358 lines
11 KiB
Go
358 lines
11 KiB
Go
package convert
|
|
|
|
import (
|
|
"github.com/zclconf/go-cty/cty"
|
|
)
|
|
|
|
// The current unify implementation is somewhat inefficient, but we accept this
|
|
// under the assumption that it will generally be used with small numbers of
|
|
// types and with types of reasonable complexity. However, it does have a
|
|
// "happy path" where all of the given types are equal.
|
|
//
|
|
// This function is likely to have poor performance in cases where any given
|
|
// types are very complex (lots of deeply-nested structures) or if the list
|
|
// of types itself is very large. In particular, it will walk the nested type
|
|
// structure under the given types several times, especially when given a
|
|
// list of types for which unification is not possible, since each permutation
|
|
// will be tried to determine that result.
|
|
func unify(types []cty.Type, unsafe bool) (cty.Type, []Conversion) {
|
|
if len(types) == 0 {
|
|
// Degenerate case
|
|
return cty.NilType, nil
|
|
}
|
|
|
|
// If all of the given types are of the same structural kind, we may be
|
|
// able to construct a new type that they can all be unified to, even if
|
|
// that is not one of the given types. We must try this before the general
|
|
// behavior below because in unsafe mode we can convert an object type to
|
|
// a subset of that type, which would be a much less useful conversion for
|
|
// unification purposes.
|
|
{
|
|
mapCt := 0
|
|
objectCt := 0
|
|
tupleCt := 0
|
|
dynamicCt := 0
|
|
for _, ty := range types {
|
|
switch {
|
|
case ty.IsMapType():
|
|
mapCt++
|
|
case ty.IsObjectType():
|
|
objectCt++
|
|
case ty.IsTupleType():
|
|
tupleCt++
|
|
case ty == cty.DynamicPseudoType:
|
|
dynamicCt++
|
|
default:
|
|
break
|
|
}
|
|
}
|
|
switch {
|
|
case mapCt > 0 && (mapCt+dynamicCt) == len(types):
|
|
return unifyMapTypes(types, unsafe, dynamicCt > 0)
|
|
case objectCt > 0 && (objectCt+dynamicCt) == len(types):
|
|
return unifyObjectTypes(types, unsafe, dynamicCt > 0)
|
|
case tupleCt > 0 && (tupleCt+dynamicCt) == len(types):
|
|
return unifyTupleTypes(types, unsafe, dynamicCt > 0)
|
|
case objectCt > 0 && tupleCt > 0:
|
|
// Can never unify object and tuple types since they have incompatible kinds
|
|
return cty.NilType, nil
|
|
}
|
|
}
|
|
|
|
prefOrder := sortTypes(types)
|
|
|
|
// sortTypes gives us an order where earlier items are preferable as
|
|
// our result type. We'll now walk through these and choose the first
|
|
// one we encounter for which conversions exist for all source types.
|
|
conversions := make([]Conversion, len(types))
|
|
Preferences:
|
|
for _, wantTypeIdx := range prefOrder {
|
|
wantType := types[wantTypeIdx]
|
|
for i, tryType := range types {
|
|
if i == wantTypeIdx {
|
|
// Don't need to convert our wanted type to itself
|
|
conversions[i] = nil
|
|
continue
|
|
}
|
|
|
|
if tryType.Equals(wantType) {
|
|
conversions[i] = nil
|
|
continue
|
|
}
|
|
|
|
if unsafe {
|
|
conversions[i] = GetConversionUnsafe(tryType, wantType)
|
|
} else {
|
|
conversions[i] = GetConversion(tryType, wantType)
|
|
}
|
|
|
|
if conversions[i] == nil {
|
|
// wantType is not a suitable unification type, so we'll
|
|
// try the next one in our preference order.
|
|
continue Preferences
|
|
}
|
|
}
|
|
|
|
return wantType, conversions
|
|
}
|
|
|
|
// If we fall out here, no unification is possible
|
|
return cty.NilType, nil
|
|
}
|
|
|
|
func unifyMapTypes(types []cty.Type, unsafe bool, hasDynamic bool) (cty.Type, []Conversion) {
|
|
// If we had any dynamic types in the input here then we can't predict
|
|
// what path we'll take through here once these become known types, so
|
|
// we'll conservatively produce DynamicVal for these.
|
|
if hasDynamic {
|
|
return unifyAllAsDynamic(types)
|
|
}
|
|
|
|
elemTypes := make([]cty.Type, 0, len(types))
|
|
for _, ty := range types {
|
|
elemTypes = append(elemTypes, ty.ElementType())
|
|
}
|
|
retElemType, _ := unify(elemTypes, unsafe)
|
|
if retElemType == cty.NilType {
|
|
return cty.NilType, nil
|
|
}
|
|
|
|
retTy := cty.Map(retElemType)
|
|
|
|
conversions := make([]Conversion, len(types))
|
|
for i, ty := range types {
|
|
if ty.Equals(retTy) {
|
|
continue
|
|
}
|
|
if unsafe {
|
|
conversions[i] = GetConversionUnsafe(ty, retTy)
|
|
} else {
|
|
conversions[i] = GetConversion(ty, retTy)
|
|
}
|
|
if conversions[i] == nil {
|
|
// Shouldn't be reachable, since we were able to unify
|
|
return cty.NilType, nil
|
|
}
|
|
}
|
|
|
|
return retTy, conversions
|
|
}
|
|
|
|
func unifyObjectTypes(types []cty.Type, unsafe bool, hasDynamic bool) (cty.Type, []Conversion) {
|
|
// If we had any dynamic types in the input here then we can't predict
|
|
// what path we'll take through here once these become known types, so
|
|
// we'll conservatively produce DynamicVal for these.
|
|
if hasDynamic {
|
|
return unifyAllAsDynamic(types)
|
|
}
|
|
|
|
// There are two different ways we can succeed here:
|
|
// - If all of the given object types have the same set of attribute names
|
|
// and the corresponding types are all unifyable, then we construct that
|
|
// type.
|
|
// - If the given object types have different attribute names or their
|
|
// corresponding types are not unifyable, we'll instead try to unify
|
|
// all of the attribute types together to produce a map type.
|
|
//
|
|
// Our unification behavior is intentionally stricter than our conversion
|
|
// behavior for subset object types because user intent is different with
|
|
// unification use-cases: it makes sense to allow {"foo":true} to convert
|
|
// to emptyobjectval, but unifying an object with an attribute with the
|
|
// empty object type should be an error because unifying to the empty
|
|
// object type would be suprising and useless.
|
|
|
|
firstAttrs := types[0].AttributeTypes()
|
|
for _, ty := range types[1:] {
|
|
thisAttrs := ty.AttributeTypes()
|
|
if len(thisAttrs) != len(firstAttrs) {
|
|
// If number of attributes is different then there can be no
|
|
// object type in common.
|
|
return unifyObjectTypesToMap(types, unsafe)
|
|
}
|
|
for name := range thisAttrs {
|
|
if _, ok := firstAttrs[name]; !ok {
|
|
// If attribute names don't exactly match then there can be
|
|
// no object type in common.
|
|
return unifyObjectTypesToMap(types, unsafe)
|
|
}
|
|
}
|
|
}
|
|
|
|
// If we get here then we've proven that all of the given object types
|
|
// have exactly the same set of attribute names, though the types may
|
|
// differ.
|
|
retAtys := make(map[string]cty.Type)
|
|
atysAcross := make([]cty.Type, len(types))
|
|
for name := range firstAttrs {
|
|
for i, ty := range types {
|
|
atysAcross[i] = ty.AttributeType(name)
|
|
}
|
|
retAtys[name], _ = unify(atysAcross, unsafe)
|
|
if retAtys[name] == cty.NilType {
|
|
// Cannot unify this attribute alone, which means that unification
|
|
// of everything down to a map type can't be possible either.
|
|
return cty.NilType, nil
|
|
}
|
|
}
|
|
retTy := cty.Object(retAtys)
|
|
|
|
conversions := make([]Conversion, len(types))
|
|
for i, ty := range types {
|
|
if ty.Equals(retTy) {
|
|
continue
|
|
}
|
|
if unsafe {
|
|
conversions[i] = GetConversionUnsafe(ty, retTy)
|
|
} else {
|
|
conversions[i] = GetConversion(ty, retTy)
|
|
}
|
|
if conversions[i] == nil {
|
|
// Shouldn't be reachable, since we were able to unify
|
|
return unifyObjectTypesToMap(types, unsafe)
|
|
}
|
|
}
|
|
|
|
return retTy, conversions
|
|
}
|
|
|
|
func unifyObjectTypesToMap(types []cty.Type, unsafe bool) (cty.Type, []Conversion) {
|
|
// This is our fallback case for unifyObjectTypes, where we see if we can
|
|
// construct a map type that can accept all of the attribute types.
|
|
|
|
var atys []cty.Type
|
|
for _, ty := range types {
|
|
for _, aty := range ty.AttributeTypes() {
|
|
atys = append(atys, aty)
|
|
}
|
|
}
|
|
|
|
ety, _ := unify(atys, unsafe)
|
|
if ety == cty.NilType {
|
|
return cty.NilType, nil
|
|
}
|
|
|
|
retTy := cty.Map(ety)
|
|
conversions := make([]Conversion, len(types))
|
|
for i, ty := range types {
|
|
if ty.Equals(retTy) {
|
|
continue
|
|
}
|
|
if unsafe {
|
|
conversions[i] = GetConversionUnsafe(ty, retTy)
|
|
} else {
|
|
conversions[i] = GetConversion(ty, retTy)
|
|
}
|
|
if conversions[i] == nil {
|
|
return cty.NilType, nil
|
|
}
|
|
}
|
|
return retTy, conversions
|
|
}
|
|
|
|
func unifyTupleTypes(types []cty.Type, unsafe bool, hasDynamic bool) (cty.Type, []Conversion) {
|
|
// If we had any dynamic types in the input here then we can't predict
|
|
// what path we'll take through here once these become known types, so
|
|
// we'll conservatively produce DynamicVal for these.
|
|
if hasDynamic {
|
|
return unifyAllAsDynamic(types)
|
|
}
|
|
|
|
// There are two different ways we can succeed here:
|
|
// - If all of the given tuple types have the same sequence of element types
|
|
// and the corresponding types are all unifyable, then we construct that
|
|
// type.
|
|
// - If the given tuple types have different element types or their
|
|
// corresponding types are not unifyable, we'll instead try to unify
|
|
// all of the elements types together to produce a list type.
|
|
|
|
firstEtys := types[0].TupleElementTypes()
|
|
for _, ty := range types[1:] {
|
|
thisEtys := ty.TupleElementTypes()
|
|
if len(thisEtys) != len(firstEtys) {
|
|
// If number of elements is different then there can be no
|
|
// tuple type in common.
|
|
return unifyTupleTypesToList(types, unsafe)
|
|
}
|
|
}
|
|
|
|
// If we get here then we've proven that all of the given tuple types
|
|
// have the same number of elements, though the types may differ.
|
|
retEtys := make([]cty.Type, len(firstEtys))
|
|
atysAcross := make([]cty.Type, len(types))
|
|
for idx := range firstEtys {
|
|
for tyI, ty := range types {
|
|
atysAcross[tyI] = ty.TupleElementTypes()[idx]
|
|
}
|
|
retEtys[idx], _ = unify(atysAcross, unsafe)
|
|
if retEtys[idx] == cty.NilType {
|
|
// Cannot unify this element alone, which means that unification
|
|
// of everything down to a map type can't be possible either.
|
|
return cty.NilType, nil
|
|
}
|
|
}
|
|
retTy := cty.Tuple(retEtys)
|
|
|
|
conversions := make([]Conversion, len(types))
|
|
for i, ty := range types {
|
|
if ty.Equals(retTy) {
|
|
continue
|
|
}
|
|
if unsafe {
|
|
conversions[i] = GetConversionUnsafe(ty, retTy)
|
|
} else {
|
|
conversions[i] = GetConversion(ty, retTy)
|
|
}
|
|
if conversions[i] == nil {
|
|
// Shouldn't be reachable, since we were able to unify
|
|
return unifyTupleTypesToList(types, unsafe)
|
|
}
|
|
}
|
|
|
|
return retTy, conversions
|
|
}
|
|
|
|
func unifyTupleTypesToList(types []cty.Type, unsafe bool) (cty.Type, []Conversion) {
|
|
// This is our fallback case for unifyTupleTypes, where we see if we can
|
|
// construct a list type that can accept all of the element types.
|
|
|
|
var etys []cty.Type
|
|
for _, ty := range types {
|
|
for _, ety := range ty.TupleElementTypes() {
|
|
etys = append(etys, ety)
|
|
}
|
|
}
|
|
|
|
ety, _ := unify(etys, unsafe)
|
|
if ety == cty.NilType {
|
|
return cty.NilType, nil
|
|
}
|
|
|
|
retTy := cty.List(ety)
|
|
conversions := make([]Conversion, len(types))
|
|
for i, ty := range types {
|
|
if ty.Equals(retTy) {
|
|
continue
|
|
}
|
|
if unsafe {
|
|
conversions[i] = GetConversionUnsafe(ty, retTy)
|
|
} else {
|
|
conversions[i] = GetConversion(ty, retTy)
|
|
}
|
|
if conversions[i] == nil {
|
|
// Shouldn't be reachable, since we were able to unify
|
|
return unifyObjectTypesToMap(types, unsafe)
|
|
}
|
|
}
|
|
return retTy, conversions
|
|
}
|
|
|
|
func unifyAllAsDynamic(types []cty.Type) (cty.Type, []Conversion) {
|
|
conversions := make([]Conversion, len(types))
|
|
for i := range conversions {
|
|
conversions[i] = func(cty.Value) (cty.Value, error) {
|
|
return cty.DynamicVal, nil
|
|
}
|
|
}
|
|
return cty.DynamicPseudoType, conversions
|
|
}
|