terraform: State.Add works with multiple resources [GH-7797]

terraform/state_add.go

@@ -151,6 +151,28 @@ func stateAddFunc_Resource_Module(
 }
 
 func stateAddFunc_Resource_Resource(s *State, fromAddr, addr *ResourceAddress, raw interface{}) error {
+	// raw can be either *ResourceState or []*ResourceState. The former means
+	// we're moving just one resource. The latter means we're moving a count
+	// of resources.
+	if list, ok := raw.([]*ResourceState); ok {
+		// We need at least one item
+		if len(list) == 0 {
+			return fmt.Errorf("resource move with no value to: %s", addr)
+		}
+
+		// Add each with a specific index
+		for i, rs := range list {
+			addrCopy := addr.Copy()
+			addrCopy.Index = i
+
+			if err := s.Add(fromAddr.String(), addrCopy.String(), rs); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+
 	src := raw.(*ResourceState).deepcopy()
 
 	// Initialize the resource
@@ -271,6 +293,8 @@ func detectValueAddLoc(raw interface{}) stateAddLoc {
 		return stateAddModule
 	case *ResourceState:
 		return stateAddResource
+	case []*ResourceState:
+		return stateAddResource
 	case *InstanceState:
 		return stateAddInstance
 	default:

terraform/state_add_test.go

@@ -371,6 +371,51 @@ func TestStateAdd(t *testing.T) {
 			},
 		},
 
+		"ResourceState with count unspecified => Resource Addr (new)": {
+			false,
+			"aws_instance.bar",
+			"aws_instance.foo",
+			[]*ResourceState{
+				&ResourceState{
+					Type: "test_instance",
+					Primary: &InstanceState{
+						ID: "foo",
+					},
+				},
+
+				&ResourceState{
+					Type: "test_instance",
+					Primary: &InstanceState{
+						ID: "bar",
+					},
+				},
+			},
+
+			&State{},
+			&State{
+				Modules: []*ModuleState{
+					&ModuleState{
+						Path: []string{"root"},
+						Resources: map[string]*ResourceState{
+							"aws_instance.foo.0": &ResourceState{
+								Type: "test_instance",
+								Primary: &InstanceState{
+									ID: "foo",
+								},
+							},
+
+							"aws_instance.foo.1": &ResourceState{
+								Type: "test_instance",
+								Primary: &InstanceState{
+									ID: "bar",
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+
 		"ResourceState => Resource Addr (existing)": {
 			true,
 			"aws_instance.bar",