fix: Add XAML source generator cancellation support

Author: jeromelaban

src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlCodeGeneration.cs

@@ -256,7 +256,8 @@ public KeyValuePair<string, string>[] Generate()
 				var lastBinaryUpdateTime = _forceGeneration ? DateTime.MaxValue : GetLastBinaryUpdateTime();
 
 				var resourceKeys = GetResourceKeys();
-				var filesFull = new XamlFileParser(_excludeXamlNamespaces, _includeXamlNamespaces, _metadataHelper).ParseFiles(_xamlSourceFiles);
+				var filesFull = new XamlFileParser(_excludeXamlNamespaces, _includeXamlNamespaces, _metadataHelper)
+					.ParseFiles(_xamlSourceFiles, _generatorContext.CancellationToken);
 				var files = filesFull
 					.Trim()
 					.OrderBy(f => f.UniqueID)
@@ -277,6 +278,11 @@ public KeyValuePair<string, string>[] Generate()
 
 				var filesToProcess = filesQuery.AsParallel();
 
+#if NETSTANDARD2_0
+				filesToProcess = filesToProcess
+					.WithCancellation(_generatorContext.CancellationToken);
+#endif
+
 				if (Debugger.IsAttached)
 				{
 					filesToProcess = filesToProcess

src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileParser.cs

@@ -34,18 +34,19 @@ public XamlFileParser(string[] excludeXamlNamespaces, string[] includeXamlNamesp
 			this._metadataHelper = roslynMetadataHelper;
 		}
 
-		public XamlFileDefinition[] ParseFiles(string[] xamlSourceFiles)
+		public XamlFileDefinition[] ParseFiles(string[] xamlSourceFiles, System.Threading.CancellationToken cancellationToken)
 		{
 			var files = new List<XamlFileDefinition>();
 
 			return xamlSourceFiles
 				.AsParallel()
-				.Select(ParseFile)
+				.WithCancellation(cancellationToken)
+				.Select(f => ParseFile(f, cancellationToken))
 				.Where(f => f != null)
 				.ToArray()!;
 		}
 
-		private XamlFileDefinition? ParseFile(string file)
+		private XamlFileDefinition? ParseFile(string file, System.Threading.CancellationToken cancellationToken)
 		{
 			try
 			{
@@ -65,6 +66,8 @@ public XamlFileDefinition[] ParseFiles(string[] xamlSourceFiles)
 				{
 					if (reader.Read())
 					{
+						cancellationToken.ThrowIfCancellationRequested();
+
 						return Visit(reader, file);
 					}
 				}