Add IndentationCodeFixProvider

Currently this code fix only corrects SA1137, but the implementation is
general enough to support other types of indentation corrections in the
future.

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/ReadabilityRules/IndentationCodeFixProvider.cs

@@ -0,0 +1,119 @@
+// Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
+// Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+namespace StyleCop.Analyzers.ReadabilityRules
+{
+    using System.Collections.Generic;
+    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.Text;
+
+    [ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(IndentationCodeFixProvider))]
+    [Shared]
+    internal class IndentationCodeFixProvider : CodeFixProvider
+    {
+        /// <inheritdoc/>
+        public override ImmutableArray<string> FixableDiagnosticIds { get; } =
+            ImmutableArray.Create(SA1137ElementsShouldHaveTheSameIndentation.DiagnosticId);
+
+        /// <inheritdoc/>
+        public sealed override FixAllProvider GetFixAllProvider() =>
+            FixAll.Instance;
+
+        /// <inheritdoc/>
+        public override Task RegisterCodeFixesAsync(CodeFixContext context)
+        {
+            foreach (var diagnostic in context.Diagnostics)
+            {
+                context.RegisterCodeFix(
+                    CodeAction.Create(
+                        ReadabilityResources.IndentationCodeFix,
+                        cancellationToken => GetTransformedDocumentAsync(context.Document, diagnostic, cancellationToken),
+                        nameof(IndentationCodeFixProvider)),
+                    diagnostic);
+            }
+
+            return SpecializedTasks.CompletedTask;
+        }
+
+        private static async Task<Document> GetTransformedDocumentAsync(Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
+        {
+            var syntaxRoot = await document.GetSyntaxRootAsync().ConfigureAwait(false);
+
+            TextChange textChange;
+            if (!TryGetTextChange(diagnostic, syntaxRoot, out textChange))
+            {
+                return document;
+            }
+
+            var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+            return document.WithText(text.WithChanges(textChange));
+        }
+
+        private static bool TryGetTextChange(Diagnostic diagnostic, SyntaxNode syntaxRoot, out TextChange textChange)
+        {
+            string replacement;
+            if (!diagnostic.Properties.TryGetValue(SA1137ElementsShouldHaveTheSameIndentation.ExpectedIndentationKey, out replacement))
+            {
+                textChange = default(TextChange);
+                return false;
+            }
+
+            var trivia = syntaxRoot.FindTrivia(diagnostic.Location.SourceSpan.Start);
+
+            TextSpan originalSpan;
+            if (trivia == default(SyntaxTrivia))
+            {
+                originalSpan = trivia.Span;
+            }
+            else
+            {
+                originalSpan = new TextSpan(diagnostic.Location.SourceSpan.Start, 0);
+            }
+
+            textChange = new TextChange(originalSpan, replacement);
+            return true;
+        }
+
+        private class FixAll : DocumentBasedFixAllProvider
+        {
+            public static FixAllProvider Instance { get; } =
+                new FixAll();
+
+            protected override string CodeActionTitle =>
+                ReadabilityResources.IndentationCodeFix;
+
+            protected override async Task<SyntaxNode> FixAllInDocumentAsync(FixAllContext fixAllContext, Document document, ImmutableArray<Diagnostic> diagnostics)
+            {
+                if (diagnostics.IsEmpty)
+                {
+                    return null;
+                }
+
+                var syntaxRoot = await document.GetSyntaxRootAsync().ConfigureAwait(false);
+
+                List<TextChange> changes = new List<TextChange>();
+
+                foreach (var diagnostic in diagnostics)
+                {
+                    TextChange textChange;
+                    if (TryGetTextChange(diagnostic, syntaxRoot, out textChange))
+                    {
+                        changes.Add(textChange);
+                    }
+                }
+
+                changes.Sort((left, right) => left.Span.Start.CompareTo(right.Span.Start));
+
+                var text = await document.GetTextAsync().ConfigureAwait(false);
+                return await document.WithText(text.WithChanges(changes)).GetSyntaxRootAsync(fixAllContext.CancellationToken).ConfigureAwait(false);
+            }
+        }
+    }
+}

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

@@ -108,6 +108,7 @@
     <Compile Include="OrderingRules\SA1212SA1213CodeFixProvider.cs" />
     <Compile Include="OrderingRules\UsingCodeFixProvider.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="ReadabilityRules\IndentationCodeFixProvider.cs" />
     <Compile Include="ReadabilityRules\RemoveRegionCodeFixProvider.cs" />
     <Compile Include="ReadabilityRules\RemoveRegionFixAllProvider.cs" />
     <Compile Include="ReadabilityRules\SA1100CodeFixProvider.cs" />

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/ReadabilityResources.Designer.cs

@@ -117,6 +117,9 @@
   <resheader name="writer">
     <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
+  <data name="IndentationCodeFix" xml:space="preserve">
+    <value>Fix indentation</value>
+  </data>
   <data name="RemoveRegionCodeFix" xml:space="preserve">
     <value>Remove region</value>
   </data>