File: src\Analyzers\CSharp\Tests\MakeStructFieldsWritable\MakeStructFieldsWritableTests.cs
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Project: src\src\CodeStyle\CSharp\Tests\Microsoft.CodeAnalysis.CSharp.CodeStyle.UnitTests.csproj (Microsoft.CodeAnalysis.CSharp.CodeStyle.UnitTests)
// 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.Threading.Tasks;
using Microsoft.CodeAnalysis.CSharp.MakeStructFieldsWritable;
using Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions;
using Microsoft.CodeAnalysis.Test.Utilities;
using Roslyn.Test.Utilities;
using Xunit;
 
namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.MakeStructFieldsWritable;
 
using VerifyCS = CSharpCodeFixVerifier<CSharpMakeStructFieldsWritableDiagnosticAnalyzer, CSharpMakeStructFieldsWritableCodeFixProvider>;
 
[Trait(Traits.Feature, Traits.Features.CodeActionsMakeStructFieldsWritable)]
public class MakeStructFieldsWritable
{
    [Theory, CombinatorialData]
    public void TestStandardProperty(AnalyzerProperty property)
        => VerifyCS.VerifyStandardProperty(property);
 
    [Fact]
    public async Task SingleReadonlyField_ThisAssignmentInMethod()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """);
    }
 
    [Fact]
    public async Task SingleReadonlyField_ThisAssignmentInMultipleMethods()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                public void Test2()
                {
                    this = new MyStruct(10);
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                public void Test2()
                {
                    this = new MyStruct(10);
                }
            }
            """);
    }
 
    [Fact]
    public async Task SingleNonReadonlyField_ThisAssignmentInMethod()
    {
        var code = """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task MultipleMixedFields_ThisAssignmentInMethod()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int First;
                public readonly int Second;
                public int Third;
 
                public MyStruct(int first, int second, int third)
                {
                    First = first;
                    Second = second;
                    Third = third;
                }
 
                public void Test()
                {
                    this = new MyStruct(5, 3, 1);
                }
            }
            """,
            """
            struct MyStruct
            {
                public int First;
                public int Second;
                public int Third;
 
                public MyStruct(int first, int second, int third)
                {
                    First = first;
                    Second = second;
                    Third = third;
                }
 
                public void Test()
                {
                    this = new MyStruct(5, 3, 1);
                }
            }
            """);
    }
 
    [Fact]
    public async Task SingleReadonlyField_ThisAssignmentInCtor()
    {
        var code = """
            struct MyStruct
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    this = new MyStruct(value, 0);
                }
 
                public MyStruct(int first, int second)
                {
                    Value = first;
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task SingleReadonlyField_NoThisAssignment()
    {
        var code = """
            struct MyStruct
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task SingleReadonlyField_ThisAssignmentInMethod_ReportDiagnostic()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """);
    }
 
    [Fact]
    public async Task SingleReadonlyField_InClass()
    {
        var code = """
            class MyClass
            {
                public readonly int Value;
 
                public MyClass(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    // error CS1604: Cannot assign to 'this' because it is read-only
                    {|CS1604:this|} = new MyClass(5);
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task StructWithoutField()
    {
        var code = """
            struct MyStruct
            {
                public void Test()
                {
                    this = new MyStruct();
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task SingleProperty_ThisAssignmentInMethod()
    {
        var code = """
            struct MyStruct
            {
                public int Value { get; set; }
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task SingleGetterProperty_ThisAssignmentInMethod()
    {
        var code = """
            struct MyStruct
            {
                public int Value { get; }
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
            """;
 
        await VerifyCS.VerifyCodeFixAsync(code, code);
    }
 
    [Fact]
    public async Task MultipleStructDeclaration_SingleReadonlyField_ThisAssignmentInMethod()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
 
            struct [|MyStruct2|]
            {
                public readonly int Value;
 
                public MyStruct2(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct2(5);
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
 
            struct MyStruct2
            {
                public int Value;
 
                public MyStruct2(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct2(5);
                }
            }
            """);
    }
 
    [Fact]
    public async Task MultipleStructDeclaration_SingleReadonlyField_ThisAssignmentInMethod_ShouldNotReportDiagnostic()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
 
            struct [|MyStruct2|]
            {
                public readonly int Value;
 
                public MyStruct2(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct2(5);
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
            }
 
            struct MyStruct2
            {
                public int Value;
 
                public MyStruct2(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct2(5);
                }
            }
            """);
    }
 
    [Fact]
    public async Task NestedStructDeclaration_SingleNestedReadonlyField_ThisAssignmentInMethod()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                struct [|NestedStruct|]
                {
                    public readonly int NestedValue;
 
                    public NestedStruct(int nestedValue)
                    {
                        NestedValue = nestedValue;
                    }
 
                    public void Test()
                    {
                        this = new NestedStruct(5);
                    }
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                struct NestedStruct
                {
                    public int NestedValue;
 
                    public NestedStruct(int nestedValue)
                    {
                        NestedValue = nestedValue;
                    }
 
                    public void Test()
                    {
                        this = new NestedStruct(5);
                    }
                }
            }
            """);
    }
 
    [Fact]
    public async Task NestedStructDeclaration_SingleReadonlyField_ThisAssignmentInMethod()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                struct [|NestedStruct|]
                {
                    public readonly int NestedValue;
 
                    public NestedStruct(int nestedValue)
                    {
                        NestedValue = nestedValue;
                    }
 
                    public void Test()
                    {
                        this = new NestedStruct(5);
                    }
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public MyStruct(int value)
                {
                    Value = value;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                struct NestedStruct
                {
                    public int NestedValue;
 
                    public NestedStruct(int nestedValue)
                    {
                        NestedValue = nestedValue;
                    }
 
                    public void Test()
                    {
                        this = new NestedStruct(5);
                    }
                }
            }
            """);
    }
 
    [Fact]
    public async Task StructDeclaration_MixedFields_MixedAssignmentsInMethods()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
                public int TestValue;
 
                public MyStruct(int value)
                {
                    Value = value;
                    TestValue = 100;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                public void Test2()
                {
                    TestValue = 0;
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
                public int TestValue;
 
                public MyStruct(int value)
                {
                    Value = value;
                    TestValue = 100;
                }
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                public void Test2()
                {
                    TestValue = 0;
                }
            }
            """);
    }
 
    [Fact]
    public async Task StructDeclaration_ChangedOrderOfConstructorDeclaration()
    {
        await VerifyCS.VerifyCodeFixAsync(
            """
            struct [|MyStruct|]
            {
                public readonly int Value;
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                public MyStruct(int value)
                {
                    Value = value;
                }
            }
            """,
            """
            struct MyStruct
            {
                public int Value;
 
                public void Test()
                {
                    this = new MyStruct(5);
                }
 
                public MyStruct(int value)
                {
                    Value = value;
                }
            }
            """);
    }
 
    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/57920")]
    public async Task ReadonlyStaticField()
    {
        var test = """
            struct Repro
            {
                public static readonly Repro DefaultValue = new Repro();
 
                public int IrrelevantValue;
 
                public void Overwrite(Repro other) => this = other;
            }
            """;
        await VerifyCS.VerifyCodeFixAsync(test, test);
    }
 
    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/57920")]
    public async Task ConstField()
    {
        var test = """
            struct Repro
            {
                public const int X = 0;
 
                public int IrrelevantValue;
 
                public void Overwrite(Repro other) => this = other;
            }
            """;
        await VerifyCS.VerifyCodeFixAsync(test, test);
    }
}