config: Support create_before_destroy config

config/config.go

@@ -54,12 +54,13 @@ type ProviderConfig struct {
 // A Terraform resource is something that represents some component that
 // can be created and managed, and has some properties associated with it.
 type Resource struct {
-	Name         string
-	Type         string
-	Count        int
-	RawConfig    *RawConfig
-	Provisioners []*Provisioner
-	DependsOn    []string
+	Name                string
+	Type                string
+	Count               int
+	RawConfig           *RawConfig
+	Provisioners        []*Provisioner
+	DependsOn           []string
+	CreateBeforeDestroy bool
 }
 
 // Provisioner is a configured provisioner step on a resource.

config/loader_hcl.go

@@ -394,6 +394,7 @@ func loadResourcesHcl(os *hclobj.Object) ([]*Resource, error) {
 			delete(config, "count")
 			delete(config, "depends_on")
 			delete(config, "provisioner")
+			delete(config, "create_before_destroy")
 
 			rawConfig, err := NewRawConfig(config)
 			if err != nil {
@@ -457,13 +458,28 @@ func loadResourcesHcl(os *hclobj.Object) ([]*Resource, error) {
 				}
 			}
 
+			// Check if the resource should be re-created before
+			// destroying the existing instance
+			var createBeforeDestroy bool
+			if o := obj.Get("create_before_destroy", false); o != nil {
+				err = hcl.DecodeObject(&createBeforeDestroy, o)
+				if err != nil {
+					return nil, fmt.Errorf(
+						"Error parsing create_before_destroy for %s[%s]: %s",
+						t.Key,
+						k,
+						err)
+				}
+			}
+
 			result = append(result, &Resource{
-				Name:         k,
-				Type:         t.Key,
-				Count:        count,
-				RawConfig:    rawConfig,
-				Provisioners: provisioners,
-				DependsOn:    dependsOn,
+				Name:                k,
+				Type:                t.Key,
+				Count:               count,
+				RawConfig:           rawConfig,
+				Provisioners:        provisioners,
+				DependsOn:           dependsOn,
+				CreateBeforeDestroy: createBeforeDestroy,
 			})
 		}
 	}

config/loader_test.go

@@ -346,6 +346,43 @@ func TestLoad_connections(t *testing.T) {
 	}
 }
 
+func TestLoad_createBeforeDestroy(t *testing.T) {
+	c, err := Load(filepath.Join(fixtureDir, "create-before-destroy.tf"))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if c == nil {
+		t.Fatal("config should not be nil")
+	}
+
+	actual := resourcesStr(c.Resources)
+	if actual != strings.TrimSpace(createBeforeDestroyResourcesStr) {
+		t.Fatalf("bad:\n%s", actual)
+	}
+
+	// Check for the flag value
+	r := c.Resources[0]
+	if r.Name != "web" && r.Type != "aws_instance" {
+		t.Fatalf("Bad: %#v", r)
+	}
+
+	// Should enable create before destroy
+	if !r.CreateBeforeDestroy {
+		t.Fatalf("Bad: %#v", r)
+	}
+
+	r = c.Resources[1]
+	if r.Name != "bar" && r.Type != "aws_instance" {
+		t.Fatalf("Bad: %#v", r)
+	}
+
+	// Should not enable create before destroy
+	if r.CreateBeforeDestroy {
+		t.Fatalf("Bad: %#v", r)
+	}
+}
+
 const basicOutputsStr = `
 web_ip
   vars
@@ -523,3 +560,10 @@ foo (required)
   <>
   <>
 `
+
+const createBeforeDestroyResourcesStr = `
+aws_instance[bar] (x1)
+  ami
+aws_instance[web] (x1)
+  ami
+`

config/test-fixtures/create-before-destroy.tf

@@ -0,0 +1,10 @@
+
+resource "aws_instance" "web" {
+    ami = "foo"
+    create_before_destroy = true
+}
+
+resource "aws_instance" "bar" {
+    ami = "foo"
+    create_before_destroy = false
+}