[github/fretlink/terraform-provider-statuscake.git] / vendor / github.com / zclconf / go-cty / cty / function / unpredictable.go

package function

import (
	"github.com/zclconf/go-cty/cty"
)

// Unpredictable wraps a given function such that it retains the same arguments
// and type checking behavior but will return an unknown value when called.
//
// It is recommended that most functions be "pure", which is to say that they
// will always produce the same value given particular input. However,
// sometimes it is necessary to offer functions whose behavior depends on
// some external state, such as reading a file or determining the current time.
// In such cases, an unpredictable wrapper might be used to stand in for
// the function during some sort of prior "checking" phase in order to delay
// the actual effect until later.
//
// While Unpredictable can support a function that isn't pure in its
// implementation, it still expects a function to be pure in its type checking
// behavior, except for the special case of returning cty.DynamicPseudoType
// if it is not yet able to predict its return value based on current argument
// information.
func Unpredictable(f Function) Function {
	newSpec := *f.spec // shallow copy
	newSpec.Impl = unpredictableImpl
	return New(&newSpec)
}

func unpredictableImpl(args []cty.Value, retType cty.Type) (cty.Value, error) {
	return cty.UnknownVal(retType), nil
}
Commit	Line	Data
15c0b25d AP	1	package function
	2
	3	import (
	4	"github.com/zclconf/go-cty/cty"
	5	)
	6
	7	// Unpredictable wraps a given function such that it retains the same arguments
	8	// and type checking behavior but will return an unknown value when called.
	9	//
	10	// It is recommended that most functions be "pure", which is to say that they
	11	// will always produce the same value given particular input. However,
	12	// sometimes it is necessary to offer functions whose behavior depends on
	13	// some external state, such as reading a file or determining the current time.
	14	// In such cases, an unpredictable wrapper might be used to stand in for
	15	// the function during some sort of prior "checking" phase in order to delay
	16	// the actual effect until later.
	17	//
	18	// While Unpredictable can support a function that isn't pure in its
	19	// implementation, it still expects a function to be pure in its type checking
	20	// behavior, except for the special case of returning cty.DynamicPseudoType
	21	// if it is not yet able to predict its return value based on current argument
	22	// information.
	23	func Unpredictable(f Function) Function {
	24	newSpec := *f.spec // shallow copy
	25	newSpec.Impl = unpredictableImpl
	26	return New(&newSpec)
	27	}
	28
	29	func unpredictableImpl(args []cty.Value, retType cty.Type) (cty.Value, error) {
	30	return cty.UnknownVal(retType), nil
	31	}