Skip unchanged trimmable typemap assembly emission

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/MetadataHelper.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Security.Cryptography;
 using System.Text;
@@ -7,6 +8,8 @@ namespace Microsoft.Android.Sdk.TrimmableTypeMap;
 
 static class MetadataHelper
 {
+	static readonly Guid GeneratorModuleVersionId = typeof (TypeMapAssemblyGenerator).Module.ModuleVersionId;
+
 	/// <summary>
 	/// Produces a deterministic MVID by hashing the module name together with content-dependent data.
 	/// Assemblies with the same name but different content will have different MVIDs.
@@ -66,6 +69,99 @@ public static byte [] ComputeContentFingerprint (TypeMapAssemblyData data)
 		return sha.ComputeHash (stream.GetBuffer (), 0, checked ((int) stream.Length));
 	}
 
+	/// <summary>
+	/// Computes a fingerprint of every input that affects a generated per-assembly typemap.
+	/// Unlike <see cref="ComputeContentFingerprint"/>, this is an incremental-build contract,
+	/// so it includes the generator binary identity and all model fields consumed by the emitter.
+	/// </summary>
+	public static byte [] ComputeIncrementalFingerprint (TypeMapAssemblyData data, Version systemRuntimeVersion, bool useSharedTypemapUniverse)
+	{
+		using var sha = SHA256.Create ();
+		using var stream = new MemoryStream ();
+		using var writer = new BinaryWriter (stream, Encoding.UTF8);
+		writer.Write (GeneratorModuleVersionId.ToByteArray ());
+		writer.Write (systemRuntimeVersion.ToString ());
+		writer.Write (useSharedTypemapUniverse);
+		writer.Write (data.AssemblyName);
+		writer.Write (data.ModuleName);
+		writer.Write (data.Entries.Count);
+		foreach (var entry in data.Entries) {
+			writer.Write (entry.MapKey);
+			writer.Write (entry.ProxyTypeReference);
+			writer.WriteOptionalString (entry.TargetTypeReference);
+		}
+		writer.Write (data.ProxyTypes.Count);
+		foreach (var proxy in data.ProxyTypes) {
+			writer.Write (proxy.TypeName);
+			writer.Write (proxy.JniName);
+			writer.Write (proxy.Namespace);
+			writer.WriteTypeRef (proxy.TargetType);
+			writer.WriteOptionalTypeRef (proxy.InvokerType);
+			writer.Write (proxy.InvokerActivationCtorStyle.HasValue);
+			if (proxy.InvokerActivationCtorStyle.HasValue) {
+				writer.Write ((byte) proxy.InvokerActivationCtorStyle.Value);
+			}
+			writer.WriteOptionalActivationCtor (proxy.ActivationCtor);
+			writer.Write (proxy.IsGenericDefinition);
+			writer.Write (proxy.CannotRegisterInStaticConstructor);
+			writer.Write (proxy.IsAcw);
+			writer.Write (proxy.UcoMethods.Count);
+			foreach (var method in proxy.UcoMethods) {
+				writer.WriteUcoMethod (method);
+			}
+			writer.Write (proxy.UcoConstructors.Count);
+			foreach (var constructor in proxy.UcoConstructors) {
+				writer.WriteUcoConstructor (constructor);
+			}
+			writer.Write (proxy.NativeRegistrations.Count);
+			foreach (var registration in proxy.NativeRegistrations) {
+				writer.WriteNativeRegistration (registration);
+			}
+		}
+		writer.Write (data.Associations.Count);
+		foreach (var assoc in data.Associations) {
+			writer.Write (assoc.SourceTypeReference);
+			writer.Write (assoc.AliasProxyTypeReference);
+		}
+		writer.Write (data.AliasHolders.Count);
+		foreach (var holder in data.AliasHolders) {
+			writer.Write (holder.TypeName);
+			writer.Write (holder.Namespace);
+			writer.Write (holder.AliasKeys.Count);
+			foreach (var aliasKey in holder.AliasKeys) {
+				writer.Write (aliasKey);
+			}
+		}
+		writer.Write (data.IgnoresAccessChecksTo.Count);
+		foreach (var assemblyName in data.IgnoresAccessChecksTo) {
+			writer.Write (assemblyName);
+		}
+		writer.Flush ();
+		return sha.ComputeHash (stream.GetBuffer (), 0, checked ((int) stream.Length));
+	}
+
+	/// <summary>
+	/// Computes a fingerprint of every input that affects the root typemap assembly.
+	/// </summary>
+	public static byte [] ComputeRootIncrementalFingerprint (
+		IReadOnlyList<string> perAssemblyTypeMapNames,
+		Version systemRuntimeVersion,
+		bool useSharedTypemapUniverse)
+	{
+		using var sha = SHA256.Create ();
+		using var stream = new MemoryStream ();
+		using var writer = new BinaryWriter (stream, Encoding.UTF8);
+		writer.Write (GeneratorModuleVersionId.ToByteArray ());
+		writer.Write (systemRuntimeVersion.ToString ());
+		writer.Write (useSharedTypemapUniverse);
+		writer.Write (perAssemblyTypeMapNames.Count);
+		foreach (var assemblyName in perAssemblyTypeMapNames) {
+			writer.Write (assemblyName);
+		}
+		writer.Flush ();
+		return sha.ComputeHash (stream.GetBuffer (), 0, checked ((int) stream.Length));
+	}
+
 	static void WriteTypeRef (this BinaryWriter writer, TypeRefData type)
 	{
 		writer.Write (type.ManagedTypeName);
@@ -78,15 +174,55 @@ static void WriteTypeRef (this BinaryWriter writer, TypeRefData type)
 		}
 	}
 
+	static void WriteOptionalTypeRef (this BinaryWriter writer, TypeRefData? type)
+	{
+		writer.Write (type is not null);
+		if (type is not null) {
+			writer.WriteTypeRef (type);
+		}
+	}
+
+	static void WriteOptionalString (this BinaryWriter writer, string? value)
+	{
+		writer.Write (value is not null);
+		if (value is not null) {
+			writer.Write (value);
+		}
+	}
+
+	static void WriteOptionalActivationCtor (this BinaryWriter writer, ActivationCtorData? constructor)
+	{
+		writer.Write (constructor is not null);
+		if (constructor is not null) {
+			writer.WriteTypeRef (constructor.DeclaringType);
+			writer.Write (constructor.IsOnLeafType);
+			writer.Write ((byte) constructor.Style);
+		}
+	}
+
 	static void WriteUcoMethod (this BinaryWriter writer, UcoMethodData method)
 	{
 		writer.Write (method.WrapperName);
 		writer.Write (method.CallbackMethodName);
 		writer.WriteTypeRef (method.CallbackType);
 		writer.Write (method.JniSignature);
+		writer.WriteOptionalStrings (method.CallbackParameterTypeNames);
+		writer.WriteOptionalString (method.CallbackReturnTypeName);
 		writer.WriteExportMethodDispatch (method.ExportMethodDispatch);
 	}
 
+	static void WriteOptionalStrings (this BinaryWriter writer, IReadOnlyList<string>? values)
+	{
+		writer.Write (values is not null);
+		if (values is null) {
+			return;
+		}
+		writer.Write (values.Count);
+		foreach (var value in values) {
+			writer.Write (value);
+		}
+	}
+
 	static void WriteExportMethodDispatch (this BinaryWriter writer, ExportMethodDispatchData? dispatch)
 	{
 		writer.Write (dispatch is not null);

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/TypeMapAssemblyGenerator.cs

@@ -29,7 +29,22 @@ public TypeMapAssemblyGenerator (Version systemRuntimeVersion)
 	/// </param>
 	public void Generate (IReadOnlyList<JavaPeerInfo> peers, Stream stream, string assemblyName, bool useSharedTypemapUniverse = false)
 	{
-		var model = ModelBuilder.Build (peers, assemblyName + ".dll", assemblyName);
+		var model = CreateModel (peers, assemblyName);
+		Generate (model, stream, useSharedTypemapUniverse);
+	}
+
+	internal TypeMapAssemblyData CreateModel (IReadOnlyList<JavaPeerInfo> peers, string assemblyName)
+	{
+		return ModelBuilder.Build (peers, assemblyName + ".dll", assemblyName);
+	}
+
+	internal byte [] ComputeIncrementalFingerprint (TypeMapAssemblyData model, bool useSharedTypemapUniverse)
+	{
+		return MetadataHelper.ComputeIncrementalFingerprint (model, _systemRuntimeVersion, useSharedTypemapUniverse);
+	}
+
+	internal void Generate (TypeMapAssemblyData model, Stream stream, bool useSharedTypemapUniverse)
+	{
 		var emitter = new TypeMapAssemblyEmitter (_systemRuntimeVersion);
 		emitter.Emit (model, stream, useSharedTypemapUniverse);
 	}

src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs

@@ -30,6 +30,13 @@ public TrimmableTypeMapGenerator (ITrimmableTypeMapLogger logger)
 	/// Set to <see langword="false"/> when callers do not consume method metadata for types
 	/// that cannot generate Java callable wrappers.
 	/// </param>
+	/// <param name="shouldGenerateTypeMapAssembly">
+	/// Optional incremental-build callback. It receives each output assembly name and a
+	/// content-model fingerprint, and returns whether that assembly should be emitted.
+	/// Assemblies skipped by the callback are omitted from
+	/// <see cref="TrimmableTypeMapResult.GeneratedAssemblies"/>. When omitted, all typemap
+	/// assemblies are generated.
+	/// </param>
 	public TrimmableTypeMapResult Execute (
 		IReadOnlyList<AssemblyInput> assemblies,
 		Version systemRuntimeVersion,
@@ -40,7 +47,8 @@ public TrimmableTypeMapResult Execute (
 		string? packageNamingPolicy = null,
 		bool generateTypeMapAssemblies = true,
 		bool errorOnCustomJavaObject = true,
-		bool collectMarshalMethodsForNonAcw = true)
+		bool collectMarshalMethodsForNonAcw = true,
+		Func<string, byte [], bool>? shouldGenerateTypeMapAssembly = null)
 	{
 		_ = assemblies ?? throw new ArgumentNullException (nameof (assemblies));
 		_ = systemRuntimeVersion ?? throw new ArgumentNullException (nameof (systemRuntimeVersion));
@@ -65,7 +73,7 @@ public TrimmableTypeMapResult Execute (
 		}
 
 		var generatedAssemblies = generateTypeMapAssemblies
-			? GenerateTypeMapAssemblies (allPeers, systemRuntimeVersion, useSharedTypemapUniverse)
+			? GenerateTypeMapAssemblies (allPeers, systemRuntimeVersion, useSharedTypemapUniverse, shouldGenerateTypeMapAssembly)
 			: [];
 		var jcwPeers = allPeers.Where (ShouldGenerateJcw).ToList ();
 		logger.LogGeneratingJcwFilesInfo (jcwPeers.Count, allPeers.Count);
@@ -284,10 +292,11 @@ GeneratedManifest GenerateManifest (List<JavaPeerInfo> allPeers, AssemblyManifes
 		return (peers, manifestInfo);
 	}
 
-	List<GeneratedAssembly> GenerateTypeMapAssemblies (
+	internal List<GeneratedAssembly> GenerateTypeMapAssemblies (
 		List<JavaPeerInfo> allPeers,
 		Version systemRuntimeVersion,
-		bool useSharedTypemapUniverse)
+		bool useSharedTypemapUniverse,
+		Func<string, byte [], bool>? shouldGenerateTypeMapAssembly = null)
 	{
 		List<(string AssemblyName, List<JavaPeerInfo> Peers)> peersByAssembly;
 
@@ -315,18 +324,33 @@ List<GeneratedAssembly> GenerateTypeMapAssemblies (
 		foreach (var (assemblyName, peers) in peersByAssembly) {
 			string typeMapAssemblyName = $"_{assemblyName}.TypeMap";
 			perAssemblyNames.Add (typeMapAssemblyName);
+			var model = generator.CreateModel (peers, typeMapAssemblyName);
+			if (shouldGenerateTypeMapAssembly is not null) {
+				var fingerprint = generator.ComputeIncrementalFingerprint (model, useSharedTypemapUniverse);
+				if (!shouldGenerateTypeMapAssembly (typeMapAssemblyName, fingerprint)) {
+					continue;
+				}
+			}
 			var stream = new MemoryStream ();
-			generator.Generate (peers, stream, typeMapAssemblyName, useSharedTypemapUniverse);
+			generator.Generate (model, stream, useSharedTypemapUniverse);
 			stream.Position = 0;
 			generatedAssemblies.Add (new GeneratedAssembly (typeMapAssemblyName, stream));
 			logger.LogGeneratedTypeMapAssemblyInfo (typeMapAssemblyName, peers.Count);
 		}
-		var rootStream = new MemoryStream ();
-		var rootGenerator = new RootTypeMapAssemblyGenerator (systemRuntimeVersion);
-		rootGenerator.Generate (perAssemblyNames, useSharedTypemapUniverse, rootStream);
-		rootStream.Position = 0;
-		generatedAssemblies.Add (new GeneratedAssembly ("_Microsoft.Android.TypeMaps", rootStream));
-		logger.LogGeneratedRootTypeMapInfo (perAssemblyNames.Count);
+		const string rootAssemblyName = "_Microsoft.Android.TypeMaps";
+		bool generateRoot = true;
+		if (shouldGenerateTypeMapAssembly is not null) {
+			var rootFingerprint = MetadataHelper.ComputeRootIncrementalFingerprint (perAssemblyNames, systemRuntimeVersion, useSharedTypemapUniverse);
+			generateRoot = shouldGenerateTypeMapAssembly (rootAssemblyName, rootFingerprint);
+		}
+		if (generateRoot) {
+			var rootStream = new MemoryStream ();
+			var rootGenerator = new RootTypeMapAssemblyGenerator (systemRuntimeVersion);
+			rootGenerator.Generate (perAssemblyNames, useSharedTypemapUniverse, rootStream);
+			rootStream.Position = 0;
+			generatedAssemblies.Add (new GeneratedAssembly (rootAssemblyName, rootStream));
+			logger.LogGeneratedRootTypeMapInfo (perAssemblyNames.Count);
+		}
 		logger.LogGeneratedTypeMapAssembliesInfo (generatedAssemblies.Count);
 		return generatedAssemblies;
 	}

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets

@@ -46,6 +46,7 @@
          Outputs without making the target run on every build. The stamp is always
          touched, so the target is correctly skipped when none of its Inputs changed. -->
     <_TrimmableTypeMapOutputStamp>$(_TypeMapOutputDirectory)_GenerateTrimmableTypeMap.stamp</_TrimmableTypeMapOutputStamp>
+    <_TrimmableTypeMapFingerprintsFile>$(_TypeMapOutputDirectory)typemap-fingerprints.txt</_TrimmableTypeMapFingerprintsFile>
     <_TrimmableRemoveRegisterFlag>$(_AndroidStampDirectory)_RemoveRegisterAttribute.stamp</_TrimmableRemoveRegisterFlag>
     <_TrimmableRemoveRegisterTarget Condition=" '$(_AndroidRuntime)' == 'CoreCLR' ">_RemoveRegisterAttributeCoreClr</_TrimmableRemoveRegisterTarget>
     <_TrimmableRemoveRegisterTarget Condition=" '$(_AndroidRuntime)' == 'NativeAOT' ">_RemoveRegisterAttributeNativeAot</_TrimmableRemoveRegisterTarget>
@@ -170,6 +171,7 @@
         ApplicationJavaClass="$(AndroidApplicationJavaClass)"
         ErrorOnCustomJavaObject="$(AndroidErrorOnCustomJavaObject)"
         GeneratedAssembliesListFile="$(_TypeMapAssembliesListFile)"
+        TypeMapFingerprintsFile="$(_TrimmableTypeMapFingerprintsFile)"
         AcwMapOutputFile="$(_PreTrimTypeMapAcwMapOutputFile)"
         ApplicationRegistrationOutputFile="$(_PreTrimTypeMapApplicationRegistrationOutputFile)">
       <Output TaskParameter="GeneratedAssemblies" ItemName="_GeneratedTypeMapAssemblies" />
@@ -200,6 +202,7 @@
       <FileWrites Include="@(_GeneratedTypeMapAssemblies)" />
       <FileWrites Include="@(_GeneratedJavaFiles)" />
       <FileWrites Include="$(_TypeMapAssembliesListFile)" />
+      <FileWrites Include="$(_TrimmableTypeMapFingerprintsFile)" />
       <FileWrites Include="$(_TypeMapJavaFilesList)" />
       <FileWrites Include="$(_TrimmableTypeMapOutputStamp)" />
       <FileWrites Include="$(_TypeMapBaseOutputDir)AndroidManifest.xml" />
@@ -274,6 +277,7 @@
       <FileWrites Include="$(_PostTrimTypeMapJavaFilesList)" Condition="Exists('$(_PostTrimTypeMapJavaFilesList)')" />
       <FileWrites Include="$(_PostTrimTrimmableTypeMapJavaStamp)" Condition="Exists('$(_PostTrimTrimmableTypeMapJavaStamp)')" />
       <FileWrites Include="$(_TypeMapAssembliesListFile)" />
+      <FileWrites Include="$(_TrimmableTypeMapFingerprintsFile)" Condition="Exists('$(_TrimmableTypeMapFingerprintsFile)')" />
       <FileWrites Include="$(_TypeMapJavaFilesList)" Condition="Exists('$(_TypeMapJavaFilesList)')" />
       <FileWrites Include="$(_TrimmableTypeMapOutputStamp)" Condition="Exists('$(_TrimmableTypeMapOutputStamp)')" />
       <FileWrites Include="$(_TypeMapBaseOutputDir)AndroidManifest.xml" Condition="Exists('$(_TypeMapBaseOutputDir)AndroidManifest.xml')" />