BindablePropertyReferenceExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml;

using Mono.Cecil;

using Xamarin.Forms.Xaml;

namespace Xamarin.Forms.Build.Tasks
{
	static class BindablePropertyReferenceExtensions
	{
		public static TypeReference GetBindablePropertyType(this FieldReference bpRef, IXmlLineInfo iXmlLineInfo, ModuleDefinition module)
		{
			if (!bpRef.Name.EndsWith("Property", StringComparison.InvariantCulture))
				throw new XamlParseException($"The name of the bindable property {bpRef.Name} does not ends with \"Property\". This is the kind of convention the world is build upon, a bit like Planck's constant.", iXmlLineInfo);
			var bpName = bpRef.Name.Substring(0, bpRef.Name.Length - 8);
			var owner = bpRef.DeclaringType;
			TypeReference declaringTypeRef = null;

			var getter = owner.GetProperty(pd => pd.Name == bpName, out declaringTypeRef)?.GetMethod;
			if (getter == null || getter.IsStatic || !getter.IsPublic)
				getter = null;
			getter = getter ?? owner.GetMethods(md => md.Name == $"Get{bpName}" &&
												md.IsStatic &&
												md.IsPublic &&
												md.Parameters.Count == 1 &&
												md.Parameters[0].ParameterType.InheritsFromOrImplements(module.ImportReference(("Xamarin.Forms.Core", "Xamarin.Forms", "BindableObject"))), module).SingleOrDefault()?.Item1;
			if (getter == null)
				throw new XamlParseException($"Missing a public static Get{bpName} or a public instance property getter for the attached property \"{bpRef.DeclaringType}.{bpRef.Name}\"", iXmlLineInfo);
			return getter.ResolveGenericReturnType(declaringTypeRef, module);
		}

		public static TypeReference GetBindablePropertyTypeConverter(this FieldReference bpRef, ModuleDefinition module)
		{
			var owner = bpRef.DeclaringType;
			var bpName = bpRef.Name.EndsWith("Property", StringComparison.Ordinal) ? bpRef.Name.Substring(0, bpRef.Name.Length - 8) : bpRef.Name;
			var property = owner.GetProperty(pd => pd.Name == bpName, out TypeReference propertyDeclaringType);
			var propertyType = property?.PropertyType?.ResolveGenericParameters(propertyDeclaringType);
			var staticGetter = owner.GetMethods(md => md.Name == $"Get{bpName}" &&
												md.IsStatic &&
												md.IsPublic &&
												md.Parameters.Count == 1 &&
												md.Parameters[0].ParameterType.InheritsFromOrImplements(module.ImportReference(("Xamarin.Forms.Core", "Xamarin.Forms", "BindableObject"))), module).SingleOrDefault()?.Item1;

			var attributes = new List<CustomAttribute>();
			if (property != null && property.HasCustomAttributes)
				attributes.AddRange(property.CustomAttributes);
			if (propertyType != null && propertyType.ResolveCached().HasCustomAttributes)
				attributes.AddRange(propertyType.ResolveCached().CustomAttributes);
			if (staticGetter != null && staticGetter.HasCustomAttributes)
				attributes.AddRange(staticGetter.CustomAttributes);
			if (staticGetter != null && staticGetter.ReturnType.ResolveGenericParameters(bpRef.DeclaringType).ResolveCached().HasCustomAttributes)
				attributes.AddRange(staticGetter.ReturnType.ResolveGenericParameters(bpRef.DeclaringType).ResolveCached().CustomAttributes);

			return attributes.FirstOrDefault(cad => TypeConverterAttribute.TypeConvertersType.Contains(cad.AttributeType.FullName))?.ConstructorArguments [0].Value as TypeReference;
		}
	}
}