| package convert |
| |
| import ( |
| "errors" |
| |
| "github.com/zclconf/go-cty/cty" |
| ) |
| |
| // This file contains the public interface of this package, which is intended |
| // to be a small, convenient interface designed for easy integration into |
| // a hypothetical language type checker and interpreter. |
| |
| // Conversion is a named function type representing a conversion from a |
| // value of one type to a value of another type. |
| // |
| // The source type for a conversion is always the source type given to |
| // the function that returned the Conversion, but there is no way to recover |
| // that from a Conversion value itself. If a Conversion is given a value |
| // that is not of its expected type (with the exception of DynamicPseudoType, |
| // which is always supported) then the function may panic or produce undefined |
| // results. |
| type Conversion func(in cty.Value) (out cty.Value, err error) |
| |
| // GetConversion returns a Conversion between the given in and out Types if |
| // a safe one is available, or returns nil otherwise. |
| func GetConversion(in cty.Type, out cty.Type) Conversion { |
| return retConversion(getConversion(in, out, false)) |
| } |
| |
| // GetConversionUnsafe returns a Conversion between the given in and out Types |
| // if either a safe or unsafe one is available, or returns nil otherwise. |
| func GetConversionUnsafe(in cty.Type, out cty.Type) Conversion { |
| return retConversion(getConversion(in, out, true)) |
| } |
| |
| // Convert returns the result of converting the given value to the given type |
| // if an safe or unsafe conversion is available, or returns an error if such a |
| // conversion is impossible. |
| // |
| // This is a convenience wrapper around calling GetConversionUnsafe and then |
| // immediately passing the given value to the resulting function. |
| func Convert(in cty.Value, want cty.Type) (cty.Value, error) { |
| if in.Type().Equals(want) { |
| return in, nil |
| } |
| |
| conv := GetConversionUnsafe(in.Type(), want) |
| if conv == nil { |
| return cty.NilVal, errors.New(MismatchMessage(in.Type(), want)) |
| } |
| return conv(in) |
| } |
| |
| // Unify attempts to find the most general type that can be converted from |
| // all of the given types. If this is possible, that type is returned along |
| // with a slice of necessary conversions for some of the given types. |
| // |
| // If no common supertype can be found, this function returns cty.NilType and |
| // a nil slice. |
| // |
| // If a common supertype *can* be found, the returned slice will always be |
| // non-nil and will contain a non-nil conversion for each given type that |
| // needs to be converted, with indices corresponding to the input slice. |
| // Any given type that does *not* need conversion (because it is already of |
| // the appropriate type) will have a nil Conversion. |
| // |
| // cty.DynamicPseudoType is, as usual, a special case. If the given type list |
| // contains a mixture of dynamic and non-dynamic types, the dynamic types are |
| // disregarded for type selection and a conversion is returned for them that |
| // will attempt a late conversion of the given value to the target type, |
| // failing with a conversion error if the eventual concrete type is not |
| // compatible. If *all* given types are DynamicPseudoType, or in the |
| // degenerate case of an empty slice of types, the returned type is itself |
| // cty.DynamicPseudoType and no conversions are attempted. |
| func Unify(types []cty.Type) (cty.Type, []Conversion) { |
| return unify(types, false) |
| } |
| |
| // UnifyUnsafe is the same as Unify except that it may return unsafe |
| // conversions in situations where a safe conversion isn't also available. |
| func UnifyUnsafe(types []cty.Type) (cty.Type, []Conversion) { |
| return unify(types, true) |
| } |