private async Task VerifyFixInternalAsync(string language, ImmutableArray<DiagnosticAnalyzer> analyzers, CodeFixProvider codeFixProvider, string oldSource, string newSource, int? codeFixIndex,
            bool allowNewCompilerDiagnostics, int maxNumberOfIterations, Func<ImmutableArray<DiagnosticAnalyzer>, CodeFixProvider, int?, CancellationToken, Document, int, Task<Document>> getFixedDocument, CancellationToken cancellationToken)
        {
            var document = this.CreateDocument(oldSource, language);
            var compilerDiagnostics = await GetCompilerDiagnosticsAsync(document, cancellationToken).ConfigureAwait(false);

            document = await getFixedDocument(analyzers, codeFixProvider, codeFixIndex, cancellationToken, document, maxNumberOfIterations).ConfigureAwait(false);

            var newCompilerDiagnostics = GetNewDiagnostics(compilerDiagnostics, await GetCompilerDiagnosticsAsync(document, cancellationToken).ConfigureAwait(false));

            // check if applying the code fix introduced any new compiler diagnostics
            if (!allowNewCompilerDiagnostics && newCompilerDiagnostics.Any())
            {
                // Format and get the compiler diagnostics again so that the locations make sense in the output
                document = await Formatter.FormatAsync(document, Formatter.Annotation, cancellationToken: cancellationToken).ConfigureAwait(false);
                newCompilerDiagnostics = GetNewDiagnostics(compilerDiagnostics, await GetCompilerDiagnosticsAsync(document, cancellationToken).ConfigureAwait(false));

                string message =
                    string.Format("Fix introduced new compiler diagnostics:\r\n{0}\r\n\r\nNew document:\r\n{1}\r\n",
                        string.Join("\r\n", newCompilerDiagnostics.Select(d => d.ToString())),
                        (await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false)).ToFullString());
                Assert.True(false, message);
            }

            // after applying all of the code fixes, compare the resulting string to the inputted one
            var actual = await GetStringFromDocumentAsync(document, cancellationToken).ConfigureAwait(false);
            Assert.Equal(newSource, actual);
        }

        private FixAllState(
            FixAllProvider fixAllProvider,
            Document document,
            Project project,
            CodeFixProvider codeFixProvider,
            FixAllScope scope,
            string codeActionEquivalenceKey,
            IEnumerable<string> diagnosticIds,
            FixAllContext.DiagnosticProvider fixAllDiagnosticProvider)
        {
            Contract.ThrowIfNull(project);
            if (diagnosticIds == null)
            {
                throw new ArgumentNullException(nameof(diagnosticIds));
            }

            if (diagnosticIds.Any(d => d == null))
            {
                throw new ArgumentException(WorkspacesResources.Supplied_diagnostic_cannot_be_null, nameof(diagnosticIds));
            }

            this.FixAllProvider = fixAllProvider;
            this.Document = document;
            this.Project = project;
            this.CodeFixProvider = codeFixProvider ?? throw new ArgumentNullException(nameof(codeFixProvider));
            this.Scope = scope;
            this.CodeActionEquivalenceKey = codeActionEquivalenceKey;
            this.DiagnosticIds = ImmutableHashSet.CreateRange(diagnosticIds);
            this.DiagnosticProvider = fixAllDiagnosticProvider ?? throw new ArgumentNullException(nameof(fixAllDiagnosticProvider));
        }

        protected void VerifyFix(string language, DiagnosticAnalyzer analyzer, CodeFixProvider codeFixProvider, string oldSource, string newSource, int? codeFixIndex, bool allowNewCompilerDiagnostics)
        {
            Document document = CreateDocument(oldSource, language);

            VerifyFix(document, analyzer, codeFixProvider, newSource, codeFixIndex, useCompilerAnalyzerDriver: true, allowNewCompilerDiagnostics: allowNewCompilerDiagnostics);
            VerifyFix(document, analyzer, codeFixProvider, newSource, codeFixIndex, useCompilerAnalyzerDriver: false, allowNewCompilerDiagnostics: allowNewCompilerDiagnostics);
        }

        internal static async Task<ImmutableList<CodeFixEquivalenceGroup>> CreateAsync(CodeFixProvider codeFixProvider, IEnumerable<Diagnostic> allDiagnostics, Solution solution)
        {
            var fixAllProvider = codeFixProvider.GetFixAllProvider();

            var relevantDiagnostics = allDiagnostics.Where(diagnostic => codeFixProvider.FixableDiagnosticIds.Contains(diagnostic.Id)).ToImmutableArray();

            if (fixAllProvider == null)
            {
                return ImmutableList.Create<CodeFixEquivalenceGroup>();
            }

            List<CodeAction> actions = new List<CodeAction>();

            foreach (var diagnostic in relevantDiagnostics)
            {
                actions.AddRange(await GetFixesAsync(solution, codeFixProvider, diagnostic).ConfigureAwait(false));
            }

            List<CodeFixEquivalenceGroup> groups = new List<CodeFixEquivalenceGroup>();

            foreach (var item in actions.GroupBy(x => x.EquivalenceKey))
            {
                groups.Add(new CodeFixEquivalenceGroup(item.Key, solution, fixAllProvider, codeFixProvider, relevantDiagnostics));
            }

            return groups.ToImmutableList();
        }

        internal void VerifyFix(CodeFixProvider codeFixProvider,
                                DiagnosticAnalyzer diagnosticAnalyzer,
                                string language,
                                string oldSource,
                                string newSource,
                                int? codeFixIndex = null,
                                string[] allowedNewCompilerDiagnosticsId = null)
        {
            CodeFixProvider = codeFixProvider;
            DiagnosticAnalyzer = diagnosticAnalyzer;

            if (allowedNewCompilerDiagnosticsId == null || !allowedNewCompilerDiagnosticsId.Any())
            {
                VerifyFix(language, DiagnosticAnalyzer, CodeFixProvider, oldSource, newSource, codeFixIndex, false);
            }
            else
            {
                var document = DiagnosticVerifier.CreateDocument(oldSource, language);
                var compilerDiagnostics = GetCompilerDiagnostics(document).ToArray();

                VerifyFix(language, DiagnosticAnalyzer, CodeFixProvider, oldSource, newSource, codeFixIndex, true);

                var newCompilerDiagnostics = GetNewDiagnostics(compilerDiagnostics, GetCompilerDiagnostics(document)).ToList();

                if (newCompilerDiagnostics.Any(diagnostic => allowedNewCompilerDiagnosticsId.Any(s => s == diagnostic.Id)))
                {
                    Assert.AreEqual(document.GetSyntaxRootAsync().Result.ToFullString(),
                        string.Join(Environment.NewLine, newCompilerDiagnostics.Select(d => d.ToString())),
                        "Fix introduced new compiler diagnostics");
                }
            }
        }

        /// <summary>
        /// General verifier for codefixes.
        /// Creates a Document from the source string, then gets diagnostics on it and applies the relevant codefixes.
        /// Then gets the string after the codefix is applied and compares it with the expected result.
        /// Note: If any codefix causes new diagnostics to show up, the test fails unless allowNewCompilerDiagnostics is set to true.
        /// </summary>
        /// <param name="language">The language the source code is in</param>
        /// <param name="analyzer">The analyzer to be applied to the source code</param>
        /// <param name="codeFixProvider">The codefix to be applied to the code wherever the relevant Diagnostic is found</param>
        /// <param name="oldSource">A class in the form of a string before the CodeFix was applied to it</param>
        /// <param name="newSource">A class in the form of a string after the CodeFix was applied to it</param>
        /// <param name="codeFixIndex">Index determining which codefix to apply if there are multiple</param>
        /// <param name="allowNewCompilerDiagnostics">A bool controlling whether or not the test will fail if the CodeFix introduces other warnings after being applied</param>
        private void VerifyFix(string language, DiagnosticAnalyzer analyzer, CodeFixProvider codeFixProvider, string oldSource, string newSource, int? codeFixIndex, bool allowNewCompilerDiagnostics)
        {
            Document document = DiagnosticVerifier.CreateDocument(oldSource, language);
              Diagnostic[] analyzerDiagnostics = DiagnosticVerifier.GetSortedDiagnosticsFromDocuments(analyzer, new[]
                                                                                                          {
                                                                                                            document
                                                                                                          });
              IEnumerable<Diagnostic> compilerDiagnostics = CodeFixVerifier.GetCompilerDiagnostics(document);
              int attempts = analyzerDiagnostics.Length;

              for (int i = 0; i < attempts; ++i)
              {
            List<CodeAction> actions = new List<CodeAction>();
            CodeFixContext context = new CodeFixContext(document, analyzerDiagnostics[0], (a, d) => actions.Add(a), CancellationToken.None);
            codeFixProvider.RegisterCodeFixesAsync(context).Wait();

            if (!actions.Any())
            {
              break;
            }

            if (codeFixIndex != null)
            {
              document = CodeFixVerifier.ApplyFix(document, actions.ElementAt((int)codeFixIndex));
              break;
            }

            document = CodeFixVerifier.ApplyFix(document, actions.ElementAt(0));
            analyzerDiagnostics = DiagnosticVerifier.GetSortedDiagnosticsFromDocuments(analyzer, new[]
                                                                                               {
                                                                                                 document
                                                                                               });

            IEnumerable<Diagnostic> newCompilerDiagnostics = CodeFixVerifier.GetNewDiagnostics(compilerDiagnostics, CodeFixVerifier.GetCompilerDiagnostics(document));

            // check if applying the code fix introduced any new compiler diagnostics
            if (!allowNewCompilerDiagnostics && newCompilerDiagnostics.Any())
            {
              // Format and get the compiler diagnostics again so that the locations make sense in the output
              document = document.WithSyntaxRoot(Formatter.Format(document.GetSyntaxRootAsync().Result, Formatter.Annotation, document.Project.Solution.Workspace));
              newCompilerDiagnostics = CodeFixVerifier.GetNewDiagnostics(compilerDiagnostics, CodeFixVerifier.GetCompilerDiagnostics(document));

              Assert.IsTrue(false,
            string.Format("Fix introduced new compiler diagnostics:\r\n{0}\r\n\r\nNew document:\r\n{1}\r\n",
              string.Join("\r\n", newCompilerDiagnostics.Select(d => d.ToString())),
              document.GetSyntaxRootAsync().Result.ToFullString()));
            }

            // check if there are analyzer diagnostics left after the code fix
            if (!analyzerDiagnostics.Any())
            {
              break;
            }
              }

              // after applying all of the code fixes, compare the resulting string to the inputted one
              string actual = CodeFixVerifier.GetStringFromDocument(document);
              Assert.AreEqual(newSource, actual);
        }

        private static async Task<IEnumerable<CodeAction>> GetFixesAsync(Solution solution, CodeFixProvider codeFixProvider, Diagnostic diagnostic)
        {
            List<CodeAction> codeActions = new List<CodeAction>();

            await codeFixProvider.RegisterCodeFixesAsync(new CodeFixContext(solution.GetDocument(diagnostic.Location.SourceTree), diagnostic, (a, d) => codeActions.Add(a), CancellationToken.None));

            return codeActions;
        }

        /// <summary>
        /// General verifier for code fixes.
        /// Creates a Document from the source string, then gets diagnostics on it and applies the relevant code fixes.
        /// Then gets the string after the code fix is applied and compares it with the expected result.
        /// Note: If any code fix causes new diagnostics to show up, the test fails unless allowNewCompilerDiagnostics is set to true.
        /// </summary>
        /// <param name="language">The language the source code is in.</param>
        /// <param name="analyzer">The analyzer to be applied to the source code.</param>
        /// <param name="codeFixProvider">The code fix to be applied to the code wherever the relevant Diagnostic is found.</param>
        /// <param name="oldSource">A class in the form of a string before the code fix was applied to it.</param>
        /// <param name="newSource">A class in the form of a string after the code fix was applied to it.</param>
        /// <param name="codeFixIndex">Index determining which code fix to apply if there are multiple.</param>
        /// <param name="allowNewCompilerDiagnostics">A boolean controlling whether or not the test will fail if the code fix introduces other warnings after being applied.</param>
        private void VerifyFix(string language, DiagnosticAnalyzer analyzer, CodeFixProvider codeFixProvider, string oldSource, string newSource, int? codeFixIndex, bool allowNewCompilerDiagnostics)
        {
            var document = CreateDocument(oldSource, language);
            var analyzerDiagnostics = GetSortedDiagnosticsFromDocuments(analyzer, new[] { document });
            var compilerDiagnostics = GetCompilerDiagnostics(document);
            var attempts = analyzerDiagnostics.Length;

            for (int i = 0; i < attempts; ++i)
            {
                var actions = new List<CodeAction>();
                var context = new CodeFixContext(document, analyzerDiagnostics[0], (a, d) => actions.Add(a), CancellationToken.None);
                codeFixProvider.RegisterCodeFixesAsync(context).Wait();

                if (!actions.Any())
                {
                    break;
                }

                if (codeFixIndex != null)
                {
                    document = ApplyFix(document, actions.ElementAt((int)codeFixIndex));
                    break;
                }

                document = ApplyFix(document, actions.ElementAt(0));
                analyzerDiagnostics = CodeFixVerifier.GetSortedDiagnosticsFromDocuments(analyzer, new[] { document });

                var newCompilerDiagnostics = GetNewDiagnostics(compilerDiagnostics, GetCompilerDiagnostics(document));

                // Check if applying the code fix introduced any new compiler diagnostics
                if (!allowNewCompilerDiagnostics && newCompilerDiagnostics.Any())
                {
                    // Format and get the compiler diagnostics again so that the locations make sense in the output
                    document = document.WithSyntaxRoot(Formatter.Format(document.GetSyntaxRootAsync().Result, Formatter.Annotation, document.Project.Solution.Workspace));
                    newCompilerDiagnostics = GetNewDiagnostics(compilerDiagnostics, GetCompilerDiagnostics(document));

                    string message =
                        FormattableString.Invariant(
                            [email protected]"Fix introduced new compiler diagnostics:
{string.Join("\r\n", newCompilerDiagnostics.Select(d => d.ToString()))}

New document:
{document.GetSyntaxRootAsync().Result.ToFullString()}
");
                    Execute.Assertion.FailWith(message);
                }

                // Check if there are analyzer diagnostics left after the code fix
                if (!analyzerDiagnostics.Any())
                {
                    break;
                }
            }

            // After applying all of the code fixes, compare the resulting string to the inputted one
            var actual = GetStringFromDocument(document);
            actual.Should().Be(newSource);
        }

 private FixMultipleContext(
     Project triggerProject,
     CodeFixProvider codeFixProvider,
     string codeActionEquivalenceKey,
     ImmutableHashSet<string> diagnosticIds,
     FixMultipleDiagnosticProvider diagnosticProvider,
     CancellationToken cancellationToken)
     : base(triggerProject, codeFixProvider, FixAllScope.Custom, codeActionEquivalenceKey, diagnosticIds, diagnosticProvider, cancellationToken)
 {
     _diagnosticProvider = diagnosticProvider;
 }

 /// <summary>
 /// Creates a new <see cref="FixMultipleContext"/>.
 /// Use this overload when applying fix multiple diagnostics with a source location.
 /// </summary>
 /// <param name="diagnosticsToFix">Specific set of diagnostics to fix. Must be a non-empty set.</param>
 /// <param name="codeFixProvider">Underlying <see cref="CodeFixes.CodeFixProvider"/> which triggered this fix all.</param>
 /// <param name="codeActionEquivalenceKey">The <see cref="CodeAction.EquivalenceKey"/> value expected of a <see cref="CodeAction"/> participating in this fix all.</param>
 /// <param name="cancellationToken">Cancellation token for fix all computation.</param>
 public static FixMultipleContext Create(
     ImmutableDictionary<Project, ImmutableArray<Diagnostic>> diagnosticsToFix,
     CodeFixProvider codeFixProvider,
     string codeActionEquivalenceKey,
     CancellationToken cancellationToken)
 {
     var triggerProject = diagnosticsToFix.First().Key;
     var diagnosticIds = GetDiagnosticsIds(diagnosticsToFix.Values);
     var diagnosticProvider = new FixMultipleDiagnosticProvider(diagnosticsToFix);
     return new FixMultipleContext(triggerProject, codeFixProvider, codeActionEquivalenceKey, diagnosticIds, diagnosticProvider, cancellationToken);
 }

        private static bool IsInternalCodeFixProvider(CodeFixProvider fixer)
        {
            var exportAttributes = fixer.GetType().GetCustomAttributes(typeof(ExportCodeFixProviderAttribute), false);
            if (exportAttributes != null && exportAttributes.Length > 0)
            {
                var exportAttribute = (ExportCodeFixProviderAttribute)exportAttributes[0];
                return s_predefinedCodeFixProviderNames.Contains(exportAttribute.Name);
            }

            return false;
        }

        private static bool IsInternalCodeFixProvider(CodeFixProvider fixer)
        {
            var exportAttributes = fixer.GetType().GetTypeInfo().GetCustomAttributes(typeof(ExportCodeFixProviderAttribute), false);
            if (exportAttributes?.Any() == true)
            {
                var exportAttribute = (ExportCodeFixProviderAttribute)exportAttributes.First();
                return s_predefinedCodeFixProviderNames.Contains(exportAttribute.Name);
            }

            return false;
        }

 internal FixAllContext(
     Project project,
     CodeFixProvider codeFixProvider,
     FixAllScope scope,
     string codeActionId,
     IEnumerable<string> diagnosticIds,
     Func<Document, ImmutableHashSet<string>, CancellationToken, Task<IEnumerable<Diagnostic>>> getDocumentDiagnosticsAsync,
     Func<Project, bool, ImmutableHashSet<string>, CancellationToken, Task<IEnumerable<Diagnostic>>> getProjectDiagnosticsAsync,
     CancellationToken cancellationToken)
     : this(null, project, codeFixProvider, scope, codeActionId, diagnosticIds, getDocumentDiagnosticsAsync, getProjectDiagnosticsAsync, cancellationToken)
 {
 }

		public CodeFixProvider GetCodeFixProvider ()
		{
			if (instance == null) {
				try {
					instance = (CodeFixProvider)Activator.CreateInstance (codeFixProviderType);
				} catch (InvalidCastException) {
					LoggingService.LogError (codeFixProviderType + " can't be cast to CodeFixProvider.");
					throw;
				}
			}

			return instance;
		}

 internal static FixAllCodeActionContext Create(
     Project project,
     FixAllProviderInfo fixAllProviderInfo,
     CodeFixProvider originalFixProvider,
     IEnumerable<Diagnostic> originalFixDiagnostics,
     Func<Document, ImmutableHashSet<string>, CancellationToken, Task<IEnumerable<Diagnostic>>> getDocumentDiagnosticsAsync,
     Func<Project, bool, ImmutableHashSet<string>, CancellationToken, Task<IEnumerable<Diagnostic>>> getProjectDiagnosticsAsync,
     CancellationToken cancellationToken)
 {
     var diagnosticIds = GetFixAllDiagnosticIds(fixAllProviderInfo, originalFixDiagnostics).ToImmutableHashSet();
     var diagnosticProvider = new FixAllDiagnosticProvider(diagnosticIds, getDocumentDiagnosticsAsync, getProjectDiagnosticsAsync);
     return new FixAllCodeActionContext(project, fixAllProviderInfo, originalFixProvider, originalFixDiagnostics, diagnosticIds, diagnosticProvider, cancellationToken);
 }

 private CodeFixEquivalenceGroup(
     string equivalenceKey,
     Solution solution,
     FixAllProvider fixAllProvider,
     CodeFixProvider codeFixProvider,
     ImmutableArray<Diagnostic> diagnosticsToFix)
 {
     this.CodeFixEquivalenceKey = equivalenceKey;
     this.Solution = solution;
     this.FixAllProvider = fixAllProvider;
     this.CodeFixProvider = codeFixProvider;
     this.DiagnosticsToFix = diagnosticsToFix;
 }

 /// <summary>
 /// Called to test a VB codefix when applied on the inputted string as a source
 /// </summary>
 /// <param name="oldSource">A class in the form of a string before the CodeFix was applied to it</param>
 /// <param name="newSource">A class in the form of a string after the CodeFix was applied to it</param>
 /// <param name="codeFixIndex">Index determining which codefix to apply if there are multiple</param>
 /// <param name="allowNewCompilerDiagnostics">A bool controlling whether or not the test will fail if the CodeFix introduces other warnings after being applied</param>
 /// <param name="formatBeforeCompare">Format the code before comparing, bot the old source and the new.</param>
 /// <param name="codeFixProvider">The codefix to be applied to the code wherever the relevant Diagnostic is found</param>
 /// <param name="languageVersionVB">The VB language version.</param>
 protected async Task VerifyBasicFixAsync(string oldSource, string newSource, int? codeFixIndex = null, bool allowNewCompilerDiagnostics = false, bool formatBeforeCompare = false, CodeFixProvider codeFixProvider = null, Microsoft.CodeAnalysis.VisualBasic.LanguageVersion languageVersionVB = Microsoft.CodeAnalysis.VisualBasic.LanguageVersion.VisualBasic14)
 {
     if (formatBeforeCompare)
     {
         oldSource = await FormatSourceAsync(LanguageNames.VisualBasic, oldSource, languageVersionVB: languageVersionVB).ConfigureAwait(true);
         newSource = await FormatSourceAsync(LanguageNames.VisualBasic, newSource, languageVersionVB: languageVersionVB).ConfigureAwait(true);
     }
     codeFixProvider = codeFixProvider ?? GetCodeFixProvider();
     var diagnosticAnalyzer = GetDiagnosticAnalyzer();
     if (diagnosticAnalyzer != null)
         await VerifyFixAsync(LanguageNames.VisualBasic, diagnosticAnalyzer, codeFixProvider, oldSource, newSource, codeFixIndex, allowNewCompilerDiagnostics, LanguageVersion.CSharp6, languageVersionVB).ConfigureAwait(true);
     else
         await VerifyFixAsync(LanguageNames.VisualBasic, codeFixProvider.FixableDiagnosticIds, codeFixProvider, oldSource, newSource, codeFixIndex, allowNewCompilerDiagnostics, LanguageVersion.CSharp6, languageVersionVB).ConfigureAwait(true);
 }

 public Solution GetFix(
     ImmutableDictionary<Project, ImmutableArray<Diagnostic>> diagnosticsToFix,
     Workspace workspace,
     CodeFixProvider fixProvider,
     FixAllProvider fixAllProvider,
     string equivalenceKey,
     string waitDialogTitle,
     string waitDialogMessage,
     CancellationToken cancellationToken)
 {
     var fixMultipleContext = FixMultipleContext.Create(diagnosticsToFix, fixProvider, equivalenceKey, cancellationToken);
     var suggestedAction = GetSuggestedAction(fixMultipleContext, workspace, fixAllProvider, waitDialogTitle, waitDialogMessage, showPreviewChangesDialog: false, cancellationToken: cancellationToken);
     return suggestedAction.GetChangedSolution(cancellationToken);
 }

 private FixAllCodeActionContext(
     Project project,
     FixAllProviderInfo fixAllProviderInfo,
     CodeFixProvider originalFixProvider,
     IEnumerable<Diagnostic> originalFixDiagnostics,
     ImmutableHashSet<string> diagnosticIds,
     FixAllDiagnosticProvider diagnosticProvider,
     CancellationToken cancellationToken)
     : base(project, originalFixProvider, FixAllScope.Project, null, diagnosticIds, diagnosticProvider, cancellationToken)
 {
     _fixAllProviderInfo = fixAllProviderInfo;
     _originalFixDiagnostics = originalFixDiagnostics;
     _diagnosticProvider = diagnosticProvider;
 }

 public void ComputeAndApplyFix(
     ImmutableDictionary<Project, ImmutableArray<Diagnostic>> diagnosticsToFix,
     Workspace workspace,
     CodeFixProvider fixProvider,
     FixAllProvider fixAllProvider,
     string equivalenceKey,
     string waitDialogAndPreviewChangesTitle,
     string waitDialogMessage,
     bool showPreviewChangesDialog,
     CancellationToken cancellationToken)
 {
     var fixMultipleContext = FixMultipleContext.Create(diagnosticsToFix, fixProvider, equivalenceKey, cancellationToken);
     ComputeAndApplyFix(fixMultipleContext, workspace, fixAllProvider, waitDialogAndPreviewChangesTitle, waitDialogMessage, showPreviewChangesDialog, cancellationToken);
 }