bake: various fixes for composable attributes

This changes how the composable attributes are implemented and provides
various fixes to the first iteration.

Cache-from and cache-to now no longer print sensitive values that are
automatically added. These automatically added attributes are added when
the protobuf is created rather than at the time of parsing so they will
no longer be printed. If they are part of the original configuration
file, they will still be printed.

Empty strings will now be skipped. This was the original behavior and
composable attributes removed this functionality accidentally. This
functionality is now restored.

This also expands the available syntax that works with each of the
composable attributes. It is now possible to interleave the csv syntax
with the object syntax without any problems. The canonical form is still
the object syntax and variables are resolved according to that syntax.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

bake/hclparser/type_implied_ext.go

@@ -10,44 +10,60 @@ import (
 	"github.com/zclconf/go-cty/cty/gocty"
 )
 
-type CapsuleValue interface {
-	// FromCtyValue will initialize this value using a cty.Value.
-	FromCtyValue(in cty.Value, path cty.Path) error
-
+type ToCtyValueConverter interface {
 	// ToCtyValue will convert this capsule value into a native
 	// cty.Value. This should not return a capsule type.
 	ToCtyValue() cty.Value
 }
 
+type FromCtyValueConverter interface {
+	// FromCtyValue will initialize this value using a cty.Value.
+	FromCtyValue(in cty.Value, path cty.Path) error
+}
+
 type extensionType int
 
 const (
-	nativeTypeExtension extensionType = iota
+	unwrapCapsuleValueExtension extensionType = iota
 )
 
 func impliedTypeExt(rt reflect.Type, _ cty.Path) (cty.Type, error) {
-	if rt.AssignableTo(capsuleValueType) {
+	if rt.Kind() != reflect.Pointer {
+		rt = reflect.PointerTo(rt)
+	}
+
+	if isCapsuleType(rt) {
 		return capsuleValueCapsuleType(rt), nil
 	}
 	return cty.NilType, errdefs.ErrNotImplemented
 }
 
-var (
-	capsuleValueType  = reflect.TypeFor[CapsuleValue]()
-	capsuleValueTypes sync.Map
-)
+func isCapsuleType(rt reflect.Type) bool {
+	fromCtyValueType := reflect.TypeFor[FromCtyValueConverter]()
+	toCtyValueType := reflect.TypeFor[ToCtyValueConverter]()
+	return rt.Implements(fromCtyValueType) && rt.Implements(toCtyValueType)
+}
+
+var capsuleValueTypes sync.Map
 
 func capsuleValueCapsuleType(rt reflect.Type) cty.Type {
-	if val, loaded := capsuleValueTypes.Load(rt); loaded {
+	if rt.Kind() != reflect.Pointer {
+		panic("capsule value must be a pointer")
+	}
+
+	elem := rt.Elem()
+	if val, loaded := capsuleValueTypes.Load(elem); loaded {
 		return val.(cty.Type)
 	}
 
-	// First time used.
-	ety := cty.CapsuleWithOps(rt.Name(), rt.Elem(), &cty.CapsuleOps{
+	toCtyValueType := reflect.TypeFor[ToCtyValueConverter]()
+
+	// First time used. Initialize new capsule ops.
+	ops := &cty.CapsuleOps{
 		ConversionTo: func(_ cty.Type) func(cty.Value, cty.Path) (any, error) {
 			return func(in cty.Value, p cty.Path) (any, error) {
-				rv := reflect.New(rt.Elem()).Interface()
-				if err := rv.(CapsuleValue).FromCtyValue(in, p); err != nil {
+				rv := reflect.New(elem).Interface()
+				if err := rv.(FromCtyValueConverter).FromCtyValue(in, p); err != nil {
 					return nil, err
 				}
 				return rv, nil
@@ -55,30 +71,39 @@ func capsuleValueCapsuleType(rt reflect.Type) cty.Type {
 		},
 		ConversionFrom: func(want cty.Type) func(any, cty.Path) (cty.Value, error) {
 			return func(in any, _ cty.Path) (cty.Value, error) {
-				v := in.(CapsuleValue).ToCtyValue()
+				rv := reflect.ValueOf(in).Convert(toCtyValueType)
+				v := rv.Interface().(ToCtyValueConverter).ToCtyValue()
 				return convert.Convert(v, want)
 			}
 		},
 		ExtensionData: func(key any) any {
 			switch key {
-			case nativeTypeExtension:
-				zero := reflect.Zero(rt).Interface()
-				return zero.(CapsuleValue).ToCtyValue().Type()
-			default:
-				return nil
-			}
-		},
-	})
+			case unwrapCapsuleValueExtension:
+				zero := reflect.Zero(elem).Interface()
+				if conv, ok := zero.(ToCtyValueConverter); ok {
+					return conv.ToCtyValue().Type()
+				}
 
-	// Attempt to store the new type. Use whichever was loaded first in the case of a race condition.
-	val, _ := capsuleValueTypes.LoadOrStore(rt, ety)
+				zero = reflect.Zero(rt).Interface()
+				if conv, ok := zero.(ToCtyValueConverter); ok {
+					return conv.ToCtyValue().Type()
+				}
+			}
+			return nil
+		},
+	}
+
+	// Attempt to store the new type. Use whichever was loaded first in the case
+	// of a race condition.
+	ety := cty.CapsuleWithOps(elem.Name(), elem, ops)
+	val, _ := capsuleValueTypes.LoadOrStore(elem, ety)
 	return val.(cty.Type)
 }
 
-// ToNativeValue will convert a value to only native cty types which will
-// remove capsule types if possible.
-func ToNativeValue(in cty.Value) cty.Value {
-	want := toNativeType(in.Type())
+// UnwrapCtyValue will unwrap capsule type values into their native cty value
+// equivalents if possible.
+func UnwrapCtyValue(in cty.Value) cty.Value {
+	want := toCtyValueType(in.Type())
 	if in.Type().Equals(want) {
 		return in
 	} else if out, err := convert.Convert(in, want); err == nil {
@@ -87,17 +112,17 @@ func ToNativeValue(in cty.Value) cty.Value {
 	return cty.NullVal(want)
 }
 
-func toNativeType(in cty.Type) cty.Type {
+func toCtyValueType(in cty.Type) cty.Type {
 	if et := in.MapElementType(); et != nil {
-		return cty.Map(toNativeType(*et))
+		return cty.Map(toCtyValueType(*et))
 	}
 
 	if et := in.SetElementType(); et != nil {
-		return cty.Set(toNativeType(*et))
+		return cty.Set(toCtyValueType(*et))
 	}
 
 	if et := in.ListElementType(); et != nil {
-		return cty.List(toNativeType(*et))
+		return cty.List(toCtyValueType(*et))
 	}
 
 	if in.IsObjectType() {
@@ -105,7 +130,7 @@ func toNativeType(in cty.Type) cty.Type {
 		inAttrTypes := in.AttributeTypes()
 		outAttrTypes := make(map[string]cty.Type, len(inAttrTypes))
 		for name, typ := range inAttrTypes {
-			outAttrTypes[name] = toNativeType(typ)
+			outAttrTypes[name] = toCtyValueType(typ)
 			if in.AttributeOptional(name) {
 				optional = append(optional, name)
 			}
@@ -117,13 +142,13 @@ func toNativeType(in cty.Type) cty.Type {
 		inTypes := in.TupleElementTypes()
 		outTypes := make([]cty.Type, len(inTypes))
 		for i, typ := range inTypes {
-			outTypes[i] = toNativeType(typ)
+			outTypes[i] = toCtyValueType(typ)
 		}
 		return cty.Tuple(outTypes)
 	}
 
 	if in.IsCapsuleType() {
-		if out := in.CapsuleExtensionData(nativeTypeExtension); out != nil {
+		if out := in.CapsuleExtensionData(unwrapCapsuleValueExtension); out != nil {
 			return out.(cty.Type)
 		}
 		return cty.DynamicPseudoType
@@ -137,5 +162,5 @@ func ToCtyValue(val any, ty cty.Type) (cty.Value, error) {
 	if err != nil {
 		return out, err
 	}
-	return ToNativeValue(out), nil
+	return UnwrapCtyValue(out), nil
 }