From 0d4c7887c5c918abd1b6212fb0593676fbb89699 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Wed, 25 Mar 2015 15:38:24 -0700
Subject: [PATCH 1/3] terraform: don't increment state if one is nil

---
 terraform/state.go      |  9 +++++++++
 terraform/state_test.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/terraform/state.go b/terraform/state.go
index 42e9023baa..4ec772fd20 100644
--- a/terraform/state.go
+++ b/terraform/state.go
@@ -214,6 +214,15 @@ func (s *State) DeepCopy() *State {
 // IncrementSerialMaybe increments the serial number of this state
 // if it different from the other state.
 func (s *State) IncrementSerialMaybe(other *State) {
+	if s == nil {
+		return
+	}
+	if other == nil {
+		return
+	}
+	if s.Serial > other.Serial {
+		return
+	}
 	if !s.Equal(other) {
 		s.Serial++
 	}
diff --git a/terraform/state_test.go b/terraform/state_test.go
index 9dfbbbf04e..91f9170c71 100644
--- a/terraform/state_test.go
+++ b/terraform/state_test.go
@@ -178,6 +178,40 @@ func TestStateEqual(t *testing.T) {
 	}
 }
 
+func TestStateIncrementSerialMaybe(t *testing.T) {
+	cases := map[string]struct {
+		S1, S2 *State
+		Serial int64
+	}{
+		"S2 is nil": {
+			&State{},
+			nil,
+			0,
+		},
+		"S2 is identical": {
+			&State{},
+			&State{},
+			0,
+		},
+		"S2 is different": {
+			&State{},
+			&State{
+				Modules: []*ModuleState{
+					&ModuleState{Path: rootModulePath},
+				},
+			},
+			1,
+		},
+	}
+
+	for name, tc := range cases {
+		tc.S1.IncrementSerialMaybe(tc.S2)
+		if tc.S1.Serial != tc.Serial {
+			t.Fatalf("Bad: %s\nGot: %d", name, tc.S1.Serial)
+		}
+	}
+}
+
 func TestResourceStateEqual(t *testing.T) {
 	cases := []struct {
 		Result   bool

From f68f285f721d062e18bddade510277c6d9997c55 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Wed, 25 Mar 2015 15:39:33 -0700
Subject: [PATCH 2/3] terraform: test case for higher S1 serial

---
 terraform/state_test.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/terraform/state_test.go b/terraform/state_test.go
index 91f9170c71..e222b1b722 100644
--- a/terraform/state_test.go
+++ b/terraform/state_test.go
@@ -202,6 +202,16 @@ func TestStateIncrementSerialMaybe(t *testing.T) {
 			},
 			1,
 		},
+		"S1 serial is higher": {
+			&State{Serial: 5},
+			&State{
+				Serial: 3,
+				Modules: []*ModuleState{
+					&ModuleState{Path: rootModulePath},
+				},
+			},
+			5,
+		},
 	}
 
 	for name, tc := range cases {

From 9c6e2cdc2167abba570a1a87ab492ef73a41e628 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Wed, 25 Mar 2015 15:40:53 -0700
Subject: [PATCH 3/3] terraform: make sure our serial is always higher

---
 terraform/state.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/terraform/state.go b/terraform/state.go
index 4ec772fd20..1a1a28bea8 100644
--- a/terraform/state.go
+++ b/terraform/state.go
@@ -224,6 +224,10 @@ func (s *State) IncrementSerialMaybe(other *State) {
 		return
 	}
 	if !s.Equal(other) {
+		if other.Serial > s.Serial {
+			s.Serial = other.Serial
+		}
+
 		s.Serial++
 	}
 }