Fixes for .NET 6 linker

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -317,11 +317,55 @@
 			<!-- Mark our entry assembly as a root assembly. -->
 			<TrimmerRootAssembly Include="@(ResolvedFileToPublish)" Condition="'%(ResolvedFileToPublish.Filename)' == '$(AssemblyName)' And '%(ResolvedFileToPublish.Extension)' == '.dll'" />
 
-			<!-- add a custom step which inserts any other steps we need -->
-			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)">
-				<BeforeStep>MarkStep</BeforeStep>
-				<Type>Xamarin.SetupStep</Type>
-			</_TrimmerCustomSteps>
+			<!--
+				pre-mark custom steps
+			-->
+			<!-- TODO: reverse the pre-mark steps once we get the fix from https://github.com/mono/linker/pull/2082 -->
+			<!-- TODO: these steps should probably run after mark. -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="MarkStep" Condition="'$(_LinkMode)' != 'None'" Type="Xamarin.Linker.Steps.PreMarkDispatcher" />
+			<!-- The final decision to remove/keep the dynamic registrar must be done before the linking step -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="MarkStep" Type="MonoTouch.Tuner.RegistrarRemovalTrackingStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="MarkStep" Type="MonoTouch.Tuner.CoreTypeMapStep" />
+			<!-- Load the list of assemblies loaded by the linker. -->
+			<!-- This would not be needed if LinkContext.GetAssemblies () was exposed to us. -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="MarkStep" Type="Xamarin.Linker.CollectAssembliesStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="MarkStep" Type="Xamarin.SetupStep" />
+
+			<!--
+				IMarkHandlers which run during Mark
+			-->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" Condition="'$(_LinkMode)' != 'None'" Type="Xamarin.Linker.Steps.PreserveBlockCodeHandler" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" Condition="'$(_LinkMode)' != 'None'" Type="Xamarin.Linker.OptimizeGeneratedCodeHandler" />
+			<!-- MarkDispatcher substeps will run for all marked assemblies. -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" Condition="'$(_LinkMode)' != 'None'" Type="Xamarin.Linker.Steps.MarkDispatcher" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" Condition="'$(_LinkMode)' != 'None'" Type="Xamarin.Linker.Steps.PreserveSmartEnumConversionsHandler" />
+
+			<!--
+				post-sweep custom steps
+			-->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="SweepStep" Condition="'$(_LinkMode)' != 'None'" Type="Xamarin.Linker.Steps.PostSweepDispatcher" />
+
+			<!--
+				pre-output custom steps
+			-->
+			<!-- TODO: reverse the pre-output steps once we get the fix from https://github.com/mono/linker/pull/2082 -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="OutputStep" Type="Xamarin.Linker.Steps.PreOutputDispatcher" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="OutputStep" Type="Xamarin.Linker.ExtractBindingLibrariesStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="OutputStep" Type="Xamarin.Linker.LoadNonSkippedAssembliesStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" BeforeStep="OutputStep" Type="Xamarin.Linker.Steps.ListExportedSymbols" />
+
+			<!--
+				post-output steps
+			-->
+			<!-- TODO: remove AfterStep="OutputStep" from the post-output steps once we get the fix from https://github.com/mono/linker/pull/2082 -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.Linker.RegistrarStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.GenerateMainStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.GenerateReferencesStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.GatherFrameworksStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.Linker.ComputeNativeBuildFlagsStep" />
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.Linker.ComputeAOTArguments" />
+			<!-- Must be the last step. -->
+			<_TrimmerCustomSteps Include="$(_AdditionalTaskAssembly)" AfterStep="OutputStep" Type="Xamarin.Linker.DoneStep" />
 
 			<!-- _BundlerXmlDefinitions comes from any -xml arguments to mtouch/mmp -->
 			<TrimmerRootDescriptor Include="@(_BundlerXmlDefinitions)" />

tests/dotnet/UnitTests/ProjectTest.cs

@@ -442,14 +442,14 @@ void AssertThatLinkerExecuted (ExecutionResult result)
 		{
 			var output = BinLog.PrintToString (result.BinLogPath);
 			Assert.That (output, Does.Contain ("Building target \"_RunILLink\" completely."), "Linker did not executed as expected.");
-			Assert.That (output, Does.Contain ("Pipeline Steps:"), "Custom steps did not run as expected.");
+			Assert.That (output, Does.Contain ("LinkerConfiguration:"), "Custom steps did not run as expected.");
 		}
 
 		void AssertThatLinkerDidNotExecute (ExecutionResult result)
 		{
 			var output = BinLog.PrintToString (result.BinLogPath);
 			Assert.That (output, Does.Not.Contain ("Building target \"_RunILLink\" completely."), "Linker did not executed as expected.");
-			Assert.That (output, Does.Not.Contain ("Pipeline Steps:"), "Custom steps did not run as expected.");
+			Assert.That (output, Does.Not.Contain ("LinkerConfiguration:"), "Custom steps did not run as expected.");
 		}
 
 		void AssertAppContents (ApplePlatform platform, string app_directory)

tools/dotnet-linker/Extensions.cs

@@ -0,0 +1,32 @@
+using Mono.Cecil;
+using Mono.Linker;
+using Mono.Tuner;
+using System;
+
+namespace Xamarin.Linker {
+	public static class Extensions {
+		public static bool Inherits (this TypeReference self, string @namespace, string name, IMetadataResolver resolver)
+		{
+			if (@namespace == null)
+				throw new ArgumentNullException ("namespace");
+			if (name == null)
+				throw new ArgumentNullException ("name");
+			if (self == null)
+				return false;
+
+			TypeReference current = resolver.Resolve (self);
+			while (current != null) {
+				if (current.Is (@namespace, name))
+					return true;
+				if (current.Is ("System", "Object"))
+					return false;
+
+				TypeDefinition td = resolver.Resolve (current);
+				if (td == null)
+					return false;		// could not resolve type
+				current = td.BaseType;
+			}
+			return false;
+		}
+	}
+}

tools/dotnet-linker/SetupStep.cs

@@ -17,129 +17,12 @@ public class SetupStep : ConfigurationAwareStep {
 		protected override string Name { get; } = "Setup";
 		protected override int ErrorCode { get; } = 2300;
 
-		List<IStep> _steps;
-		public List<IStep> Steps {
-			get {
-				if (_steps == null) {
-					var pipeline = typeof (LinkContext).GetProperty ("Pipeline").GetGetMethod ().Invoke (Context, null);
-					_steps = (List<IStep>) pipeline.GetType ().GetField ("_steps", BindingFlags.Instance | BindingFlags.NonPublic).GetValue (pipeline);
-				}
-				return _steps;
-			}
-		}
-
-		List<IMarkHandler> _markHandlers;
-		List<IMarkHandler> MarkHandlers {
-			get {
-				if (_markHandlers == null) {
-					var pipeline = typeof (LinkContext).GetProperty ("Pipeline").GetGetMethod ().Invoke (Context, null);
-					_markHandlers = (List<IMarkHandler>) pipeline.GetType ().GetProperty ("MarkHandlers").GetValue (pipeline);
-				}
-				return _markHandlers;
-			}
-		}
-
-		void InsertBefore (IStep step, string stepName)
-		{
-			for (int i = 0; i < Steps.Count; i++) {
-				if (Steps [i].GetType ().Name == stepName) {
-					Steps.Insert (i, step);
-					return;
-				}
-			}
-			DumpSteps ();
-			throw new InvalidOperationException ($"Could not insert {step} before {stepName} because {stepName} wasn't found.");
-		}
-
-		void InsertAfter (IStep step, string stepName)
-		{
-			for (int i = 0; i < Steps.Count;) {
-				if (Steps [i++].GetType ().Name == stepName) {
-					Steps.Insert (i, step);
-					return;
-				}
-			}
-			DumpSteps ();
-			throw new InvalidOperationException ($"Could not insert {step} after {stepName} because {stepName} wasn't found.");
-		}
-
 		protected override void TryProcess ()
 		{
-			// Don't use --custom-step to load each step, because this assembly
-			// is loaded into the current process once per --custom-step,
-			// which makes it very difficult to share state between steps.
-
-			// Load the list of assemblies loaded by the linker.
-			// This would not be needed of LinkContext.GetAssemblies () was exposed to us.
-			InsertBefore (new CollectAssembliesStep (), "MarkStep");
-
-			// the final decision to remove/keep the dynamic registrar must be done before the linking step
-			InsertBefore (new RegistrarRemovalTrackingStep (), "MarkStep");
-
-			var pre_mark_substeps = new DotNetSubStepDispatcher ();
-			InsertBefore (pre_mark_substeps, "MarkStep");
-
-			var post_sweep_substeps = new DotNetSubStepDispatcher ();
-			InsertAfter (post_sweep_substeps, "SweepStep");
-
-			if (Configuration.LinkMode != LinkMode.None) {
-				MarkHandlers.Add (new PreserveBlockCodeHandler ());
-
-				// We need to run the ApplyPreserveAttribute step even we're only linking sdk assemblies, because even
-				// though we know that sdk assemblies will never have Preserve attributes, user assemblies may have
-				// [assembly: LinkSafe] attributes, which means we treat them as sdk assemblies and those may have
-				// Preserve attributes.
-				MarkHandlers.Add (new DotNetMarkAssemblySubStepDispatcher (new ApplyPreserveAttribute ()));
-				MarkHandlers.Add (new OptimizeGeneratedCodeHandler ());
-				MarkHandlers.Add (new DotNetMarkAssemblySubStepDispatcher (new MarkNSObjects ()));
-				MarkHandlers.Add (new PreserveSmartEnumConversionsHandler ());
-
-				// This step could be run after Mark to avoid tracking all members:
-				// https://github.com/xamarin/xamarin-macios/issues/11447
-				pre_mark_substeps.Add (new CollectUnmarkedMembersSubStep ());
-				pre_mark_substeps.Add (new StoreAttributesStep ());
-
-				post_sweep_substeps.Add (new RemoveAttributesStep ());
-			}
-
-			InsertBefore (new ListExportedSymbols (null), "OutputStep");
-			InsertBefore (new LoadNonSkippedAssembliesStep (), "OutputStep");
-			InsertBefore (new ExtractBindingLibrariesStep (), "OutputStep");
-			InsertBefore (new DotNetSubStepDispatcher (new RemoveUserResourcesSubStep ()), "OutputStep");
-			Steps.Add (new RegistrarStep ());
-			Steps.Add (new GenerateMainStep ());
-			Steps.Add (new GenerateReferencesStep ());
-			Steps.Add (new GatherFrameworksStep ());
-			Steps.Add (new ComputeNativeBuildFlagsStep ());
-			Steps.Add (new ComputeAOTArguments ());
-			Steps.Add (new DoneStep ()); // Must be the last step.
-
 			Configuration.Write ();
-
-			if (Configuration.Verbosity > 0) {
-				DumpSteps ();
-			}
-
 			ErrorHelper.Platform = Configuration.Platform;
 			Directory.CreateDirectory (Configuration.ItemsDirectory);
 			Directory.CreateDirectory (Configuration.CacheDirectory);
 		}
-
-		void DumpSteps ()
-		{
-			Console.WriteLine ();
-			Console.WriteLine ("Pipeline Steps:");
-			foreach (var step in Steps) {
-				Console.WriteLine ($"    {step}");
-				if (step is SubStepsDispatcher) {
-					var substeps = typeof (SubStepsDispatcher).GetField ("substeps", BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue (step) as IEnumerable<ISubStep>;
-					if (substeps != null) {
-						foreach (var substep in substeps) {
-							Console.WriteLine ($"        {substep}");
-						}
-					}
-				}
-			}
-		}
 	}
 }

tools/dotnet-linker/Steps/MarkDispatcher.cs

@@ -0,0 +1,14 @@
+using Mono.Linker.Steps;
+using Xamarin.Linker;
+
+namespace Xamarin.Linker.Steps {
+	class MarkDispatcher : MarkSubStepsDispatcher {
+		public MarkDispatcher ()
+			: base (new BaseSubStep[] {
+				new ApplyPreserveAttribute (),
+				new MarkNSObjects ()
+			})
+		{
+		}
+	}
+}

tools/dotnet-linker/Steps/PostSweepDispatcher.cs

@@ -0,0 +1,11 @@
+using Mono.Linker.Steps;
+using Xamarin.Linker;
+
+namespace Xamarin.Linker.Steps {
+	class PostSweepDispatcher : SubStepsDispatcher {
+		public PostSweepDispatcher ()
+			: base (new [] { new RemoveAttributesStep () })
+		{
+		}
+	}
+}

tools/dotnet-linker/Steps/PreMarkDispatcher.cs

@@ -0,0 +1,14 @@
+using Mono.Linker.Steps;
+using Xamarin.Linker;
+
+namespace Xamarin.Linker.Steps {
+	class PreMarkDispatcher : SubStepsDispatcher {
+		public PreMarkDispatcher ()
+			: base (new BaseSubStep [] {
+				new CollectUnmarkedMembersSubStep (),
+				new StoreAttributesStep ()
+				})
+		{
+		}
+	}
+}

tools/dotnet-linker/Steps/PreOutputDispatcher.cs

@@ -0,0 +1,11 @@
+using Mono.Linker.Steps;
+using Xamarin.Linker;
+
+namespace Xamarin.Linker.Steps {
+	class PreOutputDispatcher : SubStepsDispatcher {
+		public PreOutputDispatcher ()
+			: base (new [] { new RemoveUserResourcesSubStep () })
+		{
+		}
+	}
+}

tools/dotnet-linker/dotnet-linker.csproj

@@ -106,6 +106,9 @@
     <Compile Include="..\linker\CoreOptimizeGeneratedCode.cs">
       <Link>external\tools\linker\CoreOptimizeGeneratedCode.cs</Link>
     </Compile>
+    <Compile Include="..\linker\CoreTypeMapStep.cs">
+      <Link>external\tools\linker\CoreTypeMapStep.cs</Link>
+    </Compile>
     <Compile Include="..\..\src\ObjCRuntime\Registrar.cs">
       <Link>external\src\ObjCRuntime\Registrar.cs</Link>
     </Compile>

tools/linker/ApplyPreserveAttribute.cs

@@ -17,6 +17,10 @@ public class ApplyPreserveAttribute : ApplyPreserveAttributeBase {
 		HashSet<TypeDefinition> preserve_synonyms;
 #endif
 
+		// We need to run the ApplyPreserveAttribute step even if we're only linking sdk assemblies, because even
+		// though we know that sdk assemblies will never have Preserve attributes, user assemblies may have
+		// [assembly: LinkSafe] attributes, which means we treat them as sdk assemblies and those may have
+		// Preserve attributes.
 		public override bool IsActiveFor (AssemblyDefinition assembly)
 		{
 			return Annotations.GetAction (assembly) == AssemblyAction.Link;