Implement FileInfoCodeFix

Author: inyutin-maxim

System.IO.Abstractions.Analyzers.Tests/CodeFixes/FileInfoCodeFixTests.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using System.IO.Abstractions.Analyzers.Analyzers.FileSystemTypeAnalyzers;
+using System.IO.Abstractions.Analyzers.CodeFixes;
+using Microsoft.CodeAnalysis;
+using Roslyn.Testing.CodeFix;
+using Xunit;
+
+namespace System.IO.Abstractions.Analyzers.Tests.CodeFixes
+{
+	public class FileInfoCodeFixTests :
+		CSharpCodeFixProviderTest<FileInfoAnalyzer, FileInfoCodeFix>
+	{
+		[Theory]
+		[InlineData("BeforeFix.txt", "AfterFix.txt")]
+		public void CodeFix(string sourceBefore, string sourceAfter)
+		{
+			var sourceBeforeFix = ReadFile(sourceBefore);
+			var sourceAfterFix = ReadFile(sourceAfter);
+			VerifyFix(sourceBeforeFix, sourceAfterFix, 0, true);
+		}
+
+		protected override IEnumerable<MetadataReference> GetAdditionalReferences() => new[]
+		{
+			MetadataReference.CreateFromFile(typeof(IFileSystem).Assembly.Location)
+		};
+	}
+}

System.IO.Abstractions.Analyzers.Tests/TestData/CodeFix/FileInfoCodeFix/AfterFix.txt

@@ -0,0 +1,21 @@
+using System.IO.Abstractions;
+
+namespace SomeNameSpace
+{
+	public class WithOutFileSystem
+	{
+		private readonly IFileSystem _fileSystem;
+
+		public WithOutFileSystem(IFileSystem fileSystem)
+		{
+			_fileSystem = fileSystem;
+		}
+
+		public void SomeMethod()
+		{
+			const string filePath = "C:\\temp.txt";
+
+			FileInfo fileInf = _fileSystem.FileInfo.FromFileName(filePath);
+		}
+	}
+}

System.IO.Abstractions.Analyzers.Tests/TestData/CodeFix/FileInfoCodeFix/BeforeFix.txt

@@ -0,0 +1,21 @@
+using System.IO.Abstractions;
+
+namespace SomeNameSpace
+{
+	public class WithOutFileSystem
+	{
+		private readonly IFileSystem _fileSystem;
+
+		public WithOutFileSystem(IFileSystem fileSystem)
+		{
+			_fileSystem = fileSystem;
+		}
+
+		public void SomeMethod()
+		{
+			const string filePath = "C:\\temp.txt";
+
+			FileInfo fileInf = new FileInfo(filePath);
+		}
+	}
+}

System.IO.Abstractions.Analyzers/Analyzers/FileSystemTypeAnalyzers/FileInfoAnalyzer.cs

@@ -13,7 +13,7 @@ public class FileInfoAnalyzer : BaseFileSystemNodeAnalyzer
 		/// Diagnostic Identifier
 		/// </summary>
 		[UsedImplicitly]
-		public const string DiagnosticId = "IO0004";
+		public const string DiagnosticId = Constants.Io0004;
 
 		/// <summary>
 		/// Diagnostic Title

System.IO.Abstractions.Analyzers/CodeActions/FileInfoCodeAction.cs

@@ -0,0 +1,44 @@
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Editing;
+using SF = Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
+
+namespace System.IO.Abstractions.Analyzers.CodeActions
+{
+	public class FileInfoCodeAction : CodeAction
+	{
+		private readonly Document _document;
+
+		private readonly ObjectCreationExpressionSyntax _creationExpressionSyntax;
+
+		private readonly FieldDeclarationSyntax _field;
+
+		public override string Title { get; }
+
+		public override string EquivalenceKey => Title;
+
+		public FileInfoCodeAction(string title, Document document, ObjectCreationExpressionSyntax creationExpressionSyntax,
+										FieldDeclarationSyntax field)
+		{
+			Title = title;
+			_document = document;
+			_creationExpressionSyntax = creationExpressionSyntax;
+			_field = field;
+		}
+
+		protected override async Task<Document> GetChangedDocumentAsync(CancellationToken cancellationToken)
+		{
+			var editor = await DocumentEditor.CreateAsync(_document, cancellationToken).ConfigureAwait(false);
+			var arguments = _creationExpressionSyntax.ArgumentList.Arguments.Select(x => x.ToFullString());
+
+			editor.ReplaceNode(_creationExpressionSyntax,
+				SF.ParseExpression($"{_field.Declaration.Variables.ToFullString()}.FileInfo.FromFileName({string.Join(",", arguments)})"));
+
+			return editor.GetChangedDocument();
+		}
+	}
+}

System.IO.Abstractions.Analyzers/CodeFixes/FileInfoCodeFix.cs

@@ -0,0 +1,48 @@
+using System.Collections.Immutable;
+using System.Composition;
+using System.IO.Abstractions.Analyzers.CodeActions;
+using System.IO.Abstractions.Analyzers.RoslynToken;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace System.IO.Abstractions.Analyzers.CodeFixes
+{
+	[Shared]
+	[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(FileInfoCodeFix))]
+	public class FileInfoCodeFix : CodeFixProvider
+	{
+		private const string Title = "Use IFileInfoFactory instead creation FileInfo for improved testablity";
+
+		public override ImmutableArray<string> FixableDiagnosticIds =>
+			ImmutableArray.Create(Constants.Io0007);
+
+		public sealed override FixAllProvider GetFixAllProvider() => WellKnownFixAllProviders.BatchFixer;
+
+		public override async Task RegisterCodeFixesAsync(CodeFixContext context)
+		{
+			var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
+			var classDeclarationSyntax = root.FindNode(context.Span).FirstAncestorOrSelf<ClassDeclarationSyntax>();
+
+			if (RoslynClassFileSystem.HasFileSystemField(classDeclarationSyntax))
+			{
+				var creationExpressionSyntax = root.FindNode(context.Span).FirstAncestorOrSelf<ObjectCreationExpressionSyntax>();
+
+				var fieldDeclarationSyntax = classDeclarationSyntax
+					.Members
+					.OfType<FieldDeclarationSyntax>()
+					.FirstOrDefault(x =>
+						x.Declaration.Type.NormalizeWhitespace().ToFullString()
+						== RoslynClassFileSystem.GetFileSystemType().ToFullString());
+
+				context.RegisterCodeFix(new FileInfoCodeAction(Title,
+						context.Document,
+						creationExpressionSyntax,
+						fieldDeclarationSyntax),
+					context.Diagnostics);
+			}
+		}
+	}
+}