Roslyn: is ISymbol.GetAttributes returns inherited attributes

Question

Roslyn has ISymbol interface with various useful methods. I'm trying to get all class attributes via ISymbol.GetAttributes. This is a documentation link:

https://learn.microsoft.com/de-de/dotnet/api/microsoft.codeanalysis.isymbol.getattributes?view=roslyn-dotnet

As we can see there is no indication if this method returns inherited attributes (attributes from base classes) or not. So this is the first questions. The second question - why there is no mentions about that in documentation?

Answer 1

I don't know why there's no mention of it in the documentation, and think it should be mentioned there.

Since I was facing the same issue, I tested it, and it will not return inherited attributes. You can use these extension methods to get all attributes including the inherited ones:

public static IEnumerable<AttributeData> GetAttributesWithInherited(this INamedTypeSymbol typeSymbol) {
    foreach (var attribute in typeSymbol.GetAttributes()) {
        yield return attribute;
    }

    var baseType = typeSymbol.BaseType;
    while (baseType != null) {
        foreach (var attribute in baseType.GetAttributes()) {
            if (IsInherited(attribute)) {
                yield return attribute;
            }
        }

        baseType = baseType.BaseType;
    }
}

private static bool IsInherited(this AttributeData attribute) {
    if (attribute.AttributeClass == null) {
        return false;
    }

    foreach (var attributeAttribute in attribute.AttributeClass.GetAttributes()) {
        var @class = attributeAttribute.AttributeClass;
        if (@class != null && @class.Name == nameof(AttributeUsageAttribute) &&
            @class.ContainingNamespace?.Name == "System") {
            foreach (var kvp in attributeAttribute.NamedArguments) {
                if (kvp.Key == nameof(AttributeUsageAttribute.Inherited)) {
                    return (bool) kvp.Value.Value!;
                }
            }

            // Default value of Inherited is true
            return true;
        }
    }

    // An attribute without an `AttributeUsage` attribute will also default to being inherited.
    return true;
}