packer-cn/hcl2template/function/length.go

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package function
import (
"errors"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/function"
"github.com/zclconf/go-cty/cty/function/stdlib"
)
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.IsObjectType() || collTy.IsListType() || collTy.IsMapType() || collTy.IsSetType() || collTy == cty.DynamicPseudoType:
return cty.Number, nil
default:
return cty.Number, errors.New("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), errors.New("impossible value type for length(...)")
}
},
})