Fix mime type assignment issues in FileModel

The MimeType property was not properly set in some cases, such as when
creating a new file, or when saving a file with a new name and extension.

FileModel now ensures that the MimeType property is always up to date,
and TextBufferFileModel now updates the content type of the buffer
when creating a new document or when saving a document.

Fixes VSTS# 825629 - No error message shows up in TypeScript files

5 files changed, 71 insertions, 15 deletions

diff --git a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/DocumentModel.cs b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/DocumentModel.cs
index 18e0b74522..e05ed9f1c2 100644
--- a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/DocumentModel.cs
+++ b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/DocumentModel.cs
@@ -103,14 +103,20 @@ namespace MonoDevelop.Ide.Gui.Documents
 
 		public void CreateNew ()
 		{
+			InitializeNew ();
+			ModelRepresentation.CreateNew ();
+		}
+
+		protected void InitializeNew ()
+		{
 			if (IsLoaded)
 				throw new InvalidOperationException ("Model already loaded");
 			if (Data.IsLinked)
 				throw new InvalidOperationException ("Model already linked");
 			isNew = true;
-			ModelRepresentation.CreateNew ();
 		}
 
+
 		public bool IsNew {
 			get {
 				CheckInitialized ();
diff --git a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileDocumentController.cs b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileDocumentController.cs
index fc2801d171..2ecfd021c1 100644
--- a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileDocumentController.cs
+++ b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileDocumentController.cs
@@ -110,7 +110,7 @@ namespace MonoDevelop.Ide.Gui.Documents
 					if (!typeof (FileModel).IsAssignableFrom (FileModelType))
 						throw new InvalidOperationException ("Invalid file model type: " + FileModelType);
 					var fileModel = (FileModel)Activator.CreateInstance (FileModelType);
-					fileModel.CreateNew ();
+					fileModel.CreateNew (fileDescriptor.FilePath, fileDescriptor.MimeType);
 					await fileModel.SetContent (fileDescriptor.Content);
 					if (fileDescriptor.Encoding != null && fileModel is TextFileModel textFileModel)
 						textFileModel.Encoding = fileDescriptor.Encoding;
diff --git a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileModel.cs b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileModel.cs
index 2d0b324dc6..b2c3ed6f24 100644
--- a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileModel.cs
+++ b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/FileModel.cs
@@ -41,9 +41,9 @@ namespace MonoDevelop.Ide.Gui.Documents
 		{
 		}
 
-		public string MimeType { get; set; }
+		public string MimeType => IsLoaded ? GetRepresentation<FileModelRepresentation> ().MimeType : null;
 
-		public FilePath FilePath => Id != null ? (FilePath)Id : FilePath.Null;
+		public FilePath FilePath => Id != null ? (FilePath) Id : (IsLoaded ? GetRepresentation<FileModelRepresentation> ().FilePath : FilePath.Null);
 
 		public bool CanWrite {
 			get {
@@ -57,6 +57,14 @@ namespace MonoDevelop.Ide.Gui.Documents
 			}
 		}
 
+		public void CreateNew (string fileName, string mimeType)
+		{
+			InitializeNew ();
+			var rep = GetRepresentation<FileModelRepresentation> ();
+			rep.InitUnsaved (fileName, mimeType);
+			rep.CreateNew ();
+		}
+
 		public Task LinkToFile (FilePath filePath)
 		{
 			if (FilePath != filePath)
@@ -70,10 +78,10 @@ namespace MonoDevelop.Ide.Gui.Documents
 			await UnlinkFromId ();
 		}
 
-		public Task SaveAs (FilePath filePath)
+		public async Task SaveAs (FilePath filePath)
 		{
-			LinkToFile (filePath);
-			return Save ();
+			await LinkToFile (filePath);
+			await Save ();
 		}
 
 		/// <summary>
@@ -99,9 +107,20 @@ namespace MonoDevelop.Ide.Gui.Documents
 
 		protected abstract class FileModelRepresentation : ModelRepresentation
 		{
-			public FilePath FilePath => Id != null ? (FilePath)Id : FilePath.Null;
+			FilePath unsavedFilePath;
+
+			public FilePath FilePath => Id != null ? (FilePath)Id : unsavedFilePath;
 			public string MimeType { get; set; }
 
+			internal void InitUnsaved (FilePath filePath, string mimeType)
+			{
+				unsavedFilePath = filePath;
+				if (mimeType != null)
+					MimeType = mimeType;
+				else if (!filePath.IsNullOrEmpty)
+					MimeType = Runtime.PeekService<DesktopService> ()?.GetMimeTypeForUri (filePath);
+			}
+
 			public async Task SetContent (Stream content)
 			{
 				try {
@@ -128,6 +147,11 @@ namespace MonoDevelop.Ide.Gui.Documents
 				} else
 					throw new InvalidOperationException ($"Can't copy data from model of type {other.GetType ()} into a model of type {GetType ()}");
 			}
+
+			protected override async Task OnIdChanged ()
+			{
+				MimeType = (await Runtime.GetService<DesktopService> ()).GetMimeTypeForUri (FilePath);
+			}
 		}
 
 		class InternalFileModelRepresentation : FileModelRepresentation
diff --git a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/ModelRepresentation.cs b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/ModelRepresentation.cs
index bdbde45d4c..8ca0506274 100644
--- a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/ModelRepresentation.cs
+++ b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/ModelRepresentation.cs
@@ -68,6 +68,7 @@ namespace MonoDevelop.Ide.Gui.Documents
 		{
 			try {
 				await WaitHandle.WaitAsync ();
+				await CheckIdChange ();
 				if (IsLoaded)
 					return;
 				if (DocumentModelData.IsLinked)
@@ -96,6 +97,7 @@ namespace MonoDevelop.Ide.Gui.Documents
 		{
 			try {
 				await WaitHandle.WaitAsync ();
+				await CheckIdChange ();
 				await OnLoad ();
 				IsLoaded = true;
 				HasUnsavedChanges = false;
@@ -108,6 +110,7 @@ namespace MonoDevelop.Ide.Gui.Documents
 		{
 			try {
 				await WaitHandle.WaitAsync ();
+				await CheckIdChange ();
 				await OnSave ();
 				HasUnsavedChanges = false;
 			} finally {
@@ -138,6 +141,25 @@ namespace MonoDevelop.Ide.Gui.Documents
 
 		protected abstract void OnCreateNew ();
 
+		/// <summary>
+		/// Invoked just before a load or save operation when the Id of a model has changed
+		/// </summary>
+		protected virtual Task OnIdChanged ()
+		{
+			return Task.CompletedTask;
+		}
+
+		object id;
+
+		Task CheckIdChange ()
+		{
+			if (id != Id) {
+				id = Id;
+				return OnIdChanged ();
+			} else
+				return Task.CompletedTask;
+		}
+
 		protected abstract Task OnLoad ();
 
 		protected abstract Task OnSave ();
diff --git a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/TextBufferFileModel.cs b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/TextBufferFileModel.cs
index 5b3e7db3c6..59f3193212 100644
--- a/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/TextBufferFileModel.cs
+++ b/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui.Documents/TextBufferFileModel.cs
@@ -66,8 +66,7 @@ namespace MonoDevelop.Ide.Gui.Documents
 			protected override async Task OnLoad ()
 			{
 				var text = await TextFileUtility.GetTextAsync (FilePath, CancellationToken.None);
-				MimeType = (await Runtime.GetService<DesktopService> ()).GetMimeTypeForUri (FilePath);
-				var contentType = (MimeType == null) ? PlatformCatalog.Instance.TextBufferFactoryService.InertContentType : GetContentTypeFromMimeType (FilePath, MimeType);
+				var contentType = GetContentTypeFromMimeType ();
 				if (textDocument != null) {
 					// Reloading
 					try {
@@ -115,6 +114,10 @@ namespace MonoDevelop.Ide.Gui.Documents
 
 			protected override Task OnSave ()
 			{
+				var contentType = GetContentTypeFromMimeType ();
+				if (textDocument.TextBuffer.ContentType != contentType)
+					textDocument.TextBuffer.ChangeContentType (contentType, null);
+
 				// OnLoad is always called before anything else, so the document should be ready
 				textDocument.SaveAs (FilePath, true);
 				cleanReiteratedVersion = textDocument.TextBuffer.CurrentSnapshot.Version.ReiteratedVersionNumber;
@@ -126,17 +129,18 @@ namespace MonoDevelop.Ide.Gui.Documents
 
 			ITextDocument CreateTextDocument (string text)
 			{
-				var contentType = (MimeType == null)
-					? PlatformCatalog.Instance.TextBufferFactoryService.InertContentType
-					: GetContentTypeFromMimeType (FilePath, MimeType);
+				var contentType = GetContentTypeFromMimeType ();
 				var buffer = PlatformCatalog.Instance.TextBufferFactoryService.CreateTextBuffer (text, contentType);
 				var doc = PlatformCatalog.Instance.TextDocumentFactoryService.CreateTextDocument (buffer, FilePath.ToString () ?? "");
 				return doc;
 			}
 
-			protected static IContentType GetContentTypeFromMimeType (string filePath, string mimeType)
+			IContentType GetContentTypeFromMimeType ()
 			{
-				return MimeTypeCatalog.Instance.GetContentTypeForMimeType (mimeType, filePath)
+				if (MimeType == null)
+					return PlatformCatalog.Instance.TextBufferFactoryService.InertContentType;
+
+				return MimeTypeCatalog.Instance.GetContentTypeForMimeType (MimeType, FilePath)
 					?? PlatformCatalog.Instance.ContentTypeRegistryService.GetContentType ("text");
 			}