terraform: ResourceConfig.DeepCopy should handle the nil case

terraform/resource.go

@@ -98,6 +98,11 @@ func NewResourceConfig(c *config.RawConfig) *ResourceConfig {
 // to modify any of the structures that are part of the resource config without
 // affecting the original configuration.
 func (c *ResourceConfig) DeepCopy() *ResourceConfig {
+	// DeepCopying a nil should return a nil to avoid panics
+	if c == nil {
+		return nil
+	}
+
 	// Copy, this will copy all the exported attributes
 	copy, err := copystructure.Config{Lock: true}.Copy(c)
 	if err != nil {

terraform/resource_test.go

@@ -239,6 +239,14 @@ func TestResourceConfigGet(t *testing.T) {
 	}
 }
 
+func TestResourceConfigDeepCopy_nil(t *testing.T) {
+	var nilRc *ResourceConfig
+	actual := nilRc.DeepCopy()
+	if actual != nil {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
 func TestResourceConfigEqual_nil(t *testing.T) {
 	var nilRc *ResourceConfig
 	notNil := NewResourceConfig(nil)