Got at least one data fetching method working; turns out, we can't use a patched LogicStack to get the data

Vendor/EmbedIO-3.5.2/HttpContextExtensions-Requests.cs

@@ -0,0 +1,175 @@
+using System;
+using System.Collections.Specialized;
+using System.IO;
+using System.Threading.Tasks;
+using EmbedIO.Utilities;
+using Swan;
+
+namespace EmbedIO
+{
+    partial class HttpContextExtensions
+    {
+        private static readonly object FormDataKey = new object();
+        private static readonly object QueryDataKey = new object();
+
+        /// <summary>
+        /// Asynchronously retrieves the request body as an array of <see langword="byte"/>s.
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>A <see cref="Task{TResult}">Task</see>, representing the ongoing operation,
+        /// whose result will be an array of <see cref="byte"/>s containing the request body.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        public static async Task<byte[]> GetRequestBodyAsByteArrayAsync(this IHttpContext @this)
+        {
+            using var buffer = new MemoryStream();
+            using var stream = @this.OpenRequestStream();
+            await stream.CopyToAsync(buffer, WebServer.StreamCopyBufferSize, @this.CancellationToken).ConfigureAwait(false);
+            return buffer.ToArray();
+        }
+
+        /// <summary>
+        /// Asynchronously buffers the request body into a read-only <see cref="MemoryStream"/>.
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>A <see cref="Task{TResult}">Task</see>, representing the ongoing operation,
+        /// whose result will be a read-only <see cref="MemoryStream"/> containing the request body.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        public static async Task<MemoryStream> GetRequestBodyAsMemoryStreamAsync(this IHttpContext @this)
+            => new MemoryStream(
+                await GetRequestBodyAsByteArrayAsync(@this).ConfigureAwait(false),
+                false);
+
+        /// <summary>
+        /// Asynchronously retrieves the request body as a string.
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>A <see cref="Task{TResult}">Task</see>, representing the ongoing operation,
+        /// whose result will be a <see langword="string"/> representation of the request body.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        public static async Task<string> GetRequestBodyAsStringAsync(this IHttpContext @this)
+        {
+            using var reader = @this.OpenRequestText();
+            return await reader.ReadToEndAsync().ConfigureAwait(false);
+        }
+
+        /// <summary>
+        /// <para>Asynchronously deserializes a request body, using the default request deserializer.</para>
+        /// <para>As of EmbedIO version 3.0, the default response serializer has the same behavior of JSON
+        /// request parsing methods of version 2.</para>
+        /// </summary>
+        /// <typeparam name="TData">The expected type of the deserialized data.</typeparam>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>A <see cref="Task{TResult}">Task</see>, representing the ongoing operation,
+        /// whose result will be the deserialized data.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        public static Task<TData> GetRequestDataAsync<TData>(this IHttpContext @this)
+            => RequestDeserializer.Default<TData>(@this);
+
+        /// <summary>
+        /// Asynchronously deserializes a request body, using the specified request deserializer.
+        /// </summary>
+        /// <typeparam name="TData">The expected type of the deserialized data.</typeparam>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <param name="deserializer">A <see cref="RequestDeserializerCallback{TData}"/> used to deserialize the request body.</param>
+        /// <returns>A <see cref="Task{TResult}">Task</see>, representing the ongoing operation,
+        /// whose result will be the deserialized data.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="deserializer"/> is <see langword="null"/>.</exception>
+        public static Task<TData> GetRequestDataAsync<TData>(this IHttpContext @this,RequestDeserializerCallback<TData> deserializer)
+            => Validate.NotNull(nameof(deserializer), deserializer)(@this);
+
+        /// <summary>
+        /// Asynchronously parses a request body in <c>application/x-www-form-urlencoded</c> format.
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>A <see cref="Task{TResult}">Task</see>, representing the ongoing operation,
+        /// whose result will be a read-only <see cref="NameValueCollection"/>of form field names and values.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        /// <remarks>
+        /// <para>This method may safely be called more than once for the same <see cref="IHttpContext"/>:
+        /// it will return the same collection instead of trying to parse the request body again.</para>
+        /// </remarks>
+        public static async Task<NameValueCollection> GetRequestFormDataAsync(this IHttpContext @this)
+        {
+            if (!@this.Items.TryGetValue(FormDataKey, out var previousResult))
+            {
+                NameValueCollection result;
+                try
+                {
+                    using var reader = @this.OpenRequestText();
+                    result = UrlEncodedDataParser.Parse(await reader.ReadToEndAsync().ConfigureAwait(false), false);
+                }
+                catch (Exception e)
+                {
+                    @this.Items[FormDataKey] = e;
+                    throw;
+                }
+
+                @this.Items[FormDataKey] = result;
+                return result;
+            }
+
+            switch (previousResult)
+            {
+                case NameValueCollection collection:
+                    return collection;
+
+                case Exception exception:
+                    throw exception.RethrowPreservingStackTrace();
+
+                case null:
+                    throw SelfCheck.Failure($"Previous result of {nameof(HttpContextExtensions)}.{nameof(GetRequestFormDataAsync)} is null.");
+
+                default:
+                    throw SelfCheck.Failure($"Previous result of {nameof(HttpContextExtensions)}.{nameof(GetRequestFormDataAsync)} is of unexpected type {previousResult.GetType().FullName}");
+            }
+        }
+
+        /// <summary>
+        /// Parses a request URL query. Note that this is different from getting the <see cref="IHttpRequest.QueryString"/> property,
+        /// in that fields without an equal sign are treated as if they have an empty value, instead of their keys being grouped
+        /// as values of the <c>null</c> key.
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>A read-only <see cref="NameValueCollection"/>.</returns>
+        /// <exception cref="NullReferenceException"><paramref name="this"/> is <see langword="null"/>.</exception>
+        /// <remarks>
+        /// <para>This method may safely be called more than once for the same <see cref="IHttpContext"/>:
+        /// it will return the same collection instead of trying to parse the request body again.</para>
+        /// </remarks>
+        public static NameValueCollection GetRequestQueryData(this IHttpContext @this)
+        {
+            if (!@this.Items.TryGetValue(QueryDataKey, out var previousResult))
+            {
+                NameValueCollection result;
+                try
+                {
+                    result = UrlEncodedDataParser.Parse(@this.Request.Url.Query, false);
+                }
+                catch (Exception e)
+                {
+                    @this.Items[FormDataKey] = e;
+                    throw;
+                }
+
+                @this.Items[FormDataKey] = result;
+                return result;
+            }
+
+            switch (previousResult)
+            {
+                case NameValueCollection collection:
+                    return collection;
+
+                case Exception exception:
+                    throw exception.RethrowPreservingStackTrace();
+
+                case null:
+                    throw SelfCheck.Failure($"Previous result of {nameof(HttpContextExtensions)}.{nameof(GetRequestQueryData)} is null.");
+
+                default:
+                    throw SelfCheck.Failure($"Previous result of {nameof(HttpContextExtensions)}.{nameof(GetRequestQueryData)} is of unexpected type {previousResult.GetType().FullName}");
+            }
+        }
+    }
+}