Implement a code fix and unit tests for SA1116

Fixes #1228

StyleCop.Analyzers/StyleCop.Analyzers.Test/ReadabilityRules/SA1116UnitTests.cs

@@ -3,50 +3,51 @@
     using System.Collections.Generic;
     using System.Threading;
     using System.Threading.Tasks;
+    using Microsoft.CodeAnalysis.CodeFixes;
     using Microsoft.CodeAnalysis.Diagnostics;
     using StyleCop.Analyzers.ReadabilityRules;
     using TestHelper;
     using Xunit;
 
-    public class SA1116UnitTests : DiagnosticVerifier
+    public class SA1116UnitTests : CodeFixVerifier
     {
-        public static IEnumerable<object[]> GetTestDeclarations(string delimiter)
+        public static IEnumerable<object[]> GetTestDeclarations(string delimiter, string fixDelimiter)
         {
-            yield return new object[] { $"public Foo(int a,{delimiter} string s) {{ }}", 16 };
-            yield return new object[] { $"public object Bar(int a,{delimiter} string s) => null;", 23 };
-            yield return new object[] { $"public static Foo operator + (Foo a,{delimiter} Foo b) => null;", 35 };
-            yield return new object[] { $"public object this[int a,{delimiter} string s] => null;", 24 };
-            yield return new object[] { $"public delegate void Bar(int a,{delimiter} string s);", 30 };
+            yield return new object[] { $"public Foo(int a,{delimiter} string s) {{ }}", $"public Foo({fixDelimiter}int a,{delimiter} string s) {{ }}", 16 };
+            yield return new object[] { $"public object Bar(int a,{delimiter} string s) => null;", $"public object Bar({fixDelimiter}int a,{delimiter} string s) => null;", 23 };
+            yield return new object[] { $"public static Foo operator + (Foo a,{delimiter} Foo b) => null;", $"public static Foo operator + ({fixDelimiter}Foo a,{delimiter} Foo b) => null;", 35 };
+            yield return new object[] { $"public object this[int a,{delimiter} string s] => null;", $"public object this[{fixDelimiter}int a,{delimiter} string s] => null;", 24 };
+            yield return new object[] { $"public delegate void Bar(int a,{delimiter} string s);", $"public delegate void Bar({fixDelimiter}int a,{delimiter} string s);", 30 };
         }
 
-        public static IEnumerable<object[]> GetTestConstructorInitializers(string delimiter)
+        public static IEnumerable<object[]> GetTestConstructorInitializers(string delimiter, string fixDelimiter)
         {
-            yield return new object[] { $"this(42,{delimiter} \"hello\")" };
-            yield return new object[] { $"base(42,{delimiter} \"hello\")" };
+            yield return new object[] { $"this(42,{delimiter} \"hello\")", $"this({fixDelimiter}42,{delimiter} \"hello\")" };
+            yield return new object[] { $"base(42,{delimiter} \"hello\")", $"base({fixDelimiter}42,{delimiter} \"hello\")" };
         }
 
-        public static IEnumerable<object[]> GetTestExpressions(string delimiter)
+        public static IEnumerable<object[]> GetTestExpressions(string delimiter, string fixDelimiter)
         {
-            yield return new object[] { $"Bar(1,{delimiter} 2)", 13 };
-            yield return new object[] { $"System.Action<int, int> func = (int x,{delimiter} int y) => Bar(x, y)", 41 };
-            yield return new object[] { $"System.Action<int, int> func = delegate(int x,{delimiter} int y) {{ Bar(x, y); }}", 49 };
-            yield return new object[] { $"new string('a',{delimiter} 2)", 20 };
-            yield return new object[] { $"var arr = new string[2,{delimiter} 2];", 30 };
-            yield return new object[] { $"char cc = (new char[3, 3])[2,{delimiter} 2];", 36 };
-            yield return new object[] { $"char? c = (new char[3, 3])?[2,{delimiter} 2];", 37 };
-            yield return new object[] { $"long ll = this[2,{delimiter} 2];", 24 };
+            yield return new object[] { $"Bar(1,{delimiter} 2)", $"Bar({fixDelimiter}1,{delimiter} 2)", 13 };
+            yield return new object[] { $"System.Action<int, int> func = (int x,{delimiter} int y) => Bar(x, y)", $"System.Action<int, int> func = ({fixDelimiter}int x,{delimiter} int y) => Bar(x, y)", 41 };
+            yield return new object[] { $"System.Action<int, int> func = delegate(int x,{delimiter} int y) {{ Bar(x, y); }}", $"System.Action<int, int> func = delegate({fixDelimiter}int x,{delimiter} int y) {{ Bar(x, y); }}", 49 };
+            yield return new object[] { $"new string('a',{delimiter} 2)", $"new string({fixDelimiter}'a',{delimiter} 2)", 20 };
+            yield return new object[] { $"var arr = new string[2,{delimiter} 2];", $"var arr = new string[{fixDelimiter}2,{delimiter} 2];", 30 };
+            yield return new object[] { $"char cc = (new char[3, 3])[2,{delimiter} 2];", $"char cc = (new char[3, 3])[{fixDelimiter}2,{delimiter} 2];", 36 };
+            yield return new object[] { $"char? c = (new char[3, 3])?[2,{delimiter} 2];", $"char? c = (new char[3, 3])?[{fixDelimiter}2,{delimiter} 2];", 37 };
+            yield return new object[] { $"long ll = this[2,{delimiter} 2];", $"long ll = this[{fixDelimiter}2,{delimiter} 2];", 24 };
         }
 
         public static IEnumerable<object[]> ValidTestExpressions()
         {
-            yield return new object[] { $"System.Action func = () => Bar(0, 3)", 0 };
-            yield return new object[] { $"System.Action<int> func = x => Bar(x, 3)", 0 };
-            yield return new object[] { $"System.Action func = delegate {{ Bar(0, 0); }}", 0 };
+            yield return new object[] { $"System.Action func = () => Bar(0, 3)", null, 0 };
+            yield return new object[] { $"System.Action<int> func = x => Bar(x, 3)", null, 0 };
+            yield return new object[] { $"System.Action func = delegate {{ Bar(0, 0); }}", null, 0 };
         }
 
         [Theory]
-        [MemberData(nameof(GetTestDeclarations), "")]
-        public async Task TestValidDeclarationAsync(string declaration, int column)
+        [MemberData(nameof(GetTestDeclarations), "", "")]
+        public async Task TestValidDeclarationAsync(string declaration, string fixedDeclaration, int column)
         {
             var testCode = $@"
 class Foo
@@ -57,21 +58,28 @@ class Foo
         }
 
         [Theory]
-        [MemberData(nameof(GetTestDeclarations), "\r\n")]
-        public async Task TestInvalidDeclarationAsync(string declaration, int column)
+        [MemberData(nameof(GetTestDeclarations), "\r\n", "\r\n        ")]
+        public async Task TestInvalidDeclarationAsync(string declaration, string fixedDeclaration, int column)
         {
             var testCode = $@"
 class Foo
 {{
     {declaration}
+}}";
+            var fixedCode = $@"
+class Foo
+{{
+    {fixedDeclaration}
 }}";
             DiagnosticResult expected = this.CSharpDiagnostic().WithLocation(4, column);
             await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
         [Theory]
-        [MemberData(nameof(GetTestConstructorInitializers), "")]
-        public async Task TestValidConstructorInitializerAsync(string initializer)
+        [MemberData(nameof(GetTestConstructorInitializers), "", "")]
+        public async Task TestValidConstructorInitializerAsync(string initializer, string fixedInitializer)
         {
             var testCode = $@"
 class Base
@@ -98,8 +106,8 @@ public Derived(int i, string z)
         }
 
         [Theory]
-        [MemberData(nameof(GetTestConstructorInitializers), "\r\n")]
-        public async Task TestInvalidConstructorInitializerAsync(string initializer)
+        [MemberData(nameof(GetTestConstructorInitializers), "\r\n", "\r\n            ")]
+        public async Task TestInvalidConstructorInitializerAsync(string initializer, string fixedInitializer)
         {
             var testCode = $@"
 class Base
@@ -121,14 +129,37 @@ public Derived(int i, string z)
     {{
     }}
 }}";
+            var fixedCode = $@"
+class Base
+{{
+    public Base(int a, string s)
+    {{
+    }}
+}}
+
+class Derived : Base
+{{
+    public Derived()
+        : {fixedInitializer}
+    {{
+    }}
+
+    public Derived(int i, string z)
+        : base(i, z)
+    {{
+    }}
+}}";
+
             DiagnosticResult expected = this.CSharpDiagnostic().WithLocation(12, 16);
             await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
         [Theory]
-        [MemberData(nameof(GetTestExpressions), "")]
+        [MemberData(nameof(GetTestExpressions), "", "")]
         [MemberData(nameof(ValidTestExpressions))]
-        public async Task TestValidExpressionAsync(string expression, int column)
+        public async Task TestValidExpressionAsync(string expression, string fixedExpression, int column)
         {
             var testCode = $@"
 class Foo
@@ -149,8 +180,8 @@ public void Baz()
         }
 
         [Theory]
-        [MemberData(nameof(GetTestExpressions), "\r\n")]
-        public async Task TestInvalidExpressionAsync(string expression, int column)
+        [MemberData(nameof(GetTestExpressions), "\r\n", "\r\n            ")]
+        public async Task TestInvalidExpressionAsync(string expression, string fixedExpression, int column)
         {
             var testCode = $@"
 class Foo
@@ -164,11 +195,27 @@ public void Baz()
         {expression};
     }}
 
+    public long this[int a, int s] => a + s;
+}}";
+            var fixedCode = $@"
+class Foo
+{{
+    public void Bar(int i, int z)
+    {{
+    }}
+
+    public void Baz()
+    {{
+        {fixedExpression};
+    }}
+
     public long this[int a, int s] => a + s;
 }}";
 
             DiagnosticResult expected = this.CSharpDiagnostic().WithLocation(10, column);
             await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
         [Fact]
@@ -228,15 +275,39 @@ public MyAttribute(int a, int b)
       2)]
 class Foo
 {
+}";
+            var fixedCode = @"
+[System.AttributeUsage(System.AttributeTargets.Class)]
+public class MyAttribute : System.Attribute
+{
+    public MyAttribute(int a, int b)
+    {
+    }
+}
+
+[MyAttribute(
+    1,
+      2)]
+class Foo
+{
 }";
 
             DiagnosticResult expected = this.CSharpDiagnostic().WithLocation(10, 14);
             await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
+        /// <inheritdoc/>
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {
             yield return new SA1116SplitParametersMustStartOnLineAfterDeclaration();
         }
+
+        /// <inheritdoc/>
+        protected override CodeFixProvider GetCSharpCodeFixProvider()
+        {
+            return new SA1116CodeFixProvider();
+        }
     }
 }

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/ReadabilityResources.resx

@@ -282,6 +282,9 @@
   <data name="SA1115Title" xml:space="preserve">
     <value>Parameter must follow comma</value>
   </data>
+  <data name="SA1116CodeFix" xml:space="preserve">
+    <value>Move first argument to next line</value>
+  </data>
   <data name="SA1116Description" xml:space="preserve">
     <value>The parameters to a C# method or indexer call or declaration span across multiple lines, but the first parameter does not start on the line after the opening bracket.</value>
   </data>

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/SA1116CodeFixProvider.cs

@@ -0,0 +1,86 @@
+namespace StyleCop.Analyzers.ReadabilityRules
+{
+    using System.Collections.Immutable;
+    using System.Composition;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Helpers;
+    using Microsoft.CodeAnalysis;
+    using Microsoft.CodeAnalysis.CodeActions;
+    using Microsoft.CodeAnalysis.CodeFixes;
+    using Microsoft.CodeAnalysis.CSharp;
+    using Microsoft.CodeAnalysis.Text;
+
+    /// <summary>
+    /// Implements a code fix for <see cref="SA1116SplitParametersMustStartOnLineAfterDeclaration"/>.
+    /// </summary>
+    /// <remarks>
+    /// <para>To fix a violation of this rule, ensure that the first parameter starts on the line after the opening
+    /// bracket, or place all parameters on the same line if the parameters are not too long.</para>
+    /// </remarks>
+    [ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(SA1116CodeFixProvider))]
+    [Shared]
+    public class SA1116CodeFixProvider : CodeFixProvider
+    {
+        /// <inheritdoc/>
+        public override ImmutableArray<string> FixableDiagnosticIds { get; } =
+            ImmutableArray.Create(SA1116SplitParametersMustStartOnLineAfterDeclaration.DiagnosticId);
+
+        /// <inheritdoc/>
+        public override FixAllProvider GetFixAllProvider()
+        {
+            return CustomFixAllProviders.BatchFixer;
+        }
+
+        /// <inheritdoc/>
+        public override Task RegisterCodeFixesAsync(CodeFixContext context)
+        {
+            foreach (var diagnostic in context.Diagnostics)
+            {
+                if (!diagnostic.Id.Equals(SA1116SplitParametersMustStartOnLineAfterDeclaration.DiagnosticId))
+                {
+                    continue;
+                }
+
+                context.RegisterCodeFix(
+                    CodeAction.Create(
+                        ReadabilityResources.SA1116CodeFix,
+                        cancellationToken => GetTransformedDocumentAsync(context.Document, diagnostic, cancellationToken),
+                        equivalenceKey: nameof(SA1116CodeFixProvider)),
+                    diagnostic);
+            }
+
+            return SpecializedTasks.CompletedTask;
+        }
+
+        private static async Task<Document> GetTransformedDocumentAsync(Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
+        {
+            SyntaxNode root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+            SyntaxToken originalToken = root.FindToken(diagnostic.Location.SourceSpan.Start);
+
+            SyntaxTree tree = root.SyntaxTree;
+            SourceText sourceText = await tree.GetTextAsync(cancellationToken).ConfigureAwait(false);
+            TextLine sourceLine = sourceText.Lines.GetLineFromPosition(originalToken.SpanStart);
+
+            string lineText = sourceText.ToString(sourceLine.Span);
+            int indentLength;
+            for (indentLength = 0; indentLength < lineText.Length; indentLength++)
+            {
+                if (!char.IsWhiteSpace(lineText[indentLength]))
+                {
+                    break;
+                }
+            }
+
+            IndentationOptions indentationOptions = IndentationOptions.FromDocument(document);
+            SyntaxTriviaList newTrivia =
+                SyntaxFactory.TriviaList(
+                    SyntaxFactory.CarriageReturnLineFeed,
+                    SyntaxFactory.Whitespace(lineText.Substring(0, indentLength) + IndentationHelper.GenerateIndentationString(indentationOptions, 1)));
+
+            SyntaxToken updatedToken = originalToken.WithLeadingTrivia(originalToken.LeadingTrivia.AddRange(newTrivia));
+            SyntaxNode updatedRoot = root.ReplaceToken(originalToken, updatedToken);
+            return document.WithSyntaxRoot(updatedRoot);
+        }
+    }
+}

StyleCop.Analyzers/StyleCop.Analyzers/StyleCop.Analyzers.csproj

@@ -297,6 +297,7 @@
     <Compile Include="ReadabilityRules\SA1113CommaMustBeOnSameLineAsPreviousParameter.cs" />
     <Compile Include="ReadabilityRules\SA1114ParameterListMustFollowDeclaration.cs" />
     <Compile Include="ReadabilityRules\SA1115ParameterMustFollowComma.cs" />
+    <Compile Include="ReadabilityRules\SA1116CodeFixProvider.cs" />
     <Compile Include="ReadabilityRules\SA1116SplitParametersMustStartOnLineAfterDeclaration.cs" />
     <Compile Include="ReadabilityRules\SA1117ParametersMustBeOnSameLineOrSeparateLines.cs" />
     <Compile Include="ReadabilityRules\SA1118ParameterMustNotSpanMultipleLines.cs" />