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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Collections.Immutable;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.CSharp.SimplifyPropertyPattern;
using static SyntaxFactory;
[ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.SimplifyPropertyPattern), Shared]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed class CSharpSimplifyPropertyPatternCodeFixProvider() : SyntaxEditorBasedCodeFixProvider
{
public override ImmutableArray<string> FixableDiagnosticIds { get; } =
[IDEDiagnosticIds.SimplifyPropertyPatternDiagnosticId];
public override Task RegisterCodeFixesAsync(CodeFixContext context)
{
RegisterCodeFix(context, CSharpAnalyzersResources.Simplify_property_pattern, nameof(CSharpAnalyzersResources.Simplify_property_pattern));
return Task.CompletedTask;
}
protected override Task FixAllAsync(
Document document, ImmutableArray<Diagnostic> diagnostics,
SyntaxEditor editor, CancellationToken cancellationToken)
{
// Process subpatterns in reverse order so we rewrite from inside-to-outside with nested
// patterns.
var subpatterns = diagnostics.Select(d => (SubpatternSyntax)d.AdditionalLocations[0].FindNode(cancellationToken))
.OrderByDescending(s => s.SpanStart)
.ToImmutableArray();
foreach (var subpattern in subpatterns)
{
editor.ReplaceNode(
subpattern,
(current, _) =>
{
var currentSubpattern = (SubpatternSyntax)current;
var simplified = TrySimplify(currentSubpattern);
return simplified ?? currentSubpattern;
});
}
return Task.CompletedTask;
}
private static SubpatternSyntax? TrySimplify(SubpatternSyntax currentSubpattern)
{
if (!SimplifyPropertyPatternHelpers.IsSimplifiable(currentSubpattern, out var innerSubpattern, out var outerExpressionColon))
return null;
// attempt to simplify the inner pattern we're pointing at as well (that way if the user
// invokes the fix on a top level property, we collapse as far inwards as possible).
innerSubpattern = TrySimplify(innerSubpattern) ?? innerSubpattern;
var innerExpressionColon = innerSubpattern.ExpressionColon;
if (!SimplifyPropertyPatternHelpers.IsMergable(outerExpressionColon.Expression) ||
!SimplifyPropertyPatternHelpers.IsMergable(innerExpressionColon?.Expression))
{
return null;
}
var merged = Merge(outerExpressionColon, innerExpressionColon);
if (merged == null)
return null;
return currentSubpattern.WithExpressionColon(merged)
.WithPattern(innerSubpattern.Pattern)
.WithAdditionalAnnotations(Formatter.Annotation);
}
private static BaseExpressionColonSyntax? Merge(BaseExpressionColonSyntax outerExpressionColon, BaseExpressionColonSyntax innerExpressionColon)
{
var merged = Merge(outerExpressionColon.Expression, innerExpressionColon.Expression);
if (merged == null)
return null;
return outerExpressionColon.WithExpression(merged);
}
private static MemberAccessExpressionSyntax? Merge(ExpressionSyntax? outerExpression, ExpressionSyntax? innerExpression)
{
if (outerExpression == null || innerExpression == null)
return null;
// if the inner name is simple (i.e. just 'X') we can trivially form the final member
// access by joining the two names together.
if (innerExpression is SimpleNameSyntax innerName)
return MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, outerExpression, innerName);
if (innerExpression is not MemberAccessExpressionSyntax innerMemberAccess)
return null;
// otherwise, attempt to decompose the inner expression, joining that with the outer until we get
// the result.
return Merge(Merge(outerExpression, innerMemberAccess.Expression), innerMemberAccess.Name);
}
}
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