fix: metadata update after XAML hot reload breaks compilation

Author: jeromelaban

src/SourceGenerators/Uno.UI.SourceGenerators/Content/Uno.UI.SourceGenerators.props

@@ -42,6 +42,7 @@
 		<CompilerVisibleProperty Include="BuildingProject" />
 		<CompilerVisibleProperty Include="DesignTimeBuild" />
 		<CompilerVisibleProperty Include="UnoUISourceGeneratorDebuggerBreak" />
+		<CompilerVisibleProperty Include="IsHotReloadHost" />
 
 		<CompilerVisibleProperty Include="UseWPF" />
 		<CompilerVisibleProperty Include="IsUnoHead" />

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

@@ -56,10 +56,23 @@ internal void Update(GeneratorExecutionContext context)
 				}
 			}
 
-			if(bool.TryParse(context.GetMSBuildPropertyValue("DesignTimeBuild"), out var designTimeBuild) && designTimeBuild)
+			if(GetIsDesignTimeBuild(context) && !GetIsHotReloadHost(context))
 			{
+				// Design-time builds need to clear runs for the x:Name values to be regenerated, in the context of OmniSharp.
+				// In the context of HotReload, we need to skip this, as the HotReload service sets DesignTimeBuild to build
+				// to true, preventing existing runs to be kept active.
 				_runs.Clear();
 			}
 		}
+
+		private bool GetIsDesignTimeBuild(GeneratorExecutionContext context)
+		{
+			return bool.TryParse(context.GetMSBuildPropertyValue("DesignTimeBuild"), out var value) && value;
+		}
+
+		private bool GetIsHotReloadHost(GeneratorExecutionContext context)
+		{
+			return bool.TryParse(context.GetMSBuildPropertyValue("IsHotReloadHost"), out var value) && value;
+		}
 	}
 }

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

@@ -31,7 +31,7 @@ public void Initialize(GeneratorInitializationContext context)
 		public void Execute(GeneratorExecutionContext context)
 		{
 			// No initialization required for this one
-			//if (!Process.GetCurrentProcess().ProcessName.Equals("devenv", StringComparison.OrdinalIgnoreCase))
+			//if (!Process.GetCurrentProcess().ProcessName.Equals("omnisharp.exe", StringComparison.OrdinalIgnoreCase))
 			//{
 			//	Debugger.Launch();
 			//}

src/Uno.UI.RemoteControl.Server.Processors/HotReload/MetadataUpdates/CompilationWorkspaceProvider.cs

@@ -40,6 +40,9 @@ static async void CreateProject(
 				// Override the output path so custom compilation lists do not override the
 				// main compilation caches, which can invalidate incremental compilation.
 				{ "IntermediateOutputPath", intermediatePath },
+
+				// Mark this compilation as hot-reload capable, so generators can act accordingly
+				{ "IsHotReloadHost", "True" },
 			};
 
 			var workspace = MSBuildWorkspace.Create(globalProperties);