Converter.cs

using System;
using System.Collections.Immutable;
using System.Linq;
using System.Xml;
using System.Xml.Linq;

using MSBuild.Abstractions;

namespace MSBuild.Conversion.Project
{
    public class Converter
    {
        private readonly UnconfiguredProject _project;
        private readonly BaselineProject _sdkBaselineProject;
        private readonly IProjectRootElement _projectRootElement;
        private readonly bool _noBackup;
        private readonly bool _forceRemoveCustomImports;
        private readonly ImmutableDictionary<string, Differ> _differs;

        public Converter(UnconfiguredProject project, BaselineProject sdkBaselineProject,
            IProjectRootElement projectRootElement, bool noBackup, bool forceRemoveCustomImports)
        {
            _project = project ?? throw new ArgumentNullException(nameof(project));
            _sdkBaselineProject = sdkBaselineProject;
            _projectRootElement = projectRootElement ?? throw new ArgumentNullException(nameof(projectRootElement));
            _noBackup = noBackup;
            _forceRemoveCustomImports = forceRemoveCustomImports;
            _differs = GetDiffers();
        }

        public void Convert(string outputPath)
        {
            ConvertProjectFile();
            CleanUpProjectFile(outputPath);
        }

        internal IProjectRootElement? ConvertProjectFile()
        {
            return _projectRootElement
                // Let's convert packages first, since that's what you should do manually anyways
                .ConvertAndAddPackages(_sdkBaselineProject.ProjectStyle, _sdkBaselineProject.TargetTFM, removePackagesConfig: _noBackup)

                // Now we can convert the project over
                .ChangeImportsAndAddSdkAttribute(_sdkBaselineProject, _forceRemoveCustomImports)
                .AddCsWinRTReferenceAndComponentProperty(_sdkBaselineProject)
                .UpdateOutputTypeProperty(_sdkBaselineProject)
                .RemoveDefaultedProperties(_sdkBaselineProject, _differs)
                .RemoveUnnecessaryPropertiesNotInSDKByDefault(_sdkBaselineProject.ProjectStyle)
                .AddTargetFrameworkProperty(_sdkBaselineProject, _sdkBaselineProject.TargetTFM)
                .AddGenerateAssemblyInfoAsFalse(_sdkBaselineProject.ProjectStyle)
                .AddDesktopProperties(_sdkBaselineProject)
                .AddCommonPropertiesToTopLevelPropertyGroup()
                .RemoveOrUpdateItems(_differs, _sdkBaselineProject, _sdkBaselineProject.TargetTFM)
                .AddItemRemovesForIntroducedItems(_differs)
                .RemoveUnnecessaryTargetsIfTheyExist()
                .RemoveWebExtensions(_sdkBaselineProject.ProjectStyle)
                .ModifyProjectElement();
        }

        internal ImmutableDictionary<string, Differ> GetDiffers() =>
            _project.ConfiguredProjects.Select(p => (p.Key, new Differ(p.Value, _sdkBaselineProject.Project.ConfiguredProjects[p.Key]))).ToImmutableDictionary(kvp => kvp.Key, kvp => kvp.Item2);

        private void CleanUpProjectFile(string outputPath)
        {
            var projectXml = _projectRootElement.Xml;

            // remove all use of xmlns attributes
            projectXml.Descendants().Attributes().Where(x => x.IsNamespaceDeclaration).Remove();
            foreach (var element in projectXml.Descendants())
            {
                if (element is null)
                {
                    continue;
                }

                // Appears to be a nullability bug?
                // Also the diagnostic doesn't show in the editor
                element.Name = element.Name.LocalName!;
            }

            // remove all use of ProductVersion
            // this is a property that is used by VS to detect which version of
            // Visual Studio opened this project last and is no longer needed
            projectXml.Descendants().Elements().Where(x => x.Name == "ProductVersion").Remove();
            projectXml.Descendants().Elements().Where(x => x.Name == "FileUpgradeFlags").Remove();
            projectXml.Descendants().Elements().Where(x => x.Name == "UpgradeBackupLocation").Remove();

            // Remove properties that do nothing if they are not set
            projectXml.Descendants().Elements().Where(x => x.Name == "ApplicationIcon" && string.IsNullOrEmpty(x.Value)).Remove();
            projectXml.Descendants().Elements().Where(x => x.Name == "PreBuildEvent" && string.IsNullOrEmpty(x.Value)).Remove();
            projectXml.Descendants().Elements().Where(x => x.Name == "PostBuildEvent" && string.IsNullOrEmpty(x.Value)).Remove();

            // Do not keep comments as the entire file is changing
            var readerSettings = new XmlReaderSettings()
            {
                IgnoreComments = true
            };
            projectXml = XDocument.Load(XmlReader.Create(projectXml.CreateReader(), readerSettings));

            // do not write out xml declaration header
            var writerSettings = new XmlWriterSettings
            {
                OmitXmlDeclaration = true,
                Indent = true,
            };
            using var writer = XmlWriter.Create(outputPath, writerSettings);
            projectXml.Save(writer);
        }
    }
}