From f51fb5e127a29e403d3afa6024d480e90205b831 Mon Sep 17 00:00:00 2001
From: Paul Hinze <paul@hashicorp.com>
Date: Thu, 26 Mar 2015 12:11:26 -0500
Subject: [PATCH] providers/aws: handle empty instancestate in state migration

fixes #1309
---
 .../aws/resource_aws_instance_migrate.go      |  6 ++++
 .../aws/resource_aws_instance_migrate_test.go | 24 ++++++++++++++++
 terraform/state.go                            |  4 +++
 terraform/state_test.go                       | 28 +++++++++++++++++++
 4 files changed, 62 insertions(+)

diff --git a/builtin/providers/aws/resource_aws_instance_migrate.go b/builtin/providers/aws/resource_aws_instance_migrate.go
index adb7a01ec..5d7075f75 100644
--- a/builtin/providers/aws/resource_aws_instance_migrate.go
+++ b/builtin/providers/aws/resource_aws_instance_migrate.go
@@ -24,7 +24,13 @@ func resourceAwsInstanceMigrateState(
 }
 
 func migrateStateV0toV1(is *terraform.InstanceState) (*terraform.InstanceState, error) {
+	if is.Empty() {
+		log.Println("[DEBUG] Empty InstanceState; nothing to migrate.")
+		return is, nil
+	}
+
 	log.Printf("[DEBUG] Attributes before migration: %#v", is.Attributes)
+
 	// Delete old count
 	delete(is.Attributes, "block_device.#")
 
diff --git a/builtin/providers/aws/resource_aws_instance_migrate_test.go b/builtin/providers/aws/resource_aws_instance_migrate_test.go
index 5738f2508..d39294331 100644
--- a/builtin/providers/aws/resource_aws_instance_migrate_test.go
+++ b/builtin/providers/aws/resource_aws_instance_migrate_test.go
@@ -115,6 +115,7 @@ func TestAWSInstanceMigrateState(t *testing.T) {
 
 	for tn, tc := range cases {
 		is := &terraform.InstanceState{
+			ID:         "i-abc123",
 			Attributes: tc.Attributes,
 		}
 		is, err := resourceAwsInstanceMigrateState(
@@ -133,3 +134,26 @@ func TestAWSInstanceMigrateState(t *testing.T) {
 		}
 	}
 }
+
+func TestAWSInstanceMigrateState_empty(t *testing.T) {
+	var is *terraform.InstanceState
+	var meta interface{}
+
+	// should handle nil
+	is, err := resourceAwsInstanceMigrateState(0, is, meta)
+
+	if err != nil {
+		t.Fatalf("err: %#v", err)
+	}
+	if is != nil {
+		t.Fatalf("expected nil instancestate, got: %#v", is)
+	}
+
+	// should handle non-nil but empty
+	is = &terraform.InstanceState{}
+	is, err = resourceAwsInstanceMigrateState(0, is, meta)
+
+	if err != nil {
+		t.Fatalf("err: %#v", err)
+	}
+}
diff --git a/terraform/state.go b/terraform/state.go
index 1a1a28bea..d4341302d 100644
--- a/terraform/state.go
+++ b/terraform/state.go
@@ -885,6 +885,10 @@ func (i *InstanceState) deepcopy() *InstanceState {
 	return n
 }
 
+func (s *InstanceState) Empty() bool {
+	return s == nil || s.ID == ""
+}
+
 func (s *InstanceState) Equal(other *InstanceState) bool {
 	// Short circuit some nil checks
 	if s == nil || other == nil {
diff --git a/terraform/state_test.go b/terraform/state_test.go
index e222b1b72..7f3dbb567 100644
--- a/terraform/state_test.go
+++ b/terraform/state_test.go
@@ -366,6 +366,34 @@ func TestResourceStateTaint(t *testing.T) {
 	}
 }
 
+func TestInstanceStateEmpty(t *testing.T) {
+	cases := map[string]struct {
+		In     *InstanceState
+		Result bool
+	}{
+		"nil is empty": {
+			nil,
+			true,
+		},
+		"non-nil but without ID is empty": {
+			&InstanceState{},
+			true,
+		},
+		"with ID is not empty": {
+			&InstanceState{
+				ID: "i-abc123",
+			},
+			false,
+		},
+	}
+
+	for tn, tc := range cases {
+		if tc.In.Empty() != tc.Result {
+			t.Fatalf("%q expected %#v to be empty: %#v", tn, tc.In, tc.Result)
+		}
+	}
+}
+
 func TestInstanceStateEqual(t *testing.T) {
 	cases := []struct {
 		Result   bool