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Add test for implicit params array in AppendLine with AppendFormat #1021

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Merged
meziantou merged 1 commit into from
Feb 20, 2026
Merged

Add test for implicit params array in AppendLine with AppendFormat #1021

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8 changes: 7 additions & 1 deletion src/Meziantou.Analyzer.CodeFixers/Rules/OptimizeStringBuilderUsageFixer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Operations;
using Microsoft.CodeAnalysis.Simplification;

namespace Meziantou.Analyzer.Rules;

Expand Down Expand Up @@ -253,8 +254,13 @@ private static async Task<Document> ReplaceStringFormatWithAppendFormat(Document

var stringFormatOperation = (IInvocationOperation)operation.Arguments[0].Value;

var stringFormatSyntax = (InvocationExpressionSyntax)stringFormatOperation.Syntax;
var arguments = stringFormatSyntax.ArgumentList.Arguments
.Select(static argument => (SyntaxNode)argument.WithAdditionalAnnotations(Simplifier.Annotation))
.ToArray();

var newExpression = generator.InvocationExpression(generator.MemberAccessExpression(operation.GetChildOperations().First().Syntax, "AppendFormat"),
[.. stringFormatOperation.Arguments.Select(a => a.Syntax)]);
[.. arguments]);

if (isAppendLine)
{
Expand Down
33 changes: 33 additions & 0 deletions tests/Meziantou.Analyzer.Test/Rules/OptimizeStringBuilderUsageAnalyzerTests.cs
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Expand Up @@ -575,6 +575,39 @@ void A()
.ValidateAsync();
}

[Fact]
public async Task AppendLine_AppendFormat_ImplicitParamsArray()
{
await CreateProjectBuilder()
.WithSourceCode(
"""
using System.Globalization;
using System.Text;

class Test
{
void A()
{
[||]new StringBuilder().AppendLine(string.Format(CultureInfo.InvariantCulture, "{0} {1} {2} {3}", string.Empty, "MilliSec", "%", "Comment"));
}
}
""")
.ShouldFixCodeWith(
"""
using System.Globalization;
using System.Text;

class Test
{
void A()
{
new StringBuilder().AppendFormat(CultureInfo.InvariantCulture, "{0} {1} {2} {3}", string.Empty, "MilliSec", "%", "Comment").AppendLine();
}
}
""")
.ValidateAsync();
}

[Fact]
public async Task Append_StringJoin_AppendJoin_OldTargetFramework()
{
Expand Down