feat: Improve error reporting with Roslyn-hosted generators

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

@@ -1,4 +1,5 @@
-#nullable enable
+extern alias __uno;
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -15,6 +16,8 @@
 using Uno.UI.SourceGenerators.Telemetry;
 using Uno.UI.Xaml;
 using System.Drawing;
+using __uno::Uno.Xaml;
+using Microsoft.CodeAnalysis.Text;
 
 #if NETFRAMEWORK
 using Microsoft.Build.Execution;
@@ -49,6 +52,23 @@ internal partial class XamlCodeGeneration
 		private readonly bool _outputSourceComments = true;
 		private readonly RoslynMetadataHelper _metadataHelper;
 
+		internal const string Title = "XAML Generation Failed";
+		internal const string MessageFormat = "{0}";
+		internal const string Description = "XAML Generation Failed";
+		internal const string Category = "XAML";
+
+		internal static DiagnosticDescriptor GenericXamlErrroRule = new DiagnosticDescriptor(
+#pragma warning disable RS2008 // Enable analyzer release tracking
+			"UXAML0001",
+#pragma warning restore RS2008 // Enable analyzer release tracking
+			Title,
+			MessageFormat,
+			Category,
+			DiagnosticSeverity.Error,
+			isEnabledByDefault: true,
+			description: Description
+		);
+
 		/// <summary>
 		/// If set, code generated from XAML will be annotated with the source method and line # in XamlFileGenerator, for easier debugging.
 		/// </summary>
@@ -316,7 +336,11 @@ public KeyValuePair<string, string>[] Generate()
 			{
 				TrackGenerationFailed(e, stopwatch.Elapsed);
 
+#if NETFRAMEWORK
 				throw;
+#else
+				return ProcessParsingException(e);
+#endif
 			}
 			finally
 			{
@@ -325,6 +349,74 @@ public KeyValuePair<string, string>[] Generate()
 			}
 		}
 
+		private KeyValuePair<string, string>[] ProcessParsingException(Exception e)
+		{
+			IEnumerable<Exception> Flatten(Exception ex)
+			{
+				if (ex is AggregateException agg)
+				{
+					foreach (var inner in agg.InnerExceptions)
+					{
+						foreach (var inner2 in Flatten(inner))
+						{
+							yield return inner2;
+						}
+					}
+				}
+				else
+				{
+					if (ex.InnerException != null)
+					{
+						foreach (var inner2 in Flatten(ex.InnerException))
+						{
+							yield return inner2;
+						}
+					}
+
+					yield return ex;
+				}
+			}
+
+			foreach (var exception in Flatten(e))
+			{
+				var diagnostic = Diagnostic.Create(
+					GenericXamlErrroRule,
+					GetExceptionFileLocation(exception),
+					exception.Message);
+
+				_generatorContext.ReportDiagnostic(diagnostic);
+			}
+
+			return new KeyValuePair<string, string>[0];
+		}
+
+		private Location? GetExceptionFileLocation(Exception exception)
+		{
+			if (exception is XamlParsingException xamlParsingException)
+			{
+				var xamlFile = _generatorContext.AdditionalFiles.FirstOrDefault(f => f.Path == xamlParsingException.FilePath);
+
+				if (xamlFile != null
+					&& xamlFile.GetText() is { } xamlText
+					&& xamlParsingException.LineNumber.HasValue
+					&& xamlParsingException.LinePosition.HasValue)
+				{
+					var linePosition = new LinePosition(
+						Math.Max(0, xamlParsingException.LineNumber.Value - 1),
+						Math.Max(0, xamlParsingException.LinePosition.Value - 1)
+					);
+
+					return Location.Create(
+						xamlFile.Path,
+						xamlText.Lines.ElementAtOrDefault(xamlParsingException.LineNumber.Value-1).Span,
+						new LinePositionSpan(linePosition, linePosition)
+					);
+				}
+			}
+
+			return null;
+		}
+
 		private XamlGlobalStaticResourcesMap BuildAssemblyGlobalStaticResourcesMap(XamlFileDefinition[] files, XamlFileDefinition[] filesFull, string[] links)
 		{
 			var map = new XamlGlobalStaticResourcesMap();

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

@@ -2269,6 +2269,7 @@ implicitContentChild.Value is string implicitValue
 			}
 			catch (Exception e)
 			{
+#if NETFRAMEWORK
 				throw new InvalidOperationException(
 					"An error occurred when processing {0} at line {1}:{2} ({3}) : {4}"
 					.InvariantCultureFormat(
@@ -2280,6 +2281,15 @@ implicitContentChild.Value is string implicitValue
 					)
 					, e
 				);
+#else
+				throw new XamlParsingException(
+					$"An error was found in {topLevelControl.Type.Name}"
+					, e
+					, topLevelControl.LineNumber
+					, topLevelControl.LinePosition
+					, _fileDefinition.FilePath
+				);
+#endif
 			}
 		}
 

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

@@ -1,4 +1,5 @@
-#nullable enable
+extern alias __uno;
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -70,9 +71,17 @@ public XamlFileDefinition[] ParseFiles(string[] xamlSourceFiles)
 
 				return null;
 			}
+			catch (__uno::Uno.Xaml.XamlParseException e)
+			{
+				throw new XamlParsingException(e.Message, null, e.LineNumber, e.LinePosition, file);
+			}
+			catch (XmlException e)
+			{
+				throw new XamlParsingException(e.Message, null, e.LineNumber, e.LinePosition, file);
+			}
 			catch (Exception e)
 			{
-				throw new InvalidOperationException($"Failed to parse file {file}", e);
+				throw new XamlParsingException($"Failed to parse file", e, 1, 1, file);
 			}
 		}
 

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

@@ -0,0 +1,37 @@
+#nullable enable
+
+using System;
+using System.Runtime.Serialization;
+
+namespace Uno.UI.SourceGenerators.XamlGenerator
+{
+	/// <summary>
+	/// Defines a XAML parsing exception to be raised from the generator
+	/// </summary>
+	[Serializable]
+	internal class XamlParsingException : Exception
+	{
+		public XamlParsingException()
+		{
+		}
+
+		public XamlParsingException(string message) : base(message)
+		{
+		}
+
+		public XamlParsingException(string message, Exception? innerException, int lineNumber, int linePosition, string filePath) : base(message, innerException)
+		{
+			LineNumber = lineNumber;
+			LinePosition = linePosition;
+			FilePath = filePath;
+		}
+
+		protected XamlParsingException(SerializationInfo info, StreamingContext context) : base(info, context)
+		{
+		}
+
+		public int? LineNumber { get; }
+		public int? LinePosition { get; }
+		public string? FilePath { get; }
+	}
+}