From efe754183b70f06e2d7216042267089c80ab3459 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Wed, 15 Feb 2017 14:20:59 -0800
Subject: [PATCH 1/3] state/remote: export ClientLocker, test for
 implementation

This adds unit tests (that will fail at compile time) if various structs
don't implement the right interfaces for locking
---
 backend/remote-state/consul/client_test.go |  1 +
 state/backup_test.go                       |  4 ++++
 state/remote/remote.go                     | 11 +++++++++++
 state/remote/state.go                      | 22 ++++++++--------------
 state/remote/state_test.go                 |  1 +
 5 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/backend/remote-state/consul/client_test.go b/backend/remote-state/consul/client_test.go
index bd52092ca5..52246e48ba 100644
--- a/backend/remote-state/consul/client_test.go
+++ b/backend/remote-state/consul/client_test.go
@@ -13,6 +13,7 @@ import (
 
 func TestRemoteClient_impl(t *testing.T) {
 	var _ remote.Client = new(RemoteClient)
+	var _ remote.ClientLocker = new(RemoteClient)
 }
 
 func TestRemoteClient(t *testing.T) {
diff --git a/state/backup_test.go b/state/backup_test.go
index f86b6b299f..85f722863c 100644
--- a/state/backup_test.go
+++ b/state/backup_test.go
@@ -6,6 +6,10 @@ import (
 	"testing"
 )
 
+func TestBackupState_locker(t *testing.T) {
+	var _ Locker = new(BackupState)
+}
+
 func TestBackupState(t *testing.T) {
 	f, err := ioutil.TempFile("", "tf")
 	if err != nil {
diff --git a/state/remote/remote.go b/state/remote/remote.go
index 020a352308..8bf99c2310 100644
--- a/state/remote/remote.go
+++ b/state/remote/remote.go
@@ -2,6 +2,8 @@ package remote
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/state"
 )
 
 // Client is the interface that must be implemented for a remote state
@@ -13,6 +15,15 @@ type Client interface {
 	Delete() error
 }
 
+// ClientLocker is an optional interface that allows a remote state
+// backend to enable state lock/unlock.
+type ClientLocker interface {
+	Client
+
+	Lock(*state.LockInfo) (string, error)
+	Unlock(string) error
+}
+
 // Payload is the return value from the remote state storage.
 type Payload struct {
 	MD5  []byte
diff --git a/state/remote/state.go b/state/remote/state.go
index 57d3b7c4ba..c874167052 100644
--- a/state/remote/state.go
+++ b/state/remote/state.go
@@ -3,6 +3,7 @@ package remote
 import (
 	"bytes"
 
+	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -62,24 +63,17 @@ func (s *State) PersistState() error {
 }
 
 // Lock calls the Client's Lock method if it's implemented.
-func (s *State) Lock(reason string) error {
-	if c, ok := s.Client.(stateLocker); ok {
-		return c.Lock(reason)
+func (s *State) Lock(info *state.LockInfo) (string, error) {
+	if c, ok := s.Client.(ClientLocker); ok {
+		return c.Lock(info)
 	}
-	return nil
+	return "", nil
 }
 
 // Unlock calls the Client's Unlock method if it's implemented.
-func (s *State) Unlock() error {
-	if c, ok := s.Client.(stateLocker); ok {
-		return c.Unlock()
+func (s *State) Unlock(id string) error {
+	if c, ok := s.Client.(ClientLocker); ok {
+		return c.Unlock(id)
 	}
 	return nil
 }
-
-// stateLocker mirrors the state.Locker interface.  This can be implemented by
-// Clients to provide methods for locking and unlocking remote state.
-type stateLocker interface {
-	Lock(reason string) error
-	Unlock() error
-}
diff --git a/state/remote/state_test.go b/state/remote/state_test.go
index 4878916675..01315b99ea 100644
--- a/state/remote/state_test.go
+++ b/state/remote/state_test.go
@@ -24,4 +24,5 @@ func TestState_impl(t *testing.T) {
 	var _ state.StateWriter = new(State)
 	var _ state.StatePersister = new(State)
 	var _ state.StateRefresher = new(State)
+	var _ state.Locker = new(State)
 }

From 9451acc5da0a18f3aead05067c0d4f8284aebaf8 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Wed, 15 Feb 2017 14:25:53 -0800
Subject: [PATCH 2/3] state/remote: add unit test to verify s3 is a
 ClientLocker as well

---
 state/remote/s3_test.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/state/remote/s3_test.go b/state/remote/s3_test.go
index 7a09835894..358c1a676c 100644
--- a/state/remote/s3_test.go
+++ b/state/remote/s3_test.go
@@ -13,6 +13,7 @@ import (
 
 func TestS3Client_impl(t *testing.T) {
 	var _ Client = new(S3Client)
+	var _ ClientLocker = new(S3Client)
 }
 
 func TestS3Factory(t *testing.T) {

From 03f6c650ca9e78fc0d80d430ca1ec2a52c262da4 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Wed, 15 Feb 2017 14:27:02 -0800
Subject: [PATCH 3/3] state/remote: ClientLocker is just a Client that is a
 state.Locker

---
 state/remote/remote.go | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/state/remote/remote.go b/state/remote/remote.go
index 8bf99c2310..414c115e9c 100644
--- a/state/remote/remote.go
+++ b/state/remote/remote.go
@@ -19,9 +19,7 @@ type Client interface {
 // backend to enable state lock/unlock.
 type ClientLocker interface {
 	Client
-
-	Lock(*state.LockInfo) (string, error)
-	Unlock(string) error
+	state.Locker
 }
 
 // Payload is the return value from the remote state storage.