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Preserve attribute inheritance behavior in the MA0179 code fix #1457

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Merged
meziantou merged 1 commit into from
Sep 11, 2026
Merged

Preserve attribute inheritance behavior in the MA0179 code fix #1457

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18 changes: 18 additions & 0 deletions docs/Rules/MA0179.md
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Original file line number Diff line number Diff line change
Expand Up @@ -45,3 +45,21 @@ if (attr != null)
_ = attr.Message;
}
````

## Attribute inheritance on properties and events

The instance methods `MemberInfo.GetCustomAttributes(bool)` and `MemberInfo.GetCustomAttributes(Type, bool)` ignore the `inherit` parameter for properties and events, whereas `Attribute.IsDefined(MemberInfo, Type, bool)` also searches the overridden properties and events when `inherit` is `true`. To keep the same behavior, the code fix uses the instance method `MemberInfo.IsDefined(Type, bool)` when the member can be a property or an event and `inherit` is not `false`:

````csharp
using System;
using System.Reflection;

void Sample(MemberInfo member)
{
// non-compliant
_ = member.GetCustomAttributes(typeof(ObsoleteAttribute), inherit: true).Length > 0;

// compliant (fixed code)
_ = member.IsDefined(typeof(ObsoleteAttribute), inherit: true);
}
````
45 changes: 38 additions & 7 deletions src/Meziantou.Analyzer.CodeFixers/Rules/UseAttributeIsDefinedFixer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -271,7 +271,7 @@ private static SyntaxNode CreateAttributeIsDefinedInvocation(SyntaxGenerator gen
arguments.Add(typeSyntax);

// Find inherit argument
SyntaxNode? inheritSyntax = null;
IArgumentOperation? inheritArgument = null;
foreach (var arg in invocation.Arguments)
{
// Skip instance argument for extension methods
Expand All @@ -284,19 +284,30 @@ private static SyntaxNode CreateAttributeIsDefinedInvocation(SyntaxGenerator gen

if (arg.Parameter?.Type.SpecialType == SpecialType.System_Boolean && arg.Parameter.Name == "inherit")
{
inheritSyntax = arg.Syntax;
inheritArgument = arg;
break;
}
}

if (inheritSyntax is not null)
SyntaxNode isDefinedInvocation;
if (instanceSyntax is not null && inheritArgument is not null && MustUseInstanceIsDefined(semanticModel.Compilation, invocation, inheritArgument))
{
arguments.Add(inheritSyntax);
isDefinedInvocation = generator.InvocationExpression(
generator.MemberAccessExpression(instanceSyntax, "IsDefined"),
typeSyntax,
inheritArgument.Syntax);
}
else
{
if (inheritArgument is not null)
{
arguments.Add(inheritArgument.Syntax);
}

var isDefinedInvocation = generator.InvocationExpression(
generator.MemberAccessExpression(attributeTypeSyntax, "IsDefined"),
arguments);
isDefinedInvocation = generator.InvocationExpression(
generator.MemberAccessExpression(attributeTypeSyntax, "IsDefined"),
arguments);
}

if (negate)
{
Expand All @@ -305,4 +316,24 @@ private static SyntaxNode CreateAttributeIsDefinedInvocation(SyntaxGenerator gen

return isDefinedInvocation;
}

// The instance methods, such as MemberInfo.GetCustomAttributes(Type, bool), ignore 'inherit' for properties and events,
// while Attribute.IsDefined(MemberInfo, Type, bool) walks the chain of the overridden properties and events.
// MemberInfo.IsDefined(Type, bool) behaves like the instance methods, so it is used when the results could differ.
private static bool MustUseInstanceIsDefined(Compilation compilation, IInvocationOperation invocation, IArgumentOperation inheritArgument)
{
if (invocation.Instance?.Type is not { } instanceType)
return false;

if (inheritArgument.Value.ConstantValue is { HasValue: true, Value: false })
return false;

return CanBeInstanceOf(instanceType, compilation.GetBestTypeByMetadataName("System.Reflection.PropertyInfo")) ||
CanBeInstanceOf(instanceType, compilation.GetBestTypeByMetadataName("System.Reflection.EventInfo"));

static bool CanBeInstanceOf(ITypeSymbol type, INamedTypeSymbol? expectedType)
{
return expectedType is not null && (type.IsOrInheritsFrom(expectedType) || expectedType.IsOrInheritsFrom(type));
}
}
}
173 changes: 170 additions & 3 deletions tests/Meziantou.Analyzer.Test/Rules/UseAttributeIsDefinedAnalyzerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -853,7 +853,7 @@ class TestClass
{
void Test(MemberInfo member)
{
_ = Attribute.IsDefined(member, typeof(ObsoleteAttribute), inherit: true);
_ = member.IsDefined(typeof(ObsoleteAttribute), inherit: true);
}
}
""";
Expand Down Expand Up @@ -885,7 +885,7 @@ class TestClass
{
void Test(MemberInfo member)
{
_ = Attribute.IsDefined(member, typeof(Attribute), inherit: true);
_ = member.IsDefined(typeof(Attribute), inherit: true);
}
}
""";
Expand Down Expand Up @@ -987,7 +987,174 @@ class TestClass
{
void Test(MemberInfo member)
{
_ = Attribute.IsDefined(member, typeof(ObsoleteAttribute), inherit: true);
_ = member.IsDefined(typeof(ObsoleteAttribute), inherit: true);
}
}
""";

return test.RunAsync();
}

[Theory]
[InlineData("PropertyInfo")]
[InlineData("EventInfo")]
public Task InstanceGetCustomAttributes_WithInherit_PropertyOrEvent_UsesInstanceIsDefined(string memberType)
{
var test = CreateTest();
test.TestCode = $$"""
using System;
using System.Reflection;

class TestClass
{
void Test({{memberType}} member)
{
_ = {|MA0179:member.GetCustomAttributes(typeof(ObsoleteAttribute), true).Length > 0|};
}
}
""";
test.FixedCode = $$"""
using System;
using System.Reflection;

class TestClass
{
void Test({{memberType}} member)
{
_ = member.IsDefined(typeof(ObsoleteAttribute), true);
}
}
""";

return test.RunAsync();
}

[Fact]
public Task InstanceGetCustomAttributes_WithNonConstantInherit_UsesInstanceIsDefined()
{
var test = CreateTest();
test.TestCode = """
using System;
using System.Reflection;

class TestClass
{
void Test(MemberInfo member, bool inherit)
{
_ = {|MA0179:member.GetCustomAttributes(typeof(ObsoleteAttribute), inherit).Length == 0|};
}
}
""";
test.FixedCode = """
using System;
using System.Reflection;

class TestClass
{
void Test(MemberInfo member, bool inherit)
{
_ = !member.IsDefined(typeof(ObsoleteAttribute), inherit);
}
}
""";

return test.RunAsync();
}

[Fact]
public Task InstanceGetCustomAttributes_WithoutInherit_Property_UsesAttributeIsDefined()
{
var test = CreateTest();
test.TestCode = """
using System;
using System.Reflection;

class TestClass
{
void Test(PropertyInfo member)
{
_ = {|MA0179:member.GetCustomAttributes(typeof(ObsoleteAttribute), inherit: false).Length > 0|};
}
}
""";
test.FixedCode = """
using System;
using System.Reflection;

class TestClass
{
void Test(PropertyInfo member)
{
_ = Attribute.IsDefined(member, typeof(ObsoleteAttribute), inherit: false);
}
}
""";

return test.RunAsync();
}

[Theory]
[InlineData("Type")]
[InlineData("MethodInfo")]
[InlineData("FieldInfo")]
public Task InstanceGetCustomAttributes_WithInherit_NotPropertyOrEvent_UsesAttributeIsDefined(string memberType)
{
var test = CreateTest();
test.TestCode = $$"""
using System;
using System.Reflection;

class TestClass
{
void Test({{memberType}} member)
{
_ = {|MA0179:member.GetCustomAttributes(typeof(ObsoleteAttribute), true).Length > 0|};
}
}
""";
test.FixedCode = $$"""
using System;
using System.Reflection;

class TestClass
{
void Test({{memberType}} member)
{
_ = Attribute.IsDefined(member, typeof(ObsoleteAttribute), true);
}
}
""";

return test.RunAsync();
}

[Fact]
public Task ExtensionGetCustomAttributes_Property_UsesAttributeIsDefined()
{
var test = CreateTest();
test.TestCode = """
using System;
using System.Linq;
using System.Reflection;

class TestClass
{
void Test(PropertyInfo member)
{
_ = {|MA0179:member.GetCustomAttributes(typeof(ObsoleteAttribute)).Any()|};
}
}
""";
test.FixedCode = """
using System;
using System.Linq;
using System.Reflection;

class TestClass
{
void Test(PropertyInfo member)
{
_ = Attribute.IsDefined(member, typeof(ObsoleteAttribute));
}
}
""";
Expand Down