Turned getter-like extension methods into extension properties (#1157)

app/Tests/Analyzers/SwitchExpressionMethodAnalyzerTests.cs

@@ -0,0 +1,192 @@
+using AIStudio.Tests.Models.Generation;
+
+using SourceCodeRules.StyleAnalyzers;
+using SourceCodeRules.StyleCodeFixes;
+
+namespace AIStudio.Tests.Analyzers;
+
+/// <summary>
+/// Checks that methods and properties which only return a switch expression start it on the line of their arrow,
+/// and that the code fix of MWAIS0006 keeps everything else of the member.
+/// </summary>
+/// <remarks>
+/// Extension blocks turn many such methods into properties, so the rule has to know properties as well: a
+/// getter which does nothing but return a switch expression reads like the method it replaced.
+/// </remarks>
+[TestFixture]
+public sealed class SwitchExpressionMethodAnalyzerTests
+{
+    private const string SWITCH = "this.Kind switch { Kind.CALL => \"Call\", _ => \"Meeting\" }";
+
+    [TestCase("public string Label() { return " + SWITCH + "; }", "Method", TestName = "A method which returns a switch expression from a block")]
+    [TestCase("public string Label() =>\n" + SWITCH + ";", "Method", TestName = "A method whose switch expression starts on the next line")]
+    [TestCase("public string Label =>\n" + SWITCH + ";", "Property", TestName = "A property whose switch expression starts on the next line")]
+    [TestCase("public string Label { get { return " + SWITCH + "; } }", "Property", TestName = "A getter which returns a switch expression from a block")]
+    [TestCase("public string Label { get => " + SWITCH + "; }", "Property", TestName = "A getter with a switch expression as its body")]
+    public async Task AMemberOfAClassIsRefused(string member, string kind)
+    {
+        var reported = await CompilationHarness.AnalyzeAsync(ClassWith(member), new SwitchExpressionMethodAnalyzer());
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(reported, Has.Count.EqualTo(1));
+            Assert.That(reported.FirstOrDefault()?.Id, Is.EqualTo("MWAIS0006"));
+            Assert.That(reported.FirstOrDefault()?.GetMessage(), Does.StartWith($"{kind} with a switch expression"));
+        }
+    }
+
+    [TestCase("public string Label =>\nkind switch { Kind.CALL => \"Call\", _ => \"Meeting\" };", TestName = "An extension property whose switch expression starts on the next line")]
+    [TestCase("public string Label { get { return kind switch { Kind.CALL => \"Call\", _ => \"Meeting\" }; } }", TestName = "The getter of an extension property which returns a switch expression from a block")]
+    [TestCase("public string Label() { return kind switch { Kind.CALL => \"Call\", _ => \"Meeting\" }; }", TestName = "An extension method which returns a switch expression from a block")]
+    public async Task AMemberOfAnExtensionBlockIsRefused(string member)
+    {
+        var reported = await CompilationHarness.AnalyzeAsync(ExtensionBlockWith(member), new SwitchExpressionMethodAnalyzer());
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(reported, Has.Count.EqualTo(1));
+            Assert.That(reported.FirstOrDefault()?.Id, Is.EqualTo("MWAIS0006"));
+        }
+    }
+
+    [TestCase("public string Label() => " + SWITCH + ";", TestName = "A method with the switch expression on the line of its arrow")]
+    [TestCase("public string Label => " + SWITCH + ";", TestName = "A property with the switch expression on the line of its arrow")]
+    [TestCase("public string Label { get { return " + SWITCH + "; } set { } }", TestName = "A property with a getter and a setter")]
+    [TestCase("public string Label { get { var kind = this.Kind; return kind switch { Kind.CALL => \"Call\", _ => \"Meeting\" }; } }", TestName = "A getter which does more than return a switch expression")]
+    [TestCase("public string Label() { return \"Meeting\"; }", TestName = "A method which returns no switch expression")]
+    public async Task AnythingElseIsLeftAlone(string member)
+    {
+        var reported = await CompilationHarness.AnalyzeAsync(ClassWith(member), new SwitchExpressionMethodAnalyzer());
+
+        Assert.That(reported, Is.Empty);
+    }
+
+    [Test]
+    public async Task TheCodeFixKeepsTheAttributesTypeParametersAndConstraintsOfAMethod()
+    {
+        var source = ClassWith(
+            """
+                /// <summary>Names the hash of a value.</summary>
+                [System.Diagnostics.Contracts.Pure]
+                public static string Label<T>(T value) where T : struct
+                {
+                    return value.GetHashCode() switch
+                    {
+                        0 => "Zero",
+                        _ => "Other",
+                    };
+                }
+            """);
+
+        var expected = ClassWith(
+            """
+                /// <summary>Names the hash of a value.</summary>
+                [System.Diagnostics.Contracts.Pure]
+                public static string Label<T>(T value) where T : struct => value.GetHashCode() switch
+                {
+                    0 => "Zero",
+                    _ => "Other",
+                };
+            """);
+
+        var fixedSource = await CompilationHarness.FixAsync(source, new SwitchExpressionMethodAnalyzer(), new SwitchExpressionMethodCodeFixProvider());
+
+        Assert.That(fixedSource.ReplaceLineEndings("\n"), Is.EqualTo(expected.ReplaceLineEndings("\n")));
+    }
+
+    [Test]
+    public async Task TheCodeFixTurnsAGetterIntoAnExpressionBody()
+    {
+        var source = ClassWith(
+            """
+                public string Label
+                {
+                    get
+                    {
+                        return this.Kind switch
+                        {
+                            Kind.CALL => "Call",
+                            _ => "Meeting",
+                        };
+                    }
+                }
+            """);
+
+        var expected = ClassWith(
+            """
+                public string Label => this.Kind switch
+                {
+                    Kind.CALL => "Call",
+                    _ => "Meeting",
+                };
+            """);
+
+        var fixedSource = await CompilationHarness.FixAsync(source, new SwitchExpressionMethodAnalyzer(), new SwitchExpressionMethodCodeFixProvider());
+
+        Assert.That(fixedSource.ReplaceLineEndings("\n"), Is.EqualTo(expected.ReplaceLineEndings("\n")));
+    }
+
+    [Test]
+    public async Task TheCodeFixMovesTheSwitchOfAnExtensionPropertyOntoTheLineOfItsArrow()
+    {
+        var source = ExtensionBlockWith(
+            """
+                    public string Label =>
+                        kind switch
+                        {
+                            Kind.CALL => "Call",
+                            _ => "Meeting",
+                        };
+            """);
+
+        var expected = ExtensionBlockWith(
+            """
+                    public string Label => kind switch
+                    {
+                        Kind.CALL => "Call",
+                        _ => "Meeting",
+                    };
+            """);
+
+        var fixedSource = await CompilationHarness.FixAsync(source, new SwitchExpressionMethodAnalyzer(), new SwitchExpressionMethodCodeFixProvider());
+
+        Assert.That(fixedSource.ReplaceLineEndings("\n"), Is.EqualTo(expected.ReplaceLineEndings("\n")));
+    }
+
+    private static string ClassWith(string members) =>
+        $$"""
+          namespace Sample;
+
+          public enum Kind
+          {
+              CALL,
+              MEETING,
+          }
+
+          public sealed class Meeting
+          {
+              public Kind Kind { get; set; } = Kind.MEETING;
+
+          {{members}}
+          }
+          """;
+
+    private static string ExtensionBlockWith(string members) =>
+        $$"""
+          namespace Sample;
+
+          public enum Kind
+          {
+              CALL,
+              MEETING,
+          }
+
+          public static class KindExtensions
+          {
+              extension(Kind kind)
+              {
+          {{members}}
+              }
+          }
+          """;
+}