ApiGenerator.cs

using Microsoft.CSharp;
using Mono.Cecil;
using Mono.Cecil.Rocks;
using System;
using System.CodeDom;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text.RegularExpressions;
using ICustomAttributeProvider = Mono.Cecil.ICustomAttributeProvider;
using TypeAttributes = System.Reflection.TypeAttributes;

// ReSharper disable BitwiseOperatorOnEnumWithoutFlags
namespace PublicApiGenerator
{
    public static class ApiGenerator
    {
        /// <summary>
        /// Generates a public API from the specified assembly.
        /// </summary>
        /// <param name="assembly">The assembly to generate an API from.</param>
        /// <param name="options">The options to control the API output.</param>
        /// <returns>The API output.</returns>
        public static string GeneratePublicApi(this Assembly assembly, ApiGeneratorOptions? options = null)
        {
            options ??= new ApiGeneratorOptions();

            var attributeFilter = new AttributeFilter(options.ExcludeAttributes);

            using (var assemblyResolver = new DefaultAssemblyResolver())
            {
                var assemblyPath = assembly.Location;
                assemblyResolver.AddSearchDirectory(Path.GetDirectoryName(assemblyPath));
                assemblyResolver.AddSearchDirectory(AppDomain.CurrentDomain.BaseDirectory);

                var readSymbols = File.Exists(Path.ChangeExtension(assemblyPath, ".pdb"));
                using (var asm = AssemblyDefinition.ReadAssembly(assemblyPath, new ReaderParameters(ReadingMode.Deferred)
                {
                    ReadSymbols = readSymbols,
                    AssemblyResolver = assemblyResolver
                }))
                {
                    return CreatePublicApiForAssembly(
                        asm,
                        typeDefinition => options.IncludeTypes == null || options.IncludeTypes.Any(type => type.FullName == typeDefinition.FullName && type.Assembly.FullName == typeDefinition.Module.Assembly.FullName),
                        options.IncludeAssemblyAttributes,
                        options.WhitelistedNamespacePrefixes,
                        attributeFilter);
                }
            }
        }

        /// <summary>
        /// Generates a public API from the specified types.
        /// </summary>
        /// <param name="types">The types to generate an API from.</param>
        /// <param name="options">The options to control the API output.</param>
        /// <remarks>This method assumes all the types belong to the same assembly. The assembly of the first type <code>types[0].Assembly</code> is used.</remarks>
        /// <returns>The API output.</returns>
        public static string GeneratePublicApi(this Type[] types, ApiGeneratorOptions? options = null)
        {
            if (types.Length == 0)
            {
                return string.Empty;
            }
            (options ??= new ApiGeneratorOptions()).IncludeTypes = types;
            return types[0].Assembly.GeneratePublicApi(options);
        }

        /// <summary>
        /// Generates a public API from the specified type.
        /// </summary>
        /// <param name="type">The type to generate an API from.</param>
        /// <param name="options">The options to control the API output.</param>
        /// <returns>The API output.</returns>
        public static string GeneratePublicApi(this Type type, ApiGeneratorOptions? options = null)
        {
            (options ??= new ApiGeneratorOptions()).IncludeTypes = new Type[] { type };
            return type.Assembly.GeneratePublicApi(options);
        }

        [Obsolete("Use `GeneratePublicApi(this Assembly assembly, ApiGeneratorOptions? options = null)` instead. Will be removed in the next major.")]
        public static string GeneratePublicApi(Assembly assembly, Type[]? includeTypes = null, bool shouldIncludeAssemblyAttributes = true, string[]? whitelistedNamespacePrefixes = null, string[]? excludeAttributes = null)
        {
            var options = new ApiGeneratorOptions
            {
                IncludeTypes = includeTypes,
                IncludeAssemblyAttributes = shouldIncludeAssemblyAttributes,
                ExcludeAttributes = excludeAttributes,
            };
            if (whitelistedNamespacePrefixes != null)
            {
                options.WhitelistedNamespacePrefixes = whitelistedNamespacePrefixes;
            }
            return GeneratePublicApi(assembly, options);
        }

        // TODO: Assembly references?
        // TODO: Better handle namespaces - using statements? - requires non-qualified type names
        static string CreatePublicApiForAssembly(AssemblyDefinition assembly, Func<TypeDefinition, bool> shouldIncludeType, bool shouldIncludeAssemblyAttributes, string[] whitelistedNamespacePrefixes, AttributeFilter attributeFilter)
        {
            using (var provider = new CSharpCodeProvider())
            {
                var compileUnit = new CodeCompileUnit();
                if (shouldIncludeAssemblyAttributes && assembly.HasCustomAttributes)
                {
                    PopulateCustomAttributes(assembly, compileUnit.AssemblyCustomAttributes, attributeFilter);
                }

                var publicTypes = assembly.Modules.SelectMany(m => m.GetTypes())
                    .Where(t => !t.IsNested && ShouldIncludeType(t) && shouldIncludeType(t))
                    .OrderBy(t => t.FullName, StringComparer.Ordinal);
                foreach (var publicType in publicTypes)
                {
                    var @namespace = compileUnit.Namespaces.Cast<CodeNamespace>()
                        .FirstOrDefault(n => n.Name == publicType.Namespace);
                    if (@namespace == null)
                    {
                        @namespace = new CodeNamespace(publicType.Namespace);
                        compileUnit.Namespaces.Add(@namespace);
                    }

                    using (NullableContext.Push(publicType))
                    {
                        var typeDeclaration = CreateTypeDeclaration(publicType, whitelistedNamespacePrefixes, attributeFilter);
                        @namespace.Types.Add(typeDeclaration);
                    }
                }

                using (var writer = new StringWriter())
                {
                    var cgo = new CodeGeneratorOptions
                    {
                        BracingStyle = "C",
                        BlankLinesBetweenMembers = false,
                        VerbatimOrder = false,
                        IndentString = "    "
                    };

                    provider.GenerateCodeFromCompileUnit(compileUnit, writer, cgo);
                    return CodeNormalizer.NormalizeGeneratedCode(writer);
                }
            }
        }

        static bool ShouldIncludeType(TypeDefinition t)
        {
            return (t.IsPublic || t.IsNestedPublic || t.IsNestedFamily || t.IsNestedFamilyOrAssembly) && !t.IsCompilerGenerated();
        }

        static bool ShouldIncludeMember(IMemberDefinition m, string[] whitelistedNamespacePrefixes)
        {
            return !m.IsCompilerGenerated() && !IsDotNetTypeMember(m, whitelistedNamespacePrefixes) && !(m is FieldDefinition);
        }

        static bool ShouldIncludeMember(MemberAttributes memberAttributes)
        {
            switch (memberAttributes & MemberAttributes.AccessMask)
            {
                case 0: // This represents no CodeDOM keyword being specified.
                case MemberAttributes.Private:
                case MemberAttributes.Assembly:
                case MemberAttributes.FamilyAndAssembly:
                    return false;
                default:
                    return true;
            }
        }

        static bool IsDotNetTypeMember(IMemberDefinition m, string[] whitelistedNamespacePrefixes)
        {
            if (m.DeclaringType?.FullName == null)
                return false;

            return (m.DeclaringType.FullName.StartsWith("System") || m.DeclaringType.FullName.StartsWith("Microsoft"))
                && !whitelistedNamespacePrefixes.Any(prefix => m.DeclaringType.FullName.StartsWith(prefix));
        }

        static void AddMemberToTypeDeclaration(CodeTypeDeclaration typeDeclaration,
            IMemberDefinition typeDeclarationInfo,
            IMemberDefinition memberInfo,
            AttributeFilter attributeFilter)
        {
            using (NullableContext.Push(memberInfo))
            {
                if (memberInfo is MethodDefinition methodDefinition)
                {
                    if (methodDefinition.IsConstructor)
                        AddCtorToTypeDeclaration(typeDeclaration, methodDefinition, attributeFilter);
                    else
                        AddMethodToTypeDeclaration(typeDeclaration, methodDefinition, attributeFilter);
                }
                else if (memberInfo is PropertyDefinition propertyDefinition)
                {
                    AddPropertyToTypeDeclaration(typeDeclaration, typeDeclarationInfo, propertyDefinition, attributeFilter);
                }
                else if (memberInfo is EventDefinition eventDefinition)
                {
                    AddEventToTypeDeclaration(typeDeclaration, eventDefinition, attributeFilter);
                }
                else if (memberInfo is FieldDefinition fieldDefinition)
                {
                    AddFieldToTypeDeclaration(typeDeclaration, fieldDefinition, attributeFilter);
                }
            }
        }

        static CodeTypeDeclaration CreateTypeDeclaration(TypeDefinition publicType, string[] whitelistedNamespacePrefixes, AttributeFilter attributeFilter)
        {
            if (publicType.IsDelegate())
                return CreateDelegateDeclaration(publicType, attributeFilter);

            var @static = false;
            TypeAttributes attributes = 0;
            if (publicType.IsPublic || publicType.IsNestedPublic)
                attributes |= TypeAttributes.Public;
            if (publicType.IsNestedFamily || publicType.IsNestedFamilyOrAssembly)
                attributes |= TypeAttributes.NestedFamily;
            if (publicType.IsSealed && !publicType.IsAbstract)
                attributes |= TypeAttributes.Sealed;
            else if (!publicType.IsSealed && publicType.IsAbstract && !publicType.IsInterface)
                attributes |= TypeAttributes.Abstract;
            else if (publicType.IsSealed && publicType.IsAbstract)
                @static = true;

            // Static support is a hack. CodeDOM does support it, and this isn't
            // correct C#, but it's good enough for our API outline
            var name = publicType.Name;

            var isStruct = publicType.IsValueType && !publicType.IsPrimitive && !publicType.IsEnum;

            var @readonly = isStruct && publicType.CustomAttributes.Any(a =>
                                 a.AttributeType.FullName == "System.Runtime.CompilerServices.IsReadOnlyAttribute");

            var index = name.IndexOf('`');
            if (index != -1)
                name = name.Substring(0, index);

            var declarationName = string.Empty;
            if (@readonly)
                declarationName += CodeNormalizer.ReadonlyMarker;
            if (@static)
                declarationName += CodeNormalizer.StaticMarker;

            declarationName += name;

            var declaration = new CodeTypeDeclaration(declarationName)
            {
                CustomAttributes = CreateCustomAttributes(publicType, attributeFilter),
                // TypeAttributes must be specified before the IsXXX as they manipulate TypeAttributes!
                TypeAttributes = attributes,
                IsClass = publicType.IsClass,
                IsEnum = publicType.IsEnum,
                IsInterface = publicType.IsInterface,
                IsStruct = isStruct,
            };

            if (declaration.IsInterface && publicType.BaseType != null)
                throw new NotImplementedException("Base types for interfaces needs testing");

            PopulateGenericParameters(publicType, declaration.TypeParameters, attributeFilter, parameter =>
            {
                var declaringType = publicType.DeclaringType;

                while (declaringType != null)
                {
                    if (declaringType.GenericParameters.Any(p => p.Name == parameter.Name))
                        return false; // https://github.com/ApiApprover/ApiApprover/issues/108

                    declaringType = declaringType.DeclaringType;
                }

                return true;
            });

            if (publicType.BaseType != null && ShouldOutputBaseType(publicType))
            {
                if (publicType.BaseType.FullName == "System.Enum")
                {
                    var underlyingType = publicType.GetEnumUnderlyingType();
                    if (underlyingType.FullName != "System.Int32")
                        declaration.BaseTypes.Add(underlyingType.CreateCodeTypeReference());
                }
                else
                    declaration.BaseTypes.Add(publicType.BaseType.CreateCodeTypeReference(publicType));
            }
            foreach (var @interface in publicType.Interfaces.OrderBy(i => i.InterfaceType.FullName, StringComparer.Ordinal)
                .Select(t => new { Reference = t, Definition = t.InterfaceType.Resolve() })
                .Where(t => ShouldIncludeType(t.Definition))
                .Select(t => t.Reference))
                declaration.BaseTypes.Add(@interface.InterfaceType.CreateCodeTypeReference(@interface));

            foreach (var memberInfo in publicType.GetMembers().Where(memberDefinition => ShouldIncludeMember(memberDefinition, whitelistedNamespacePrefixes)).OrderBy(m => m.Name, StringComparer.Ordinal))
                AddMemberToTypeDeclaration(declaration, publicType, memberInfo, attributeFilter);

            // Fields should be in defined order for an enum
            var fields = !publicType.IsEnum
                ? publicType.Fields.OrderBy(f => f.Name, StringComparer.Ordinal)
                : (IEnumerable<FieldDefinition>)publicType.Fields;
            foreach (var field in fields)
                AddMemberToTypeDeclaration(declaration, publicType, field, attributeFilter);

            foreach (var nestedType in publicType.NestedTypes.Where(ShouldIncludeType).OrderBy(t => t.FullName, StringComparer.Ordinal))
            {
                using (NullableContext.Push(nestedType))
                {
                    var nestedTypeDeclaration = CreateTypeDeclaration(nestedType, whitelistedNamespacePrefixes, attributeFilter);
                    declaration.Members.Add(nestedTypeDeclaration);
                }
            }

            return declaration;
        }

        static CodeTypeDeclaration CreateDelegateDeclaration(TypeDefinition publicType, AttributeFilter attributeFilter)
        {
            var invokeMethod = publicType.Methods.Single(m => m.Name == "Invoke");
            using (NullableContext.Push(invokeMethod)) // for delegates NullableContextAttribute is stored on Invoke method
            {
                var name = publicType.Name;
                var index = name.IndexOf('`');
                if (index != -1)
                    name = name.Substring(0, index);
                var declaration = new CodeTypeDelegate(name)
                {
                    Attributes = MemberAttributes.Public,
                    CustomAttributes = CreateCustomAttributes(publicType, attributeFilter),
                    ReturnType = invokeMethod.ReturnType.CreateCodeTypeReference(invokeMethod.MethodReturnType),
                };

                // CodeDOM. No support. Return type attributes.
                PopulateCustomAttributes(invokeMethod.MethodReturnType, declaration.CustomAttributes, type => type.MakeReturn(), attributeFilter);
                PopulateGenericParameters(publicType, declaration.TypeParameters, attributeFilter, _ => true);
                PopulateMethodParameters(invokeMethod, declaration.Parameters, attributeFilter);

                // Of course, CodeDOM doesn't support generic type parameters for delegates. Of course.
                if (declaration.TypeParameters.Count > 0)
                {
                    var parameterNames = from parameterType in declaration.TypeParameters.Cast<CodeTypeParameter>()
                                         select parameterType.Name;
                    declaration.Name = string.Format(CultureInfo.InvariantCulture, "{0}<{1}>", declaration.Name, string.Join(", ", parameterNames));
                }

                return declaration;
            }
        }

        static bool ShouldOutputBaseType(TypeDefinition publicType)
        {
            return publicType.BaseType.FullName != "System.Object" && publicType.BaseType.FullName != "System.ValueType";
        }

        static void PopulateGenericParameters(IGenericParameterProvider publicType, CodeTypeParameterCollection parameters, AttributeFilter attributeFilter, Func<GenericParameter, bool> shouldUseParameter)
        {
            foreach (var parameter in publicType.GenericParameters.Where(shouldUseParameter))
            {
                // A little hacky. Means we get "in" and "out" prefixed on any constraints, but it's either that
                // or add it as a custom attribute
                var name = parameter.Name;
                if (parameter.IsCovariant)
                    name = "out " + name;
                if (parameter.IsContravariant)
                    name = "in " + name;

                var attributeCollection = new CodeAttributeDeclarationCollection();
                if (parameter.HasCustomAttributes)
                {
                    PopulateCustomAttributes(parameter, attributeCollection, attributeFilter);
                }

                var typeParameter = new CodeTypeParameter(name)
                {
                    HasConstructorConstraint =
                        parameter.HasDefaultConstructorConstraint && !parameter.HasNotNullableValueTypeConstraint
                };

                typeParameter.CustomAttributes.AddRange(attributeCollection.OfType<CodeAttributeDeclaration>().ToArray());

                var nullableConstraint = parameter.GetNullabilityMap().First();
                var unmanagedConstraint = parameter.CustomAttributes.Any(attr => attr.AttributeType.FullName == "System.Runtime.CompilerServices.IsUnmanagedAttribute");

                if (parameter.HasNotNullableValueTypeConstraint)
                    typeParameter.Constraints.Add(unmanagedConstraint ? " unmanaged" : " struct");

                if (parameter.HasReferenceTypeConstraint)
                    typeParameter.Constraints.Add(nullableConstraint == true ? " class?" : " class");
                else if (nullableConstraint == false)
                    typeParameter.Constraints.Add(" notnull");

                using (NullableContext.Push(parameter))
                {
                    foreach (var constraint in parameter.Constraints.Where(constraint => !IsSpecialConstraint(constraint)))
                    {
                        // for generic constraints like IEnumerable<T> call to GetElementType() returns TypeReference with Name = !0
                        var typeReference = constraint.ConstraintType /*.GetElementType()*/.CreateCodeTypeReference(constraint);
                        typeParameter.Constraints.Add(typeReference);
                    }
                }
                parameters.Add(typeParameter);
            }

            bool IsSpecialConstraint(GenericParameterConstraint constraint)
            {
                // struct
                if (constraint.ConstraintType is TypeReference reference && reference.FullName == "System.ValueType")
                    return true;

                // unmanaged
                if (constraint.ConstraintType.IsUnmanaged())
                    return true;

                return false;
            }
        }

        static CodeAttributeDeclarationCollection CreateCustomAttributes(ICustomAttributeProvider type,
            AttributeFilter attributeFilter)
        {
            var attributes = new CodeAttributeDeclarationCollection();
            PopulateCustomAttributes(type, attributes, attributeFilter);
            return attributes;
        }

        static void PopulateCustomAttributes(ICustomAttributeProvider type,
            CodeAttributeDeclarationCollection attributes,
            AttributeFilter attributeFilter)
        {
            PopulateCustomAttributes(type, attributes, ctr => ctr, attributeFilter);
        }

        static void PopulateCustomAttributes(ICustomAttributeProvider type,
            CodeAttributeDeclarationCollection attributes,
            Func<CodeTypeReference, CodeTypeReference> codeTypeModifier,
            AttributeFilter attributeFilter)
        {
            foreach (var customAttribute in type.CustomAttributes.Where(attributeFilter.ShouldIncludeAttribute).OrderBy(a => a.AttributeType.FullName, StringComparer.Ordinal).ThenBy(a => ConvertAttributeToCode(codeTypeModifier, a), StringComparer.Ordinal))
            {
                var attribute = GenerateCodeAttributeDeclaration(codeTypeModifier, customAttribute);
                attributes.Add(attribute);
            }
        }

        static CodeAttributeDeclaration GenerateCodeAttributeDeclaration(Func<CodeTypeReference, CodeTypeReference> codeTypeModifier, CustomAttribute customAttribute)
        {
            var attribute = new CodeAttributeDeclaration(codeTypeModifier(customAttribute.AttributeType.CreateCodeTypeReference(mode: NullableMode.Disable)));
            attribute.Name = AttributeNameBuilder.Get(attribute.Name);
            foreach (var arg in customAttribute.ConstructorArguments)
            {
                attribute.Arguments.Add(new CodeAttributeArgument(CreateInitialiserExpression(arg)));
            }
            foreach (var field in customAttribute.Fields.OrderBy(f => f.Name, StringComparer.Ordinal))
            {
                attribute.Arguments.Add(new CodeAttributeArgument(field.Name, CreateInitialiserExpression(field.Argument)));
            }
            foreach (var property in customAttribute.Properties.OrderBy(p => p.Name, StringComparer.Ordinal))
            {
                attribute.Arguments.Add(new CodeAttributeArgument(property.Name, CreateInitialiserExpression(property.Argument)));
            }
            return attribute;
        }

        // Litee: This method is used for additional sorting of custom attributes when multiple values are allowed
        static string ConvertAttributeToCode(Func<CodeTypeReference, CodeTypeReference> codeTypeModifier, CustomAttribute customAttribute)
        {
            using (var provider = new CSharpCodeProvider())
            {
                var cgo = new CodeGeneratorOptions
                {
                    BracingStyle = "C",
                    BlankLinesBetweenMembers = false,
                    VerbatimOrder = false
                };
                var attribute = GenerateCodeAttributeDeclaration(codeTypeModifier, customAttribute);
                var declaration = new CodeTypeDeclaration("DummyClass")
                {
                    CustomAttributes = new CodeAttributeDeclarationCollection(new[] { attribute }),
                };
                using (var writer = new StringWriter())
                {
                    provider.GenerateCodeFromType(declaration, writer, cgo);
                    return writer.ToString();
                }
            }
        }

        static CodeExpression CreateInitialiserExpression(CustomAttributeArgument attributeArgument)
        {
            if (attributeArgument.Value is CustomAttributeArgument customAttributeArgument)
            {
                return CreateInitialiserExpression(customAttributeArgument);
            }

            if (attributeArgument.Value is CustomAttributeArgument[] customAttributeArguments)
            {
                var initialisers = from argument in customAttributeArguments
                                   select CreateInitialiserExpression(argument);
                return new CodeArrayCreateExpression(attributeArgument.Type.CreateCodeTypeReference(), initialisers.ToArray());
            }

            var type = attributeArgument.Type.Resolve();
            var value = attributeArgument.Value;
            if (type.BaseType != null && type.BaseType.FullName == "System.Enum")
            {
                var originalValue = Convert.ToInt64(value);
                if (type.CustomAttributes.Any(a => a.AttributeType.FullName == "System.FlagsAttribute"))
                {
                    //var allFlags = from f in type.Fields
                    //    where f.Constant != null
                    //    let v = Convert.ToInt64(f.Constant)
                    //    where v == 0 || (originalValue & v) != 0
                    //    select (CodeExpression)new CodeFieldReferenceExpression(typeExpression, f.Name);
                    //return allFlags.Aggregate((current, next) => new CodeBinaryOperatorExpression(current, CodeBinaryOperatorType.BitwiseOr, next));

                    // I'd rather use the above, as it's just using the CodeDOM, but it puts
                    // brackets around each CodeBinaryOperatorExpression
                    var flags = from f in type.Fields
                                where f.Constant != null
                                let v = Convert.ToInt64(f.Constant)
                                where v == 0 || (originalValue & v) != 0
                                select type.FullName + "." + f.Name;
                    return new CodeSnippetExpression(flags.Aggregate((current, next) => current + " | " + next));
                }

                var allFlags = from f in type.Fields
                               where f.Constant != null
                               let v = Convert.ToInt64(f.Constant)
                               where v == originalValue
                               select new CodeFieldReferenceExpression(new CodeTypeReferenceExpression(type.CreateCodeTypeReference()), f.Name);
                return allFlags.FirstOrDefault();
            }

            if (type.FullName == "System.Type" && value is TypeReference typeRef)
            {
                return new CodeTypeOfExpression(typeRef.CreateCodeTypeReference());
            }

            if (value is string)
            {
                // CodeDOM outputs a verbatim string. Any string with \n is treated as such, so normalize
                // it to make it easier for comparisons
                value = Regex.Replace((string)value, @"\n", "\\n");
                value = Regex.Replace((string)value, @"\r\n|\r\\n", "\\r\\n");
            }

            return new CodePrimitiveExpression(value);
        }

        static void AddCtorToTypeDeclaration(CodeTypeDeclaration typeDeclaration, MethodDefinition member, AttributeFilter attributeFilter)
        {
            var attributes = member.GetMethodAttributes();
            if (!ShouldIncludeMember(attributes))
                return;

            var method = new CodeConstructor
            {
                CustomAttributes = CreateCustomAttributes(member, attributeFilter),
                Name = member.Name,
                Attributes = attributes
            };
            PopulateMethodParameters(member, method.Parameters, attributeFilter);

            typeDeclaration.Members.Add(method);
        }

        static void AddMethodToTypeDeclaration(CodeTypeDeclaration typeDeclaration, MethodDefinition member, AttributeFilter attributeFilter)
        {
            var attributes = member.GetMethodAttributes();
            if (!ShouldIncludeMember(attributes))
                return;

            if (member.IsSpecialName && !member.Name.StartsWith("op_")) return;

            var returnType = member.ReturnType.CreateCodeTypeReference(member.MethodReturnType);

            if (member.ReturnType.IsUnsafeSignatureType() || member.Parameters.Any(p => p.ParameterType.IsUnsafeSignatureType()))
                returnType = returnType.MakeUnsafe();

            var method = new CodeMemberMethod
            {
                Name = CSharpOperatorKeyword.Get(member.Name),
                Attributes = attributes,
                CustomAttributes = CreateCustomAttributes(member, attributeFilter),
                ReturnType = returnType,
            };
            PopulateCustomAttributes(member.MethodReturnType, method.ReturnTypeCustomAttributes, attributeFilter);
            PopulateGenericParameters(member, method.TypeParameters, attributeFilter, _ => true);
            PopulateMethodParameters(member, method.Parameters, attributeFilter, member.IsExtensionMethod());

            typeDeclaration.Members.Add(method);
        }

        static void PopulateMethodParameters(IMethodSignature member,
            CodeParameterDeclarationExpressionCollection parameters,
            AttributeFilter attributeFilter,
            bool isExtension = false)
        {
            foreach (var parameter in member.Parameters)
            {
                FieldDirection direction = 0;
                if (parameter.IsOut)
                    direction |= FieldDirection.Out;
                else if (parameter.ParameterType.IsByReference)
                    direction |= FieldDirection.Ref;

                var parameterType = parameter.ParameterType;
                if (parameterType is RequiredModifierType requiredModifierType)
                {
                    parameterType = requiredModifierType.ElementType;
                }
                // order is crucial because a RequiredModifierType can be a ByReferenceType
                if (parameterType is ByReferenceType byReferenceType)
                {
                    parameterType = byReferenceType.ElementType;
                }

                var type = parameterType.CreateCodeTypeReference(parameter);

                if (isExtension)
                {
                    type = type.MakeThis();
                    isExtension = false;
                }

                // special case of ref is in
                // TODO: Move CustomAttributes.Any(a => a.AttributeType.FullName == "System.Runtime.CompilerServices.IsReadOnlyAttribute") to extension method once other PR is merged
                if (parameter.CustomAttributes.Any(a =>
                        a.AttributeType.FullName == "System.Runtime.CompilerServices.IsReadOnlyAttribute"))
                {
                    type = type.MakeIn();
                    direction = FieldDirection.In;
                }

                var name = parameter.HasConstant
                    ? string.Format(CultureInfo.InvariantCulture, "{0} = {1}", parameter.Name, FormatParameterConstant(parameter))
                    : parameter.Name;
                var expression = new CodeParameterDeclarationExpression(type, name)
                {
                    Direction = direction,
                    CustomAttributes = CreateCustomAttributes(parameter, attributeFilter)
                };
                parameters.Add(expression);
            }
        }

        static object FormatParameterConstant(ParameterDefinition parameter)
        {
            if (parameter.Constant is string)
                return string.Format(CultureInfo.InvariantCulture, "\"{0}\"", parameter.Constant);

            if (parameter.Constant != null)
                return parameter.Constant;

            return parameter.ParameterType.IsValueType ? "default" : "null";
        }

        static void AddPropertyToTypeDeclaration(CodeTypeDeclaration typeDeclaration, IMemberDefinition typeDeclarationInfo, PropertyDefinition member, AttributeFilter attributeFilter)
        {
            var getterAttributes = member.GetMethod?.GetMethodAttributes() ?? 0;
            var setterAttributes = member.SetMethod?.GetMethodAttributes() ?? 0;

            var hasGet = ShouldIncludeMember(getterAttributes);
            var hasSet = ShouldIncludeMember(setterAttributes);

            if (!(hasGet | hasSet))
                return;

            var propertyAttributes = CecilEx.CombineAccessorAttributes(getterAttributes, setterAttributes);

            var propertyType = member.PropertyType.IsGenericParameter
                ? new CodeTypeReference(member.PropertyType.Name)
                : member.PropertyType.CreateCodeTypeReference(member);

            var propertyName = member.Name;
            var property = new CodeMemberProperty
            {
                Name = propertyName,
                Type = propertyType,
                Attributes = propertyAttributes,
                CustomAttributes = CreateCustomAttributes(member, attributeFilter),
                HasGet = hasGet,
                HasSet = hasSet
            };

            // DefaultMemberAttribute on type gets propagated to IndexerNameAttribute
            var defaultMemberAttribute = typeDeclarationInfo.CustomAttributes.SingleOrDefault(x =>
                x.AttributeType.FullName == "System.Reflection.DefaultMemberAttribute");
            var defaultMemberAttributeArgument = defaultMemberAttribute?.ConstructorArguments.SingleOrDefault();
            var value = defaultMemberAttributeArgument?.Value as string;
            if (!string.IsNullOrEmpty(value) && propertyName != "Item")
            {
                property.Name = "Item";
                var codeAttributeDeclaration = new CodeAttributeDeclaration(AttributeNameBuilder.Get("System.Runtime.CompilerServices.IndexerNameAttribute"));
                codeAttributeDeclaration.Arguments.Add(new CodeAttributeArgument(new CodePrimitiveExpression(value)));
                property.CustomAttributes.Add(codeAttributeDeclaration);
            }

            // Here's a nice hack, because hey, guess what, the CodeDOM doesn't support
            // attributes on getters or setters
            if (member.GetMethod != null && member.GetMethod.HasCustomAttributes)
            {
                PopulateCustomAttributes(member.GetMethod, property.CustomAttributes, type => type.MakeGet(), attributeFilter);
            }
            if (member.SetMethod != null && member.SetMethod.HasCustomAttributes)
            {
                PopulateCustomAttributes(member.SetMethod, property.CustomAttributes, type => type.MakeSet(), attributeFilter);
            }

            foreach (var parameter in member.Parameters)
            {
                property.Parameters.Add(
                    new CodeParameterDeclarationExpression(parameter.ParameterType.CreateCodeTypeReference(parameter),
                        parameter.Name));
            }

            // TODO: CodeDOM has no support for different access modifiers for getters and setters
            // TODO: CodeDOM has no support for attributes on setters or getters - promote to property?

            typeDeclaration.Members.Add(property);
        }

        static void AddEventToTypeDeclaration(CodeTypeDeclaration typeDeclaration, EventDefinition eventDefinition, AttributeFilter attributeFilter)
        {
            var addAccessorAttributes = eventDefinition.AddMethod.GetMethodAttributes();
            var removeAccessorAttributes = eventDefinition.RemoveMethod.GetMethodAttributes();

            if (!(ShouldIncludeMember(addAccessorAttributes) || ShouldIncludeMember(removeAccessorAttributes)))
                return;

            var @event = new CodeMemberEvent
            {
                Name = EventNameBuilder.AugmentEventNameWithEventModifierMarkerTemplate(eventDefinition, addAccessorAttributes, removeAccessorAttributes),
                Attributes = CecilEx.CombineAccessorAttributes(addAccessorAttributes, removeAccessorAttributes),
                CustomAttributes = CreateCustomAttributes(eventDefinition, attributeFilter),
                Type = eventDefinition.EventType.CreateCodeTypeReference(eventDefinition)
            };

            typeDeclaration.Members.Add(@event);
        }

        static void AddFieldToTypeDeclaration(CodeTypeDeclaration typeDeclaration, FieldDefinition memberInfo, AttributeFilter attributeFilter)
        {
            if (memberInfo.IsPrivate || memberInfo.IsAssembly || memberInfo.IsFamilyAndAssembly || memberInfo.IsSpecialName)
                return;

            MemberAttributes attributes = 0;
            if (memberInfo.HasConstant)
                attributes |= MemberAttributes.Const;
            if (memberInfo.IsFamily || memberInfo.IsFamilyOrAssembly)
                attributes |= MemberAttributes.Family;
            if (memberInfo.IsPublic)
                attributes |= MemberAttributes.Public;
            if (memberInfo.IsStatic && !memberInfo.HasConstant)
                attributes |= MemberAttributes.Static;

            // TODO: Values for readonly fields are set in the ctor
            var codeTypeReference = memberInfo.FieldType.CreateCodeTypeReference(memberInfo);
            if (memberInfo.IsInitOnly)
                codeTypeReference = codeTypeReference.MakeReadonly();
            if (memberInfo.FieldType.IsUnsafeSignatureType())
                codeTypeReference = codeTypeReference.MakeUnsafe();
            if (memberInfo.FieldType.IsVolatile())
                codeTypeReference = codeTypeReference.MakeVolatile();

            var field = new CodeMemberField(codeTypeReference, memberInfo.Name)
            {
                Attributes = attributes,
                CustomAttributes = CreateCustomAttributes(memberInfo, attributeFilter)
            };

            if (memberInfo.HasConstant)
                field.InitExpression = new CodePrimitiveExpression(memberInfo.Constant);

            typeDeclaration.Members.Add(field);
        }
    }
}