Custom Attributes

Extension scripts usually rely on custom attributes to control their behaviour. A script can define any amount of attributes.

Defining custom attributes

In order to support custom attributes, extension script should provide an attribute descriptor.

Here is the attribute descriptor definition example:

namespace Igor.TypeScript
{
    [CustomAttributes]
    public class MyCustomAttributes
    {
        public static readonly BoolAttributeDescriptor MyAttribute =
            new BoolAttributeDescriptor("my_attribute", IgorAttributeTargets.Any, AttributeInheritance.Scope);
    }
}

Attribute descriptors should be defined as public static readonly fields. The class containing them should be marked with [CustomAttributes] attribute. It can be the same class that implements generator extension interface or a different one.

To define a custom attribute descriptor, you need to know the type, the name, the usage target and the inheritance type.

The following attribute types are supported:

Attribute type	AttributeDescriptor type
bool	BoolAttributeDescriptor
int	IntAttributeDescriptor
double	FloatAttributeDescriptor
string	StringAttributeDescriptor
enum	EnumAttributeDescriptor<EnumType>

See Attribute Inheritance for inheritance types.

Accessing attribute value

Use Attribute function on an AST type to access attribute value:

// Provide the default value
bool myValue = ast.Attribute(MyCustomAttributes.MyAttribute, false);

// No default value, returns nullable
bool? myValue = ast.Attribute(MyCustomAttributes.MyAttribute);

Enum attributes

To support custom enum attributes, extension script should declare enum type first and then provide an instance of EnumAttributeDescriptor:

enum MyAttributeValue
{
    // by default, Igor attribute value is lowercased: none
    None,

    // provide explicit Igor attribute value
    [IgorEnumValue("my_value")]
    MyValue,
}

[CustomAttributes]
public class MyCustomAttributes
{
    public static readonly EnumAttributeDescriptor<MyAttributeValue> MyAttribute =
        new EnumAttributeDescriptor<MyAttributeValue>("my_attribute", IgorAttributeTargets.Any);
}

Usage example:

[* my_attribute=my_value]
module ScriptSample
{
}