.Empty)
+            {
+                switch (p.Value)
+                {
+#pragma warning disable IDISP004
+                    case string stringValue:
+                        { content.Add(new StringContent(stringValue, Encoding.UTF8, "text/plain"), p.Key); continue; }
+                    case byte[] byteArrayValue:
+                        { content.Add(new ByteArrayContent(byteArrayValue), p.Key); continue; }
+                    case Stream streamValue:
+                        { content.Add(GetStreamContent(streamValue), p.Key); continue; }
+                    case MultipartFile fileValue:
+                        {
+                            var streamContent = GetStreamContent(fileValue.Stream);
+
+                            if (fileValue.ContentType != null)
+                                streamContent.Headers.ContentType = new MediaTypeHeaderValue(fileValue.ContentType);
+
+                            content.Add(streamContent, p.Key, fileValue.Filename);
+#pragma warning restore IDISP004
+
+                            continue;
+                        }
+                    default:
+                        throw new InvalidOperationException($"Unsupported param type \"{p.Value.GetType().Name}\".");
+                }
+            }
+
+            restRequest.Content = content;
+            return await SendInternalAsync(restRequest, cancelToken, headerOnly).ConfigureAwait(false);
         }
 
         private async Task<RestResponse> SendInternalAsync(HttpRequestMessage request, CancellationToken cancelToken, bool headerOnly)

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -1558,11 +1558,11 @@ namespace Discord.WebSocket
         /// <returns>
         ///     A task that represents the asynchronous creation operation. The task result contains the created sticker.
         /// </returns>
-        public Task<SocketCustomSticker> CreateStickerAsync(string name,  string path, IEnumerable<string> tags, string description = null,
+        public async Task<SocketCustomSticker> CreateStickerAsync(string name,  string path, IEnumerable<string> tags, string description = null,
             RequestOptions options = null)
         {
-            var fs = File.OpenRead(path);
+            using var fs = File.OpenRead(path);
-            return CreateStickerAsync(name,  fs, Path.GetFileName(fs.Name), tags, description, options);
+            return await CreateStickerAsync(name,  fs, Path.GetFileName(fs.Name), tags, description, options);
         }
         /// <summary>
         ///     Creates a new sticker in this guild