terraform: test case for decreasing the count

terraform/context.go

@@ -630,7 +630,9 @@ func computeAggregateVars(
 	var ivars map[string]config.InterpolatedVariable
 	switch m := n.Meta.(type) {
 	case *GraphNodeResource:
-		ivars = m.Config.RawConfig.Variables
+		if m.Config != nil {
+			ivars = m.Config.RawConfig.Variables
+		}
 	case *GraphNodeResourceProvider:
 		if m.Config != nil {
 			ivars = m.Config.RawConfig.Variables

terraform/context_test.go

@@ -668,6 +668,50 @@ func TestContextPlan_count(t *testing.T) {
 	}
 }
 
+func TestContextPlan_countDecrease(t *testing.T) {
+	c := testConfig(t, "plan-count-dec")
+	p := testProvider("aws")
+	p.DiffFn = testDiffFn
+	s := &State{
+		Resources: map[string]*ResourceState{
+			"aws_instance.foo.0": &ResourceState{
+				ID:   "bar",
+				Type: "aws_instance",
+				Attributes: map[string]string{
+					"foo":  "foo",
+					"type": "aws_instance",
+				},
+			},
+			"aws_instance.foo.1": &ResourceState{
+				ID:   "bar",
+				Type: "aws_instance",
+			},
+			"aws_instance.foo.2": &ResourceState{
+				ID:   "bar",
+				Type: "aws_instance",
+			},
+		},
+	}
+	ctx := testContext(t, &ContextOpts{
+		Config: c,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		State: s,
+	})
+
+	plan, err := ctx.Plan(nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actual := strings.TrimSpace(plan.String())
+	expected := strings.TrimSpace(testTerraformPlanCountDecreaseStr)
+	if actual != expected {
+		t.Fatalf("bad:\n%s", actual)
+	}
+}
+
 func TestContextPlan_destroy(t *testing.T) {
 	c := testConfig(t, "plan-destroy")
 	p := testProvider("aws")
@@ -944,10 +988,6 @@ func testDiffFn(
 	c *ResourceConfig) (*ResourceDiff, error) {
 	var diff ResourceDiff
 	diff.Attributes = make(map[string]*ResourceAttrDiff)
-	diff.Attributes["type"] = &ResourceAttrDiff{
-		Old: "",
-		New: s.Type,
-	}
 
 	for k, v := range c.Raw {
 		if _, ok := v.(string); !ok {
@@ -1009,6 +1049,27 @@ func testDiffFn(
 		}
 	}
 
+	for k, v := range diff.Attributes {
+		if v.NewComputed {
+			continue
+		}
+
+		old, ok := s.Attributes[k]
+		if !ok {
+			continue
+		}
+		if old == v.New {
+			delete(diff.Attributes, k)
+		}
+	}
+
+	if !diff.Empty() {
+		diff.Attributes["type"] = &ResourceAttrDiff{
+			Old: "",
+			New: s.Type,
+		}
+	}
+
 	return &diff, nil
 }
 

terraform/graph.go

@@ -156,16 +156,6 @@ func graphAddConfigResources(
 	// This tracks all the resource nouns
 	nouns := make(map[string]*depgraph.Noun)
 	for _, r := range c.Resources {
-		var state *ResourceState
-		if s != nil {
-			state = s.Resources[r.Id()]
-		}
-		if state == nil {
-			state = &ResourceState{
-				Type: r.Type,
-			}
-		}
-
 		resourceNouns := make([]*depgraph.Noun, r.Count)
 		for i := 0; i < r.Count; i++ {
 			name := r.Id()
@@ -178,6 +168,22 @@ func graphAddConfigResources(
 				index = i
 			}
 
+			var state *ResourceState
+			if s != nil {
+				state = s.Resources[name]
+
+				// If the count is one, check the state for ".0" appended, which
+				// might exist if we go from count > 1 to count == 1.
+				if state == nil && r.Count == 1 {
+					state = s.Resources[r.Id()+".0"]
+				}
+			}
+			if state == nil {
+				state = &ResourceState{
+					Type: r.Type,
+				}
+			}
+
 			resourceNouns[i] = &depgraph.Noun{
 				Name: name,
 				Meta: &GraphNodeResource{

terraform/state.go

@@ -38,6 +38,12 @@ func (s *State) Orphans(c *config.Config) []string {
 
 	for _, r := range c.Resources {
 		delete(keys, r.Id())
+
+		// If there is only one of this instance, then we alias that
+		// to the ".0" version as well so that it can count
+		if r.Count == 1 {
+			delete(keys, r.Id()+".0")
+		}
 	}
 
 	result := make([]string, 0, len(keys))

terraform/terraform_test.go

@@ -182,6 +182,27 @@ STATE:
 <no state>
 `
 
+const testTerraformPlanCountDecreaseStr = `
+DIFF:
+
+UPDATE: aws_instance.bar
+  foo:  "" => "bar"
+  type: "" => "aws_instance"
+DESTROY: aws_instance.foo.1
+DESTROY: aws_instance.foo.2
+
+STATE:
+
+aws_instance.foo.0:
+  ID = bar
+  foo = foo
+  type = aws_instance
+aws_instance.foo.1:
+  ID = bar
+aws_instance.foo.2:
+  ID = bar
+`
+
 const testTerraformPlanDestroyStr = `
 DIFF:
 

terraform/test-fixtures/plan-count-dec/main.tf

@@ -0,0 +1,7 @@
+resource "aws_instance" "foo" {
+    foo = "foo"
+}
+
+resource "aws_instance" "bar" {
+    foo = "bar"
+}