Add host option to disable AssemblyLoadContext

Mono.TextTemplating/Mono.TextTemplating.CodeCompilation/CompiledAssemblyData.cs

@@ -38,7 +38,7 @@ public Assembly LoadInAssemblyLoadContext (AssemblyLoadContext loadContext)
 				return loadContext.LoadFromStream (new MemoryStream (Assembly));
 			}
 		}
-#else
+#endif
 		public Assembly LoadInCurrentAppDomain ()
 		{
 			if (DebugSymbols != null) {
@@ -47,6 +47,5 @@ public Assembly LoadInCurrentAppDomain ()
 				return System.Reflection.Assembly.Load (Assembly);
 			}
 		}
-#endif
 	}
 }

Mono.TextTemplating/Mono.TextTemplating/CompiledTemplate.TemplateAssemblyContext.cs

@@ -11,21 +11,51 @@ namespace Mono.TextTemplating;
 
 partial class CompiledTemplate
 {
-	[SuppressMessage ("Performance", "CA1822:Mark members as static", Justification = "Same API for ALC and AppDomain build variants of the class")]
-	sealed class TemplateAssemblyContext : IDisposable
+	/// <summary>
+	/// Abstracts over loading assemblies into an AssemblyLoadContext or AppDomain
+	/// and resolving assemblies from the host.
+	/// </summary>
+	abstract class TemplateAssemblyContext : IDisposable
 	{
+		public abstract Assembly LoadAssemblyFile (string assemblyPath);
+		public abstract Assembly LoadInMemoryAssembly (CompiledAssemblyData assemblyData);
+		public virtual void Dispose () { }
+
+		[SuppressMessage ("Performance", "CA1859:Use concrete types when possible for improved performance", Justification = "Conditionally compiled version of this returns multiple concrete types")]
+
+		public static TemplateAssemblyContext Create (ITextTemplatingEngineHost host, string[] referenceAssemblyFiles)
+		{
+#if FEATURE_ASSEMBLY_LOAD_CONTEXT
+			if (!host.IsAssemblyLoadContextDisabled ()) {
+				return new AssemblyLoadContextTemplateAssemblyContext (host, referenceAssemblyFiles);
+			}
+#endif
+			return new CurrentAppDomainTemplateAssemblyContext (host, referenceAssemblyFiles);
+		}
+	}
+
 #if FEATURE_ASSEMBLY_LOAD_CONTEXT
+	sealed class AssemblyLoadContextTemplateAssemblyContext : TemplateAssemblyContext
+	{
 		readonly TemplateAssemblyLoadContext templateContext;
-		public TemplateAssemblyContext (ITextTemplatingEngineHost host, string[] referenceAssemblyFiles) => templateContext = new (referenceAssemblyFiles, host);
-		public Assembly LoadAssemblyFile (string assemblyPath) => templateContext.LoadFromAssemblyPath (assemblyPath);
-		public Assembly LoadInMemoryAssembly (CompiledAssemblyData assemblyData) => assemblyData.LoadInAssemblyLoadContext (templateContext);
-		public void Dispose () { }
-#else
-		readonly CurrentDomainAssemblyResolver assemblyResolver;
-		public TemplateAssemblyContext (ITextTemplatingEngineHost host, string[] referenceAssemblyFiles) => assemblyResolver = new (referenceAssemblyFiles, host.ResolveAssemblyReference);
-		public Assembly LoadAssemblyFile (string assemblyPath) => Assembly.LoadFile (assemblyPath);
-		public Assembly LoadInMemoryAssembly (CompiledAssemblyData assemblyData) => assemblyData.LoadInCurrentAppDomain ();
-		public void Dispose () => assemblyResolver.Dispose ();
+		public AssemblyLoadContextTemplateAssemblyContext (ITextTemplatingEngineHost host, string[] referenceAssemblyFiles)
+			=> templateContext = new (referenceAssemblyFiles, host);
+		public override Assembly LoadAssemblyFile (string assemblyPath) => templateContext.LoadFromAssemblyPath (assemblyPath);
+		public override Assembly LoadInMemoryAssembly (CompiledAssemblyData assemblyData) => assemblyData.LoadInAssemblyLoadContext (templateContext);
+	}
 #endif
+
+	sealed class CurrentAppDomainTemplateAssemblyContext : TemplateAssemblyContext
+	{
+		readonly CurrentDomainAssemblyResolver assemblyResolver;
+		public CurrentAppDomainTemplateAssemblyContext (ITextTemplatingEngineHost host, string[] referenceAssemblyFiles)
+			=> assemblyResolver = new (referenceAssemblyFiles, host.ResolveAssemblyReference);
+		public override Assembly LoadAssemblyFile (string assemblyPath) => Assembly.LoadFile (assemblyPath);
+		public override Assembly LoadInMemoryAssembly (CompiledAssemblyData assemblyData) => assemblyData.LoadInCurrentAppDomain ();
+		public override void Dispose ()
+		{
+			base.Dispose ();
+			assemblyResolver.Dispose ();
+		}
 	}
 }

Mono.TextTemplating/Mono.TextTemplating/CompiledTemplate.TemplateExecutor.cs

@@ -19,7 +19,7 @@ class TemplateProcessor : MarshalByRefObject
 		[SuppressMessage ("Performance", "CA1822:Mark members as static", Justification = "Needs to be an instance for MarshalByRefObject")]
 		public string CreateAndProcess (ITextTemplatingEngineHost host, CompiledAssemblyData templateAssemblyData, string templateAssemblyFile, string fullName, CultureInfo culture, string[] referencedAssemblyFiles)
 		{
-			using var context = new TemplateAssemblyContext (host, referencedAssemblyFiles);
+			using var context = TemplateAssemblyContext.Create (host, referencedAssemblyFiles);
 
 			Assembly assembly = templateAssemblyData is not null
 				? context.LoadInMemoryAssembly (templateAssemblyData)

Mono.TextTemplating/Mono.TextTemplating/CurrentDomainAssemblyResolver.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-#if !FEATURE_ASSEMBLY_LOAD_CONTEXT
-
 using System;
 using System.IO;
 using System.Reflection;
@@ -49,5 +47,3 @@ public void Dispose ()
 		}
 	}
 }
-
-#endif

Mono.TextTemplating/Mono.TextTemplating/HostOptions.cs

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using Microsoft.VisualStudio.TextTemplating;
+
+static class HostOptionExtensions
+{
+	const string DisableAlcOptionName = "DisableAssemblyLoadContext";
+
+	static bool IsOptionTrue (this ITextTemplatingEngineHost host, string optionName) =>
+		host.GetHostOption(optionName) is string optionVal
+			&& (optionVal == "1" || optionVal.Equals("true", StringComparison.OrdinalIgnoreCase));
+
+	public static bool IsAssemblyLoadContextDisabled (this ITextTemplatingEngineHost host) => host.IsOptionTrue (DisableAlcOptionName);
+}