add support for xunit TypeAsserts IsType (#240)

Author: Meir017

src/FluentAssertions.Analyzers.Tests/Tips/XunitTests.cs

@@ -598,6 +598,28 @@ public void AssertIsNotAssignableFrom_TestAnalyzer(string assertion) =>
         public void AssertIsNotAssignableFrom_TestCodeFix(string oldAssertion, string newAssertion)
             => VerifyCSharpFix<AssertIsNotAssignableFromCodeFix, AssertIsNotAssignableFromAnalyzer>("string actual, Type expected", oldAssertion, newAssertion);
 
+        [DataTestMethod]
+        [DataRow("Assert.IsType(expected, actual);")]
+        [DataRow("Assert.IsType(typeof(string), actual);")]
+        [DataRow("Assert.IsType<string>(actual);")]
+        [Implemented]
+        public void AssertIsType_TestAnalyzer(string assertion) =>
+            VerifyCSharpDiagnostic<AssertIsTypeAnalyzer>("string actual, Type expected", assertion);
+
+        [DataTestMethod]
+        [DataRow(
+            /* oldAssertion: */ "Assert.IsType(expected, actual);",
+            /* newAssertion: */ "actual.Should().BeOfType(expected);")]
+        [DataRow(
+            /* oldAssertion: */ "Assert.IsType(typeof(string), actual);",
+            /* newAssertion: */ "actual.Should().BeOfType<string>();")]
+        [DataRow(
+            /* oldAssertion: */ "Assert.IsType<string>(actual);",
+            /* newAssertion: */ "actual.Should().BeOfType<string>();")]
+        [Implemented]
+        public void AssertIsType_TestCodeFix(string oldAssertion, string newAssertion)
+            => VerifyCSharpFix<AssertIsTypeCodeFix, AssertIsTypeAnalyzer>("string actual, Type expected", oldAssertion, newAssertion);
+
         private void VerifyCSharpDiagnostic<TDiagnosticAnalyzer>(string methodArguments, string assertion) where TDiagnosticAnalyzer : Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer, new()
         {
             var source = GenerateCode.XunitAssertion(methodArguments, assertion);

src/FluentAssertions.Analyzers/Constants.cs

@@ -139,6 +139,7 @@ public static class Xunit
             public const string AssertSubset = $"{DiagnosticProperties.IdPrefix}0717";
             public const string AssertIsAssignableFrom = $"{DiagnosticProperties.IdPrefix}0718";
             public const string AssertIsNotAssignableFrom = $"{DiagnosticProperties.IdPrefix}0719";
+            public const string AssertIsType = $"{DiagnosticProperties.IdPrefix}0720";
         }
     }
 

src/FluentAssertions.Analyzers/Tips/Xunit/AssertIsType.cs

@@ -0,0 +1,71 @@
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using FluentAssertions.Analyzers.Utilities;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using SF = Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
+
+namespace FluentAssertions.Analyzers.Xunit;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class AssertIsTypeAnalyzer : XunitAnalyzer
+{
+    public const string DiagnosticId = Constants.Tips.Xunit.AssertIsType;
+    public const string Category = Constants.Tips.Category;
+
+    public const string Message = "Use .Should().BeOfType().";
+
+    protected override DiagnosticDescriptor Rule => new(DiagnosticId, Title, Message, Category, DiagnosticSeverity.Info, true);
+
+    protected override IEnumerable<FluentAssertionsCSharpSyntaxVisitor> Visitors => new FluentAssertionsCSharpSyntaxVisitor[]
+    {
+        new AssertIsTypeGenericTypeSyntaxVisitor(),
+        new AssertIsTypeTypeSyntaxVisitor()
+    };
+
+    //public static T IsType<T>(object? @object)
+    public class AssertIsTypeGenericTypeSyntaxVisitor : FluentAssertionsCSharpSyntaxVisitor
+    {
+        public AssertIsTypeGenericTypeSyntaxVisitor() : base(
+            MemberValidator.HasArguments("IsType", 1)
+        )
+        {
+        }
+    }
+
+    //public static T IsType(Type expectedType, object? @object)
+    public class AssertIsTypeTypeSyntaxVisitor : FluentAssertionsCSharpSyntaxVisitor
+    {
+        public AssertIsTypeTypeSyntaxVisitor() : base(
+            MemberValidator.HasArguments("IsType", 2)
+        )
+        {
+        }
+    }
+}
+
+[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(AssertIsTypeCodeFix)), Shared]
+public class AssertIsTypeCodeFix : XunitCodeFixProvider
+{
+    public override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(AssertIsTypeAnalyzer.DiagnosticId);
+
+    protected override ExpressionSyntax GetNewExpression(
+        ExpressionSyntax expression,
+        FluentAssertionsDiagnosticProperties properties)
+    {
+        switch (properties.VisitorName)
+        {
+            case nameof(AssertIsTypeAnalyzer.AssertIsTypeGenericTypeSyntaxVisitor):
+                return RenameMethodAndReorderActualExpectedAndReplaceWithSubjectShould(expression, "IsType", "BeOfType");
+            case nameof(AssertIsTypeAnalyzer.AssertIsTypeTypeSyntaxVisitor):
+                var newExpression = RenameMethodAndReorderActualExpectedAndReplaceWithSubjectShould(expression, "IsType", "BeOfType");
+                return ReplaceTypeOfArgumentWithGenericTypeIfExists(newExpression, "BeOfType");
+            default:
+                throw new System.InvalidOperationException($"Invalid visitor name - {properties.VisitorName}");
+        }
+    }
+}