dotnet · jonathanpeppers · Jul 29, 2026 · Jul 23, 2026 · Jul 23, 2026 · Jul 23, 2026
@@ -441,16 +441,19 @@ static unsafe IntPtr monovm_typemap_managed_to_java (Type type, byte* mvidptr)
 				return TrimmableTypeMap.Instance.TryGetJniNameForManagedType (type, out var jniName) ? jniName : null;
 			}
 
-			if (mvid_bytes == null)
-				mvid_bytes = new byte[16];
-
-			var mvid = new Span<byte>(mvid_bytes);
 			byte[]? mvid_data = null;
-			if (!type.Module.ModuleVersionId.TryWriteBytes (mvid)) {
-				RuntimeNativeMethods.monodroid_log (LogLevel.Warn, LogCategories.Default, $"Failed to obtain module MVID using the fast method, falling back to the slow one");
-				mvid_data = type.Module.ModuleVersionId.ToByteArray ();
-			} else {
-				mvid_data = mvid_bytes;
+			// The Debug CoreCLR typemaps are keyed on the assembly display name, so computing the MVID would be wasted work.
+			if (!RuntimeFeature.IsCoreClrRuntime || !RuntimeFeature.ManagedToJavaUsesAssemblyFullName) {
+				if (mvid_bytes == null)
+					mvid_bytes = new byte[16];
+
+				var mvid = new Span<byte>(mvid_bytes);
+				if (!type.Module.ModuleVersionId.TryWriteBytes (mvid)) {
+					RuntimeNativeMethods.monodroid_log (LogLevel.Warn, LogCategories.Default, $"Failed to obtain module MVID using the fast method, falling back to the slow one");
+					mvid_data = type.Module.ModuleVersionId.ToByteArray ();
+				} else {
+					mvid_data = mvid_bytes;
+				}
 			}
 
 			IntPtr ret;
@@ -460,7 +463,8 @@ static unsafe IntPtr monovm_typemap_managed_to_java (Type type, byte* mvidptr)
 				} else if (RuntimeFeature.IsCoreClrRuntime) {
 					if (type.FullName is null)
 						return null;
-					ret = RuntimeNativeMethods.clr_typemap_managed_to_java (type.FullName, (IntPtr)mvidptr);
+					string? assemblyFullName = RuntimeFeature.ManagedToJavaUsesAssemblyFullName ? type.Assembly.FullName : null;
+					ret = RuntimeNativeMethods.clr_typemap_managed_to_java (type.FullName, assemblyFullName, (IntPtr)mvidptr);
 				} else {
 					throw new NotSupportedException ("Internal error: unknown runtime not supported");
 				}

@@ -115,7 +115,7 @@ internal unsafe static partial class RuntimeNativeMethods
 
 		[LibraryImport (RuntimeConstants.InternalDllName, StringMarshalling = StringMarshalling.Utf8)]
 		[UnmanagedCallConv (CallConvs = new[] { typeof (CallConvCdecl) })]
-		internal static partial IntPtr clr_typemap_managed_to_java (string fullName, IntPtr mvid);
+		internal static partial IntPtr clr_typemap_managed_to_java (string fullName, string? assemblyFullName, IntPtr mvid);
 
 		[LibraryImport (RuntimeConstants.InternalDllName, StringMarshalling = StringMarshalling.Utf8)]
 		[UnmanagedCallConv (CallConvs = new[] { typeof (CallConvCdecl) })]

@@ -12,6 +12,7 @@ static class RuntimeFeature
 	const bool StartupHookSupportEnabledByDefault = true;
 	const bool TrimmableTypeMapEnabledByDefault = false;
 	const bool ObjectReferenceLoggingEnabledByDefault = false;
+	const bool ManagedToJavaUsesAssemblyFullNameEnabledByDefault = false;
 
 	const string FeatureSwitchPrefix = "Microsoft.Android.Runtime.RuntimeFeature.";
 	const string StartupHookProviderSwitch = "System.StartupHookProvider.IsSupported";
@@ -44,4 +45,9 @@ static class RuntimeFeature
 	[FeatureSwitchDefinition ($"{FeatureSwitchPrefix}{nameof (ObjectReferenceLogging)}")]
 	internal static bool ObjectReferenceLogging { get; } =
 		AppContext.TryGetSwitch ($"{FeatureSwitchPrefix}{nameof (ObjectReferenceLogging)}", out bool isEnabled) ? isEnabled : ObjectReferenceLoggingEnabledByDefault;
+
+	// Enabled for Debug builds, whose string-based typemaps support Fast Deployment without embedding assembly MVIDs.
+	[FeatureSwitchDefinition ($"{FeatureSwitchPrefix}{nameof (ManagedToJavaUsesAssemblyFullName)}")]
+	internal static bool ManagedToJavaUsesAssemblyFullName { get; } =
+		AppContext.TryGetSwitch ($"{FeatureSwitchPrefix}{nameof (ManagedToJavaUsesAssemblyFullName)}", out bool isEnabled) ? isEnabled : ManagedToJavaUsesAssemblyFullNameEnabledByDefault;
 }
@@ -37,6 +37,7 @@ public void ProcessAssembly (AssemblyDefinition assembly, StepContext context)
 
 		var xml = new TypeMapObjectsXmlFile {
 			AssemblyName = assembly.Name.Name,
+			AssemblyFullName = Debug ? TypeMapCecilAdapter.GetRuntimeAssemblyFullName (assembly.Name) : null,
 			AssemblyMvid = assembly.MainModule.Mvid,
 		};
 

@@ -34,6 +34,10 @@ This file contains the CoreCLR-specific MSBuild logic for .NET for Android.
         Value="false"
         Trim="true"
     />
+    <RuntimeHostConfigurationOption Include="Microsoft.Android.Runtime.RuntimeFeature.ManagedToJavaUsesAssemblyFullName"
+        Value="$(AndroidIncludeDebugSymbols)"
+        Trim="true"
+    />
   </ItemGroup>
 
   <Target Name="_CLRUseLocalRuntimePacks" AfterTargets="ResolveFrameworkReferences"

@@ -66,13 +66,11 @@ string GenerateStubLlvmIr (string abi)
 
 		if (Debug) {
 			return header + """
-%struct.TypeMap = type { i32, i32, ptr, ptr }
-%struct.TypeMapManagedTypeInfo = type { i64, i32, i32 }
-%struct.TypeMapAssembly = type { [16 x i8], i64, i64 }
+%struct.TypeMap = type { i32, ptr, ptr }
+%struct.TypeMapManagedTypeInfo = type { i32, i32 }
 
 @type_map = dso_local constant %struct.TypeMap zeroinitializer, align 8
 @type_map_managed_type_info = dso_local constant [0 x %struct.TypeMapManagedTypeInfo] zeroinitializer, align 8
-@type_map_unique_assemblies = dso_local constant [0 x %struct.TypeMapAssembly] zeroinitializer, align 8
 @type_map_assembly_names = dso_local constant [1 x i8] zeroinitializer, align 1
 @type_map_managed_type_names = dso_local constant [1 x i8] zeroinitializer, align 1
 @type_map_java_type_names = dso_local constant [1 x i8] zeroinitializer, align 1

@@ -1390,6 +1390,32 @@ public void GenerateJavaStubsAndAssembly ([Values] bool isRelease, [Values (Andr
 					Assert.IsTrue (b.Output.IsTargetSkipped (target), $"`{target}` should be skipped!");
 				}
 				AssertAssemblyFilesInFileWrites (proj, b, abi, runtime);
+
+				if (!isRelease && runtime == AndroidRuntime.CoreCLR) {
+					string projectDirectory = Path.Combine (Root, b.ProjectDirectory);
+					string intermediate = Path.Combine (projectDirectory, proj.IntermediateOutputPath, MonoAndroidHelper.AbiToRid (abi));
+					string typemap = Path.Combine (intermediate, "android", $"typemaps.{abi}.ll");
+					string apk = Directory.GetFiles (Path.Combine (projectDirectory, proj.OutputPath), "*-Signed.apk", SearchOption.AllDirectories).Single ();
+					DateTime typemapWriteTime = File.GetLastWriteTimeUtc (typemap);
+					DateTime apkWriteTime = File.GetLastWriteTimeUtc (apk);
+					string typemapHash = Files.HashFile (typemap);
+					string apkHash = Files.HashFile (apk);
+
+					// Change managed code without changing any Java type mappings.
+					proj.MainActivity = proj.MainActivity.Replace ("clicks", "CLICKS");
+					proj.Touch ("MainActivity.cs");
+					Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "fourth build should have succeeded.");
+
+					b.Output.AssertTargetIsNotSkipped ("CoreCompile");
+					b.Output.AssertTargetIsSkipped ("_CompileNativeAssemblySources");
+					b.Output.AssertTargetIsSkipped ("_CreateApplicationSharedLibraries");
+					b.Output.AssertTargetIsSkipped ("_BuildApkFastDev");
+					b.Output.AssertTargetIsSkipped ("_Sign");
+					Assert.AreEqual (typemapWriteTime, File.GetLastWriteTimeUtc (typemap), $"{typemap} should not be rewritten when its mappings have not changed.");
+					Assert.AreEqual (typemapHash, Files.HashFile (typemap), $"{typemap} contents should not change.");
+					Assert.AreEqual (apkWriteTime, File.GetLastWriteTimeUtc (apk), $"{apk} should not be rewritten for an incremental C# change.");
+					Assert.AreEqual (apkHash, Files.HashFile (apk), $"{apk} contents should not change.");
+				}
 			}
 		}
 

@@ -2,7 +2,9 @@
 using System.Collections.Generic;
 using System.IO;
 using Microsoft.Build.Utilities;
+using Mono.Cecil;
 using NUnit.Framework;
+using Xamarin.Android.Tasks;
 using Xamarin.Android.Tasks.LLVMIR;
 using Xamarin.Android.Tools;
 
@@ -79,5 +81,27 @@ public void GeneratedIR_FunctionWithWhitespaceParameterName_ProducesValidOutput
 			Assert.That (output, Does.Not.Contain ("%\t)"), "Generated LLVM IR should not contain 'ptr noundef %\\t)' pattern");
 			Assert.That (output, Does.Contain ("@test_function"), "Generated LLVM IR should contain the function name");
 		}
+
+		[Test]
+		public void TypeMapAssemblyFullNameUsesRuntimeEscaping ()
+		{
+			var assemblyName = new AssemblyNameDefinition ("Comma,Name", new Version (1, 2, 3, 4));
+
+			Assert.That (
+				TypeMapCecilAdapter.GetRuntimeAssemblyFullName (assemblyName),
+				Is.EqualTo (@"Comma\,Name, Version=1.2.3.4, Culture=neutral, PublicKeyToken=null")
+			);
+		}
+
+		[Test]
+		public void TypeMapAssemblyFullNameMatchesStrongNamedRuntimeAssembly ()
+		{
+			string assemblyPath = typeof (TypeMapCecilAdapter).Assembly.Location;
+			using var assembly = AssemblyDefinition.ReadAssembly (assemblyPath);
+			string? runtimeFullName = System.Reflection.AssemblyName.GetAssemblyName (assemblyPath).FullName;
+
+			Assert.That (runtimeFullName, Does.Not.EndWith ("PublicKeyToken=null"));
+			Assert.That (TypeMapCecilAdapter.GetRuntimeAssemblyFullName (assembly.Name), Is.EqualTo (runtimeFullName));
+		}
 	}
 }
@@ -3,6 +3,7 @@
 using System.IO;
 using System.Linq;
 using System.Text.RegularExpressions;
+using Microsoft.Build.Framework;
 using Xamarin.Tools.Zip;
 
 namespace Xamarin.ProjectTools
@@ -170,8 +171,27 @@ public TimeSpan GetTargetOrTaskTime (string targetOrTask)
 			return TimeSpan.Zero;
 		}
 
+		/// <summary>
+		/// Gets a value indicating whether the .apk was installed on the device by the last build.
+		/// </summary>
+		/// <remarks>
+		/// <para>This scans the build output for the <c>Installed Package</c> message written by the
+		/// <c>FastDeploy</c> and <c>FastDeploy2</c> tasks. Both write it with
+		/// <see cref="Microsoft.Build.Framework.MessageImportance.Low"/>, so it is only present in the
+		/// build output at <see cref="Microsoft.Build.Framework.LoggerVerbosity.Detailed"/> or higher.</para>
+		/// <para>At a lower verbosity this property would silently return <c>false</c> no matter what the
+		/// build did, which makes both <c>Assert.IsTrue</c> and <c>Assert.IsFalse</c> on it meaningless.
+		/// It therefore throws instead, so the test fails with an actionable message rather than a
+		/// misleading pass or an opaque assertion failure.</para>
+		/// </remarks>
+		/// <exception cref="InvalidOperationException">
+		/// <see cref="Builder"/> is running at a verbosity below
+		/// <see cref="Microsoft.Build.Framework.LoggerVerbosity.Detailed"/>.
+		/// </exception>
 		public bool IsApkInstalled {
 			get {
+				if (Builder.Verbosity < LoggerVerbosity.Detailed)
+					throw new InvalidOperationException ($"`{nameof (IsApkInstalled)}` requires `{nameof (Builder)}.{nameof (Builder.Verbosity)}` to be `{nameof (LoggerVerbosity.Detailed)}` or higher, but it is `{Builder.Verbosity}`. The `Installed Package` message it looks for is logged with `MessageImportance.Low`.");
 				foreach (var line in Builder.LastBuildOutput) {
 					if (line.Contains ("Installed Package") || line.Contains (" pm install "))
 						return true;

@@ -3,6 +3,9 @@
 using Java.Interop.Tools.Cecil;
 using Mono.Cecil;
 
+using ReflectionAssemblyContentType = System.Reflection.AssemblyContentType;
+using ReflectionAssemblyName = System.Reflection.AssemblyName;
+using ReflectionAssemblyNameFlags = System.Reflection.AssemblyNameFlags;
 using ModuleReleaseData = Xamarin.Android.Tasks.TypeMapGenerator.ModuleReleaseData;
 using ReleaseGenerationState = Xamarin.Android.Tasks.TypeMapGenerator.ReleaseGenerationState;
 using TypeMapDebugEntry = Xamarin.Android.Tasks.TypeMapGenerator.TypeMapDebugEntry;
@@ -149,9 +152,25 @@ static TypeMapDebugEntry GetDebugEntry (TypeDefinition td, TypeDefinitionCache c
 			TypeDefinition = td,
 			SkipInJavaToManaged = ShouldSkipInJavaToManaged (td),
 			AssemblyName = td.Module.Assembly.Name.Name,
+			AssemblyFullName = GetRuntimeAssemblyFullName (td.Module.Assembly.Name),
 		};
 	}
 
+	// Cecil's FullName does not escape assembly display names in the same way as Assembly.FullName.
+	public static string GetRuntimeAssemblyFullName (AssemblyNameReference assemblyName)
+	{
+		var runtimeAssemblyName = new ReflectionAssemblyName {
+			Name = assemblyName.Name,
+			Version = assemblyName.Version,
+			CultureName = assemblyName.Culture ?? "",
+			Flags = assemblyName.IsRetargetable ? ReflectionAssemblyNameFlags.Retargetable : ReflectionAssemblyNameFlags.None,
+			ContentType = assemblyName.IsWindowsRuntime ? ReflectionAssemblyContentType.WindowsRuntime : ReflectionAssemblyContentType.Default,
+		};
+		runtimeAssemblyName.SetPublicKeyToken (assemblyName.PublicKeyToken);
+
+		return runtimeAssemblyName.FullName ?? throw new InvalidOperationException ($"Unable to format assembly name '{assemblyName.Name}'.");
+	}
+
 	static string GetManagedTypeName (TypeDefinition td)
 	{
 		// This is necessary because Mono runtime will return to us type name with a `.` for nested types (not a

@@ -64,6 +64,7 @@ internal sealed class TypeMapDebugEntry
 			public bool SkipInJavaToManaged;
 			public TypeMapDebugEntry DuplicateForJavaToManaged;
 			public string AssemblyName;
+			public string AssemblyFullName;
 
 			// This field is only used by the Cecil adapter for temp storage while reading.
 			// It is not used to create the typemap.

@@ -23,6 +23,7 @@ class TypeMapObjectsXmlFile
 	static readonly TypeMapObjectsXmlFile unscanned = new TypeMapObjectsXmlFile { WasScanned = false };
 
 	public string? AssemblyName { get; set; }
+	public string? AssemblyFullName { get; set; }
 	public Guid AssemblyMvid { get; set; } = Guid.Empty;
 	public bool FoundJniNativeRegistration { get; set; }
 	public List<TypeMapDebugEntry> JavaToManagedDebugEntries { get; } = [];
@@ -57,6 +58,7 @@ void Export (XmlWriter xml)
 		xml.WriteStartElement ("api");
 		xml.WriteAttributeString ("type", HasDebugEntries ? "debug" : "release");
 		xml.WriteAttributeStringIfNotDefault ("assembly-name", AssemblyName);
+		xml.WriteAttributeStringIfNotDefault ("assembly-full-name", AssemblyFullName);
 
 		if (AssemblyMvid != Guid.Empty) {
 			xml.WriteAttributeString ("mvid", AssemblyMvid.ToString ("N"));
@@ -183,13 +185,15 @@ public static TypeMapObjectsXmlFile Import (string filename)
 			throw new InvalidOperationException ($"Missing required attribute 'type' in '{filename}'");
 
 		var assemblyName = reader.GetAttribute ("assembly-name");
+		var assemblyFullName = reader.GetAttribute ("assembly-full-name");
 		var mvidValue = reader.GetAttribute ("mvid");
 		var mvid = mvidValue.IsNullOrWhiteSpace () ? Guid.Empty : Guid.Parse (mvidValue);
 		var foundJniNativeRegistration = GetAttributeOrDefault (reader, "found-jni-native-registration", false);
 
 		var file = new TypeMapObjectsXmlFile {
 			WasScanned = true,
 			AssemblyName = assemblyName,
+			AssemblyFullName = assemblyFullName,
 			AssemblyMvid = mvid,
 			FoundJniNativeRegistration = foundJniNativeRegistration,
 		};
@@ -205,16 +209,17 @@ public static TypeMapObjectsXmlFile Import (string filename)
 	static void ImportDebugData (XmlReader reader, TypeMapObjectsXmlFile file)
 	{
 		var assemblyName = file.AssemblyName ?? string.Empty;
+		var assemblyFullName = file.AssemblyFullName ?? string.Empty;
 		var isMonoAndroid = assemblyName == "Mono.Android";
 
 		while (reader.Read ()) {
 			if (reader.NodeType != XmlNodeType.Element)
 				continue;
 
 			if (reader.Name == "java-to-managed")
-				ReadDebugEntries (reader, file.JavaToManagedDebugEntries, assemblyName, isMonoAndroid);
+				ReadDebugEntries (reader, file.JavaToManagedDebugEntries, assemblyName, assemblyFullName, isMonoAndroid);
 			else if (reader.Name == "managed-to-java")
-				ReadDebugEntries (reader, file.ManagedToJavaDebugEntries, assemblyName, isMonoAndroid);
+				ReadDebugEntries (reader, file.ManagedToJavaDebugEntries, assemblyName, assemblyFullName, isMonoAndroid);
 		}
 	}
 
@@ -268,7 +273,7 @@ public static void WriteEmptyFile (string destination, TaskLoggingHelper log)
 		File.Create (destination).Dispose ();
 	}
 
-	static TypeMapDebugEntry FromDebugEntryXml (XmlReader reader, string assemblyName, bool isMonoAndroid)
+	static TypeMapDebugEntry FromDebugEntryXml (XmlReader reader, string assemblyName, string assemblyFullName, bool isMonoAndroid)
 	{
 		return new TypeMapDebugEntry {
 			JavaName = reader.GetAttribute ("java-name") ?? string.Empty,
@@ -278,6 +283,7 @@ static TypeMapDebugEntry FromDebugEntryXml (XmlReader reader, string assemblyNam
 			IsInvoker = GetAttributeOrDefault (reader, "is-invoker", false),
 			IsMonoAndroid = isMonoAndroid,
 			AssemblyName = assemblyName,
+			AssemblyFullName = assemblyFullName,
 		};
 	}
 
@@ -301,7 +307,7 @@ static T GetAttributeOrDefault<T> (XmlReader reader, string name, T defaultValue
 		return (T) Convert.ChangeType (value, typeof (T), CultureInfo.InvariantCulture);
 	}
 
-	static void ReadDebugEntries (XmlReader reader, List<TypeMapDebugEntry> entries, string assemblyName, bool isMonoAndroid)
+	static void ReadDebugEntries (XmlReader reader, List<TypeMapDebugEntry> entries, string assemblyName, string assemblyFullName, bool isMonoAndroid)
 	{
 		if (reader.IsEmptyElement)
 			return;
@@ -313,7 +319,7 @@ static void ReadDebugEntries (XmlReader reader, List<TypeMapDebugEntry> entries,
 				return;
 
 			if (reader.NodeType == XmlNodeType.Element && reader.Name == "entry")
-				entries.Add (FromDebugEntryXml (reader, assemblyName, isMonoAndroid));
+				entries.Add (FromDebugEntryXml (reader, assemblyName, assemblyFullName, isMonoAndroid));
 		}
 	}