xamarin-macios/tools/dotnet-linker/ApplyPreserveAttributeBase.cs

// This is copied from https://github.com/mono/linker/blob/fa9ccbdaf6907c69ef1bb117906f8f012218d57f/src/tuner/Mono.Tuner/ApplyPreserveAttributeBase.cs
// and modified to work without a Profile class.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

using Mono.Linker;
using Mono.Linker.Steps;

using Mono.Cecil;

namespace Mono.Tuner {

	public abstract class ApplyPreserveAttributeBase : BaseSubStep {

		// set 'removeAttribute' to true if you want the preserved attribute to be removed from the final assembly
		protected abstract bool IsPreservedAttribute (ICustomAttributeProvider provider, CustomAttribute attribute, out bool removeAttribute);

		public override SubStepTargets Targets {
			get {
				return SubStepTargets.Type
					| SubStepTargets.Field
					| SubStepTargets.Method
					| SubStepTargets.Property
					| SubStepTargets.Event;
			}
		}

		public override bool IsActiveFor (AssemblyDefinition assembly)
		{
			return Annotations.GetAction (assembly) == AssemblyAction.Link;
		}

		public override void ProcessType (TypeDefinition type)
		{
			TryApplyPreserveAttribute (type);
		}

		public override void ProcessField (FieldDefinition field)
		{
			foreach (var attribute in GetPreserveAttributes (field))
				Mark (field, attribute);
		}

		public override void ProcessMethod (MethodDefinition method)
		{
			MarkMethodIfPreserved (method);
		}

		public override void ProcessProperty (PropertyDefinition property)
		{
			foreach (var attribute in GetPreserveAttributes (property)) {
				MarkMethod (property.GetMethod, attribute);
				MarkMethod (property.SetMethod, attribute);
			}
		}

		public override void ProcessEvent (EventDefinition @event)
		{
			foreach (var attribute in GetPreserveAttributes (@event)) {
				MarkMethod (@event.AddMethod, attribute);
				MarkMethod (@event.InvokeMethod, attribute);
				MarkMethod (@event.RemoveMethod, attribute);
			}
		}

		void MarkMethodIfPreserved (MethodDefinition method)
		{
			foreach (var attribute in GetPreserveAttributes (method)) 
				MarkMethod (method, attribute);
		}

		void MarkMethod (MethodDefinition method, CustomAttribute preserve_attribute)
		{
			if (method == null)
				return;

			Mark (method, preserve_attribute);
			Annotations.SetAction (method, MethodAction.Parse);
		}

		void Mark (IMetadataTokenProvider provider, CustomAttribute preserve_attribute)
		{
			if (IsConditionalAttribute (preserve_attribute)) {
				PreserveConditional (provider);
				return;
			}

			PreserveUnconditional (provider);
		}

		void PreserveConditional (IMetadataTokenProvider provider)
		{
			var method = provider as MethodDefinition;
			if (method == null) {
				// workaround to support (uncommon but valid) conditional fields form [Preserve]
				PreserveUnconditional (provider);
				return;
			}

			Annotations.AddPreservedMethod (method.DeclaringType, method);
		}

		static bool IsConditionalAttribute (CustomAttribute attribute)
		{
			if (attribute == null)
				return false;

			foreach (var named_argument in attribute.Fields)
				if (named_argument.Name == "Conditional")
					return (bool) named_argument.Argument.Value;

			return false;
		}

		void PreserveUnconditional (IMetadataTokenProvider provider)
		{
			Annotations.Mark (provider);

			var member = provider as IMemberDefinition;
			if (member == null || member.DeclaringType == null)
				return;

			Mark (member.DeclaringType, null);
		}

		void TryApplyPreserveAttribute (TypeDefinition type)
		{
			foreach (var attribute in GetPreserveAttributes (type)) {
				Annotations.Mark (type);

				if (!attribute.HasFields)
					continue;
 
				foreach (var named_argument in attribute.Fields)
					if (named_argument.Name == "AllMembers" && (bool)named_argument.Argument.Value)
						Annotations.SetPreserve (type, TypePreserve.All);
			}
		}

		List<CustomAttribute> GetPreserveAttributes (ICustomAttributeProvider provider)
		{
			List<CustomAttribute> attrs = new List<CustomAttribute> ();

			if (!provider.HasCustomAttributes)
				return attrs;

			var attributes = provider.CustomAttributes;

			for (int i = attributes.Count - 1; i >= 0; i--) {
				var attribute = attributes [i];

				bool remote_attribute;
				if (!IsPreservedAttribute (provider, attribute, out remote_attribute))
					continue;

				attrs.Add (attribute);
				if (remote_attribute)
					attributes.RemoveAt (i);
			}

			return attrs;
		}
	}
}