Terminal.Gui/Terminal.Gui.Analyzers.Tests/ProjectBuilder.cs

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Text;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using System.Collections.Immutable;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Drawing;
using Microsoft.CodeAnalysis.CodeActions;
using Terminal.Gui.ViewBase;
using Terminal.Gui.Views;
using Document = Microsoft.CodeAnalysis.Document;
using Formatter = Microsoft.CodeAnalysis.Formatting.Formatter;
using System.Reflection;
using JetBrains.Annotations;

public sealed class ProjectBuilder
{
    private string? _sourceCode;
    private string? _expectedFixedCode;
    private DiagnosticAnalyzer? _analyzer;
    private CodeFixProvider? _codeFix;

    public ProjectBuilder WithSourceCode (string source)
    {
        _sourceCode = source;
        return this;
    }

    public ProjectBuilder ShouldFixCodeWith (string expected)
    {
        _expectedFixedCode = expected;
        return this;
    }

    public ProjectBuilder WithAnalyzer (DiagnosticAnalyzer analyzer)
    {
        _analyzer = analyzer;
        return this;
    }

    public ProjectBuilder WithCodeFix (CodeFixProvider codeFix)
    {
        _codeFix = codeFix;
        return this;
    }

    public async Task ValidateAsync ()
    {
        if (_sourceCode == null)
        {
            throw new InvalidOperationException ("Source code not set.");
        }

        if (_analyzer == null)
        {
            throw new InvalidOperationException ("Analyzer not set.");
        }

        // Parse original document
        Document document = CreateDocument (_sourceCode);
        Compilation? compilation = await document.Project.GetCompilationAsync ();

        ImmutableArray<Diagnostic> diagnostics = compilation!.GetDiagnostics ();
        IEnumerable<Diagnostic> errors = diagnostics.Where (d => d.Severity == DiagnosticSeverity.Error);

        IEnumerable<Diagnostic> enumerable = errors as Diagnostic [] ?? errors.ToArray ();

        if (enumerable.Any ())
        {
            string errorMessages = string.Join (Environment.NewLine, enumerable.Select (e => e.ToString ()));
            throw new Exception ("Compilation failed with errors:" + Environment.NewLine + errorMessages);
        }

        // Run analyzer
        ImmutableArray<Diagnostic> analyzerDiagnostics = await GetAnalyzerDiagnosticsAsync (compilation, _analyzer);

        Assert.NotEmpty (analyzerDiagnostics);

        if (_expectedFixedCode != null)
        {
            if (_codeFix == null)
            {
                throw new InvalidOperationException ("Expected code fix but none was set.");
            }

            Document? fixedDocument = await ApplyCodeFixAsync (document, analyzerDiagnostics.First (), _codeFix);

            if (fixedDocument is { })
            {
                Document formattedDocument = await Formatter.FormatAsync (fixedDocument);
                string fixedSource = (await formattedDocument.GetTextAsync ()).ToString ();

                Assert.Equal (_expectedFixedCode, fixedSource);
            }
        }
    }

    private static Document CreateDocument (string source)
    {
        string dd = typeof (Enumerable).GetTypeInfo ().Assembly.Location;
        DirectoryInfo coreDir = Directory.GetParent (dd) ?? throw new Exception ($"Could not find parent directory of dotnet sdk.  Sdk directory was {dd}");

        AdhocWorkspace workspace = new AdhocWorkspace ();
        ProjectId projectId = ProjectId.CreateNewId ();
        DocumentId documentId = DocumentId.CreateNewId (projectId);

        List<MetadataReference> references =
        [
            MetadataReference.CreateFromFile (typeof (Button).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (View).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (System.IO.FileSystemInfo).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (System.Linq.Enumerable).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (object).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (MarshalByValueComponent).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (ObservableCollection<string>).Assembly.Location),

            // New assemblies required by Terminal.Gui version 2
            MetadataReference.CreateFromFile (typeof (Size).Assembly.Location),
            MetadataReference.CreateFromFile (typeof (CanBeNullAttribute).Assembly.Location),


            MetadataReference.CreateFromFile (Path.Combine (coreDir.FullName, "mscorlib.dll")),
            MetadataReference.CreateFromFile (Path.Combine (coreDir.FullName, "System.Runtime.dll")),
            MetadataReference.CreateFromFile (Path.Combine (coreDir.FullName, "System.Collections.dll")),
            MetadataReference.CreateFromFile (Path.Combine (coreDir.FullName, "System.Data.Common.dll"))

            // Add more as necessary
        ];


        ProjectInfo projectInfo = ProjectInfo.Create (
                                                      projectId,
                                                      VersionStamp.Create (),
                                                      "TestProject",
                                                      "TestAssembly",
                                                      LanguageNames.CSharp,
                                                      compilationOptions: new CSharpCompilationOptions (OutputKind.DynamicallyLinkedLibrary),
                                                      metadataReferences: references);

        Solution solution = workspace.CurrentSolution
                                     .AddProject (projectInfo)
                                     .AddDocument (documentId, "Test.cs", SourceText.From (source));

        return solution.GetDocument (documentId)!;
    }

    private static async Task<ImmutableArray<Diagnostic>> GetAnalyzerDiagnosticsAsync (Compilation compilation, DiagnosticAnalyzer analyzer)
    {
        CompilationWithAnalyzers compilationWithAnalyzers = compilation.WithAnalyzers ([analyzer]);
        return await compilationWithAnalyzers.GetAnalyzerDiagnosticsAsync ();
    }

    private static async Task<Document?> ApplyCodeFixAsync (Document document, Diagnostic diagnostic, CodeFixProvider codeFix)
    {
        CodeAction? codeAction = null;
        var context = new CodeFixContext ((TextDocument)document, diagnostic, (action, _) => codeAction = action, CancellationToken.None);

        await codeFix.RegisterCodeFixesAsync (context);

        if (codeAction == null)
        {
            throw new InvalidOperationException ("Code fix did not register a fix.");
        }

        ImmutableArray<CodeActionOperation> operations = await codeAction.GetOperationsAsync (CancellationToken.None);
        Solution solution = operations.OfType<ApplyChangesOperation> ().First ().ChangedSolution;
        return solution.GetDocument (document.Id);
    }
}