core: Fix interpolation of complex structures

This commit makes two changes: map interpolation can now read flatmapped
structures, such as those present in remote state outputs, and lists are
sorted by the index instead of the value.

terraform/interpolate.go

@@ -13,6 +13,7 @@ import (
 	"github.com/hashicorp/hil/ast"
 	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/flatmap"
 )
 
 const (
@@ -213,6 +214,7 @@ func (i *Interpolater) valueResourceVar(
 	result map[string]ast.Variable) error {
 	// If we're computing all dynamic fields, then module vars count
 	// and we mark it as computed.
+
 	if i.Operation == walkValidate {
 		result[n] = ast.Variable{
 			Value: config.UnknownVariableValue,
@@ -343,6 +345,7 @@ func (i *Interpolater) valueUserVar(
 func (i *Interpolater) computeResourceVariable(
 	scope *InterpolationScope,
 	v *config.ResourceVariable) (*ast.Variable, error) {
+
 	id := v.ResourceId()
 	if v.Multi {
 		id = fmt.Sprintf("%s.%d", id, v.Index)
@@ -589,21 +592,19 @@ func (i *Interpolater) interpolateComplexTypeAttribute(
 			return unknownVariable(), nil
 		}
 
-		var keys []string
+		keys := make([]string, 0)
 		listElementKey := regexp.MustCompile("^" + resourceID + "\\.[0-9]+$")
 		for id, _ := range attributes {
 			if listElementKey.MatchString(id) {
 				keys = append(keys, id)
 			}
 		}
+		sort.Strings(keys)
 
 		var members []string
 		for _, key := range keys {
 			members = append(members, attributes[key])
 		}
-		// This behaviour still seems very broken to me... it retains BC but is
-		// probably going to cause problems in future
-		sort.Strings(members)
 
 		return hil.InterfaceToVariable(members)
 	}
@@ -620,19 +621,16 @@ func (i *Interpolater) interpolateComplexTypeAttribute(
 			return unknownVariable(), nil
 		}
 
-		var keys []string
+		resourceFlatMap := make(map[string]string)
 		mapElementKey := regexp.MustCompile("^" + resourceID + "\\.([^%]+)$")
-		for id, _ := range attributes {
-			if submatches := mapElementKey.FindAllStringSubmatch(id, -1); len(submatches) > 0 {
-				keys = append(keys, submatches[0][1])
+		for id, val := range attributes {
+			if mapElementKey.MatchString(id) {
+				resourceFlatMap[id] = val
 			}
 		}
 
-		members := make(map[string]interface{})
-		for _, key := range keys {
-			members[key] = attributes[resourceID+"."+key]
-		}
-		return hil.InterfaceToVariable(members)
+		expanded := flatmap.Expand(resourceFlatMap, resourceID)
+		return hil.InterfaceToVariable(expanded)
 	}
 
 	return ast.Variable{}, fmt.Errorf("No complex type %s found", resourceID)

terraform/interpolate_test.go

@@ -278,10 +278,10 @@ func TestInterpolator_resourceMultiAttributes(t *testing.T) {
 	lock := new(sync.RWMutex)
 	state := &State{
 		Modules: []*ModuleState{
-			&ModuleState{
+			{
 				Path: rootModulePath,
 				Resources: map[string]*ResourceState{
-					"aws_route53_zone.yada": &ResourceState{
+					"aws_route53_zone.yada": {
 						Type:         "aws_route53_zone",
 						Dependencies: []string{},
 						Primary: &InstanceState{
@@ -354,8 +354,8 @@ func TestInterpolator_resourceMultiAttributesWithResourceCount(t *testing.T) {
 		"ns-601.awsdns-11.net",
 		"ns-000.awsdns-38.org",
 		"ns-444.awsdns-18.co.uk",
-		"ns-666.awsdns-11.net",
 		"ns-999.awsdns-62.com",
+		"ns-666.awsdns-11.net",
 	}
 
 	// More than 1 element