github.com/avenga/couper@v1.12.2/eval/lib/default.go (about)

     1  package lib
     2  
     3  import (
     4  	"fmt"
     5  
     6  	"github.com/zclconf/go-cty/cty"
     7  	"github.com/zclconf/go-cty/cty/convert"
     8  	"github.com/zclconf/go-cty/cty/function"
     9  )
    10  
    11  var DefaultFunc = function.New(&function.Spec{
    12  	VarParam: &function.Parameter{
    13  		Name:             "vals",
    14  		Type:             cty.DynamicPseudoType,
    15  		AllowUnknown:     true,
    16  		AllowDynamicType: true,
    17  		AllowNull:        true,
    18  	},
    19  	Type: func(args []cty.Value) (cty.Type, error) {
    20  		var argTypes []cty.Type
    21  		for _, val := range args {
    22  			// ignore NilType values when determining the unsafe-unified return type
    23  			if val.Type() == cty.NilType {
    24  				continue
    25  			}
    26  			argTypes = append(argTypes, val.Type())
    27  		}
    28  		if len(argTypes) == 0 {
    29  			// no non-NilVal arguments
    30  			return cty.NilType, nil
    31  		}
    32  		retType, _ := convert.UnifyUnsafe(argTypes)
    33  		if retType == cty.NilType {
    34  			return cty.NilType, fmt.Errorf("all defined arguments must have the same type")
    35  		}
    36  		return retType, nil
    37  	},
    38  	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
    39  		for _, argVal := range args {
    40  			if !argVal.IsKnown() {
    41  				return cty.UnknownVal(retType), nil
    42  			}
    43  			if argVal.IsNull() || argVal.Type() == cty.NilType {
    44  				continue
    45  			}
    46  
    47  			// If the fallback type is a string and this argument too but an empty one, consider them as unset.
    48  			if argVal.Type() == cty.String && argVal.AsString() == "" && retType == cty.String {
    49  				continue
    50  			}
    51  
    52  			return convert.Convert(argVal, retType)
    53  		}
    54  		return args[len(args)-1], nil
    55  	},
    56  })