#452 exclude Content-Type header by default for multipart AddString

and related refactoring of CapturedStringContent constructors

Test/Flurl.Test/Http/MultipartTests.cs

@@ -17,29 +17,33 @@ public class MultipartTests
 		public void can_build_multipart_content() {
 			var content = new CapturedMultipartContent()
 				.AddString("string", "foo")
+				.AddString("string2", "bar", "text/blah")
 				.AddStringParts(new { part1 = 1, part2 = 2, part3 = (string)null }) // part3 should be excluded
 				.AddFile("file1", Path.Combine("path", "to", "image1.jpg"), "image/jpeg")
 				.AddFile("file2", Path.Combine("path", "to", "image2.jpg"), "image/jpeg", fileName: "new-name.jpg")
 				.AddJson("json", new { foo = "bar" })
 				.AddUrlEncoded("urlEnc", new { fizz = "buzz" });
 
-			Assert.AreEqual(7, content.Parts.Length);
-
-			AssertStringPart<CapturedStringContent>(content.Parts[0], "string", "foo");
-			AssertStringPart<CapturedStringContent>(content.Parts[1], "part1", "1");
-			AssertStringPart<CapturedStringContent>(content.Parts[2], "part2", "2");
-			AssertFilePart(content.Parts[3], "file1", "image1.jpg", "image/jpeg");
-			AssertFilePart(content.Parts[4], "file2", "new-name.jpg", "image/jpeg");
-			AssertStringPart<CapturedJsonContent>(content.Parts[5], "json", "{\"foo\":\"bar\"}");
-			AssertStringPart<CapturedUrlEncodedContent>(content.Parts[6], "urlEnc", "fizz=buzz");
+			Assert.AreEqual(8, content.Parts.Length);
+			AssertStringPart<CapturedStringContent>(content.Parts[0], "string", "foo", null);
+			AssertStringPart<CapturedStringContent>(content.Parts[1], "string2", "bar", "text/blah");
+			AssertStringPart<CapturedStringContent>(content.Parts[2], "part1", "1", null);
+			AssertStringPart<CapturedStringContent>(content.Parts[3], "part2", "2", null);
+			AssertFilePart(content.Parts[4], "file1", "image1.jpg", "image/jpeg");
+			AssertFilePart(content.Parts[5], "file2", "new-name.jpg", "image/jpeg");
+			AssertStringPart<CapturedJsonContent>(content.Parts[6], "json", "{\"foo\":\"bar\"}", "application/json; charset=UTF-8");
+			AssertStringPart<CapturedUrlEncodedContent>(content.Parts[7], "urlEnc", "fizz=buzz", "application/x-www-form-urlencoded");
 		}
 
-		private void AssertStringPart<TContent>(HttpContent part, string name, string content) {
+		private void AssertStringPart<TContent>(HttpContent part, string name, string content, string contentType) {
 			Assert.IsInstanceOf<TContent>(part);
 		    Assert.AreEqual(name, part.Headers.ContentDisposition.Name);
 		    Assert.AreEqual(content, (part as CapturedStringContent)?.Content);
-		    Assert.IsFalse(part.Headers.Contains("Content-Type")); // #392
-	    }
+		    if (contentType == null)
+			    Assert.IsFalse(part.Headers.Contains("Content-Type")); // #392
+		    else
+			    Assert.AreEqual(contentType, part.Headers.GetValues("Content-Type").SingleOrDefault());
+		}
 
 	    private void AssertFilePart(HttpContent part, string name, string fileName, string contentType) {
 		    Assert.IsInstanceOf<FileContent>(part);

src/Flurl.Http/Content/CapturedJsonContent.cs

@@ -12,6 +12,6 @@ public class CapturedJsonContent : CapturedStringContent
 		/// Initializes a new instance of the <see cref="CapturedJsonContent"/> class.
 		/// </summary>
 		/// <param name="json">The json.</param>
-		public CapturedJsonContent(string json) : base(json, Encoding.UTF8, "application/json") { }
+		public CapturedJsonContent(string json) : base(json, "application/json; charset=UTF-8") { }
 	}
 }

src/Flurl.Http/Content/CapturedMultipartContent.cs

@@ -35,31 +35,29 @@ public CapturedMultipartContent(FlurlHttpSettings settings = null) : base("form-
 		/// <param name="name">The control name of the part.</param>
 		/// <param name="content">The HttpContent of the part.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
-		public CapturedMultipartContent Add(string name, HttpContent content) => AddInternal(name, content, true, null);
+		public CapturedMultipartContent Add(string name, HttpContent content) => AddInternal(name, content, null);
 
 		/// <summary>
 		/// Add a simple string part to the multipart request.
 		/// </summary>
-		/// <param name="name">The control name of the part.</param>
-		/// <param name="content">The string content of the part.</param>
-		/// <param name="encoding">The encoding of the part.</param>
-		/// <param name="mediaType">The media type of the part.</param>
+		/// <param name="name">The name of the part.</param>
+		/// <param name="value">The string value of the part.</param>
+		/// <param name="contentType">The value of the Content-Type header for this part. If null (the default), header will be excluded, which complies with the HTML 5 standard.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
-		public CapturedMultipartContent AddString(string name, string content, Encoding encoding = null, string mediaType = null) =>
-			AddInternal(name, new CapturedStringContent(content, encoding, mediaType), false, null);
+		public CapturedMultipartContent AddString(string name, string value, string contentType = null) =>
+			AddInternal(name, new CapturedStringContent(value, contentType), null);
 
 		/// <summary>
 		/// Add multiple string parts to the multipart request by parsing an object's properties into control name/content pairs.
 		/// </summary>
 		/// <param name="data">The object (typically anonymous) whose properties are parsed into control name/content pairs.</param>
-		/// <param name="encoding">The encoding of the parts.</param>
-		/// <param name="mediaType">The media type of the parts.</param>
+		/// <param name="contentType">The value of the Content-Type header for this part. If null, header will be excluded, which complies with the HTML 5 standard.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
-		public CapturedMultipartContent AddStringParts(object data, Encoding encoding = null, string mediaType = null) {
+		public CapturedMultipartContent AddStringParts(object data, string contentType = null) {
 			foreach (var kv in data.ToKeyValuePairs()) {
 				if (kv.Value == null)
 					continue;
-				AddString(kv.Key, kv.Value.ToInvariantString(), encoding, mediaType);
+				AddString(kv.Key, kv.Value.ToInvariantString(), contentType);
 			}
 			return this;
 		}
@@ -71,7 +69,7 @@ public CapturedMultipartContent AddStringParts(object data, Encoding encoding =
 		/// <param name="data">The content of the part, which will be serialized to JSON.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
 		public CapturedMultipartContent AddJson(string name, object data) =>
-			AddInternal(name, new CapturedJsonContent(_settings.JsonSerializer.Serialize(data)), false, null);
+			AddInternal(name, new CapturedJsonContent(_settings.JsonSerializer.Serialize(data)), null);
 
 		/// <summary>
 		/// Add a URL-encoded part to the multipart request.
@@ -80,50 +78,45 @@ public CapturedMultipartContent AddJson(string name, object data) =>
 		/// <param name="data">The content of the part, whose properties will be parsed and serialized to URL-encoded format.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
 		public CapturedMultipartContent AddUrlEncoded(string name, object data) =>
-			AddInternal(name, new CapturedUrlEncodedContent(_settings.UrlEncodedSerializer.Serialize(data)), false, null);
+			AddInternal(name, new CapturedUrlEncodedContent(_settings.UrlEncodedSerializer.Serialize(data)), null);
 
 		/// <summary>
 		/// Adds a file to the multipart request from a stream.
 		/// </summary>
 		/// <param name="name">The control name of the part.</param>
 		/// <param name="stream">The file stream to send.</param>
 		/// <param name="fileName">The filename, added to the Content-Disposition header of the part.</param>
-		/// <param name="mediaType">The media type of the file.</param>
+		/// <param name="contentType">The content type of the file.</param>
 		/// <param name="bufferSize">The buffer size of the stream upload in bytes. Defaults to 4096.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
-		public CapturedMultipartContent AddFile(string name, Stream stream, string fileName, string mediaType = null, int bufferSize = 4096) {
+		public CapturedMultipartContent AddFile(string name, Stream stream, string fileName, string contentType = null, int bufferSize = 4096) {
 			var content = new StreamContent(stream, bufferSize);
-			if (mediaType != null)
-				content.Headers.ContentType = new MediaTypeHeaderValue(mediaType);
-			return AddInternal(name, content, true, fileName);
+			if (contentType != null)
+				content.Headers.TryAddWithoutValidation("Content-Type", contentType);
+			return AddInternal(name, content, fileName);
 		}
 
 		/// <summary>
 		/// Adds a file to the multipart request from a local path.
 		/// </summary>
 		/// <param name="name">The control name of the part.</param>
 		/// <param name="path">The local path to the file.</param>
-		/// <param name="mediaType">The media type of the file.</param>
+		/// <param name="contentType">The content type of the file.</param>
 		/// <param name="bufferSize">The buffer size of the stream upload in bytes. Defaults to 4096.</param>
 		/// <param name="fileName">The filename, added to the Content-Disposition header of the part. Defaults to local file name.</param>
 		/// <returns>This CapturedMultipartContent instance (supports method chaining).</returns>
-		public CapturedMultipartContent AddFile(string name, string path, string mediaType = null, int bufferSize = 4096, string fileName = null) {
+		public CapturedMultipartContent AddFile(string name, string path, string contentType = null, int bufferSize = 4096, string fileName = null) {
 			fileName = fileName ?? FileUtil.GetFileName(path);
 			var content = new FileContent(path, bufferSize);
-			if (mediaType != null)
-				content.Headers.ContentType = new MediaTypeHeaderValue(mediaType);
-			return AddInternal(name, content, true, fileName);
+			if (contentType != null)
+				content.Headers.TryAddWithoutValidation("Content-Type", contentType);
+			return AddInternal(name, content, fileName);
 		}
 
-		private CapturedMultipartContent AddInternal(string name, HttpContent content, bool allowContentType, string fileName) {
+		private CapturedMultipartContent AddInternal(string name, HttpContent content, string fileName) {
 			if (string.IsNullOrWhiteSpace(name))
 				throw new ArgumentException("name must not be empty", nameof(name));
 
-			// StringContent is the simplest way to add a string part, but it always
-			// includes Content-Type, and per HTML spec that's not allowed (#392)
-			if (!allowContentType && content.Headers.Contains("Content-Type"))
-				content.Headers.Remove("Content-Type");
-
 			content.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data") {
 				Name = name,
 				FileName = fileName,

src/Flurl.Http/Content/CapturedStringContent.cs

@@ -1,4 +1,5 @@
 using System.Net.Http;
+using System.Net.Http.Headers;
 using System.Text;
 
 namespace Flurl.Http.Content
@@ -14,16 +15,24 @@ public class CapturedStringContent : StringContent
 		/// </summary>
 		public string Content { get; }
 
+		/// <summary>
+		/// Initializes a new instance of <see cref="CapturedStringContent"/> with a Content-Type header of text/plain; charset=UTF-8
+		/// </summary>
+		/// <param name="content">The content.</param>
+		public CapturedStringContent(string content) : base(content) {
+			Content = content;
+		}
+
 		/// <summary>
 		/// Initializes a new instance of the <see cref="CapturedStringContent"/> class.
 		/// </summary>
 		/// <param name="content">The content.</param>
-		/// <param name="encoding">The encoding.</param>
-		/// <param name="mediaType">Type of the media.</param>
-		public CapturedStringContent(string content, Encoding encoding = null, string mediaType = null) : 
-			base(content, encoding, mediaType) 
-		{
+		/// <param name="contentType">Value of the Content-Type header. To exclude the header, set to null explicitly.</param>
+		public CapturedStringContent(string content, string contentType) : base(content) {
 			Content = content;
+			Headers.Remove("Content-Type");
+			if (contentType != null)
+				Headers.TryAddWithoutValidation("Content-Type", contentType);
 		}
 	}
 }

src/Flurl.Http/Content/CapturedUrlEncodedContent.cs

@@ -11,6 +11,6 @@ public class CapturedUrlEncodedContent : CapturedStringContent
 		/// Initializes a new instance of the <see cref="CapturedUrlEncodedContent"/> class.
 		/// </summary>
 		/// <param name="data">Content represented as a (typically anonymous) object, which will be parsed into name/value pairs.</param>
-		public CapturedUrlEncodedContent(string data) : base(data, null, "application/x-www-form-urlencoded") { }
+		public CapturedUrlEncodedContent(string data) : base(data, "application/x-www-form-urlencoded") { }
 	}
 }

src/Flurl.Http/HttpMessageExtensions.cs

@@ -91,7 +91,6 @@ private static void SetHeader(this HttpMessage msg, string name, object value, b
 			}
 		}
 
-
 		/// <summary>
 		/// Wrapper class for treating HttpRequestMessage and HttpResponseMessage uniformly. (Unfortunately they don't have a common interface.)
 		/// </summary>