Interface Qualifier

interpreter/attributes.go:67–86

Qualifier marker interface for designating different qualifier values and where they appear within field selections and index call expressions (`_[_]`).

// Qualifier marker interface for designating different qualifier values and where they appear
// within field selections and index call expressions (`_[_]`).
type Qualifier interface {
	// ID where the qualifier appears within an expression.
	ID() int64

	// IsOptional specifies whether the qualifier is optional.
	// Instead of a direct qualification, an optional qualifier will be resolved via QualifyIfPresent
	// rather than Qualify. A non-optional qualifier may also be resolved through QualifyIfPresent if
	// the object to qualify is itself optional.
	IsOptional() bool

	// Qualify performs a qualification, e.g. field selection, on the input object and returns
	// the value of the access and whether the value was set. A non-nil value with a false presence
	// test result indicates that the value being returned is the default value.
	Qualify(vars Activation, obj any) (any, error)

	// QualifyIfPresent qualifies the object if the qualifier is declared or defined on the object.
	// The 'presenceOnly' flag indicates that the value is not necessary, just a boolean status as
	// to whether the qualifier is present.
	QualifyIfPresent(vars Activation, obj any, presenceOnly bool) (any, bool, error)
}

// ConstantQualifier interface embeds the Qualifier interface and provides an option to inspect the
// qualifier's constant value.