terraform: ResourceConfig.DeepCopy

This implements DeepCopy, still need to implement Equals to make this
more useful. Coming in the next commit but this still has its own full
functionality + tests.

terraform/resource.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/hashicorp/terraform/config"
+	"github.com/mitchellh/copystructure"
 )
 
 // ResourceProvisionerConfig is used to pair a provisioner
@@ -93,6 +94,25 @@ func NewResourceConfig(c *config.RawConfig) *ResourceConfig {
 	return result
 }
 
+// DeepCopy performs a deep copy of the configuration. This makes it safe
+// to modify any of the structures that are part of the resource config without
+// affecting the original configuration.
+func (c *ResourceConfig) DeepCopy() *ResourceConfig {
+	// Copy, this will copy all the exported attributes
+	copy, err := copystructure.Config{Lock: true}.Copy(c)
+	if err != nil {
+		panic(err)
+	}
+
+	// Force the type
+	result := copy.(*ResourceConfig)
+
+	// For the raw configuration, we can just use its own copy method
+	result.raw = c.raw.Copy()
+
+	return result
+}
+
 // CheckSet checks that the given list of configuration keys is
 // properly set. If not, errors are returned for each unset key.
 //

terraform/resource_test.go

@@ -1,6 +1,7 @@
 package terraform
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 
@@ -212,6 +213,19 @@ func TestResourceConfigGet(t *testing.T) {
 		if !reflect.DeepEqual(v, tc.Value) {
 			t.Fatalf("%d bad: %#v", i, v)
 		}
+
+		// If we have vars, we don't test copying
+		if len(tc.Vars) > 0 {
+			continue
+		}
+
+		// Test copying
+		t.Run(fmt.Sprintf("copy-%d", i), func(t *testing.T) {
+			copy := rc.DeepCopy()
+			if !reflect.DeepEqual(copy, rc) {
+				t.Fatalf("bad:\n\n%#v\n\n%#v", copy, rc)
+			}
+		})
 	}
 }