terraform/lang/funcs/collection.go

121 lines
3.7 KiB
Go

package funcs
import (
"fmt"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/function"
"github.com/zclconf/go-cty/cty/function/stdlib"
"github.com/zclconf/go-cty/cty/gocty"
)
var ElementFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "list",
Type: cty.DynamicPseudoType,
},
{
Name: "index",
Type: cty.Number,
},
},
Type: func(args []cty.Value) (cty.Type, error) {
list := args[0]
listTy := list.Type()
switch {
case listTy.IsListType():
return listTy.ElementType(), nil
case listTy.IsTupleType():
etys := listTy.TupleElementTypes()
var index int
err := gocty.FromCtyValue(args[1], &index)
if err != nil {
// e.g. fractional number where whole number is required
return cty.DynamicPseudoType, fmt.Errorf("invalid index: %s", err)
}
if len(etys) == 0 {
return cty.DynamicPseudoType, fmt.Errorf("cannot use element function with an empty list")
}
index = index % len(etys)
return etys[index], nil
default:
return cty.DynamicPseudoType, fmt.Errorf("cannot read elements from %s", listTy.FriendlyName())
}
},
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
var index int
err := gocty.FromCtyValue(args[1], &index)
if err != nil {
// can't happen because we checked this in the Type function above
return cty.DynamicVal, fmt.Errorf("invalid index: %s", err)
}
l := args[0].LengthInt()
if l == 0 {
return cty.DynamicVal, fmt.Errorf("cannot use element function with an empty list")
}
index = index % l
// We did all the necessary type checks in the type function above,
// so this is guaranteed not to fail.
return args[0].Index(cty.NumberIntVal(int64(index))), nil
},
})
var LengthFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "value",
Type: cty.DynamicPseudoType,
AllowDynamicType: true,
AllowUnknown: true,
},
},
Type: func(args []cty.Value) (cty.Type, error) {
collTy := args[0].Type()
switch {
case collTy == cty.String || collTy.IsTupleType() || collTy.IsListType() || collTy.IsMapType() || collTy.IsSetType() || collTy == cty.DynamicPseudoType:
return cty.Number, nil
default:
return cty.Number, fmt.Errorf("argument must be a string, a collection type, or a structural type")
}
},
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
coll := args[0]
collTy := args[0].Type()
switch {
case collTy == cty.DynamicPseudoType:
return cty.UnknownVal(cty.Number), nil
case collTy.IsTupleType():
l := len(collTy.TupleElementTypes())
return cty.NumberIntVal(int64(l)), nil
case collTy.IsObjectType():
l := len(collTy.AttributeTypes())
return cty.NumberIntVal(int64(l)), nil
case collTy == cty.String:
// We'll delegate to the cty stdlib strlen function here, because
// it deals with all of the complexities of tokenizing unicode
// grapheme clusters.
return stdlib.Strlen(coll)
case collTy.IsListType() || collTy.IsSetType() || collTy.IsMapType():
return coll.Length(), nil
default:
// Should never happen, because of the checks in our Type func above
return cty.UnknownVal(cty.Number), fmt.Errorf("impossible value type for length(...)")
}
},
})
// Element returns a single element from a given list at the given index. If
// index is greater than the length of the list then it is wrapped modulo
// the list length.
func Element(list, index cty.Value) (cty.Value, error) {
return ElementFunc.Call([]cty.Value{list, index})
}
// Length returns the number of elements in the given collection or number of
// Unicode characters in the given string.
func Length(collection cty.Value) (cty.Value, error) {
return LengthFunc.Call([]cty.Value{collection})
}