helper/diff: calculate removed keys

helper/diff/resource_builder.go

@@ -55,20 +55,21 @@ func (b *ResourceBuilder) Diff(
 	flatRaw := flatmap.Flatten(c.Raw)
 	flatConfig := flatmap.Flatten(c.Config)
 
-	for k, v := range flatRaw {
-		// Make sure this is an attribute that actually affects
-		// the diff in some way.
-		var attr AttrType
 	for ak, at := range b.Attrs {
-			if strings.HasPrefix(k, ak) {
-				attr = at
-				break
-			}
-		}
-		if attr == AttrTypeUnknown {
+		// Keep track of all the keys we saw in the raw structure
+		// so that we can prune our attributes later.
+		seenKeys := make([]string, 0)
+
+		// Go through and find the added/changed keys in flatRaw
+		for k, v := range flatRaw {
+			// Find only the attributes that match our prefix
+			if !strings.HasPrefix(k, ak) {
 				continue
 			}
 
+			// Track that we saw this key
+			seenKeys = append(seenKeys, k)
+
 			// If this key is in the cleaned config, then use that value
 			// because it'll have its variables properly interpolated
 			if cleanV, ok := flatConfig[k]; ok {
@@ -91,12 +92,36 @@ func (b *ResourceBuilder) Diff(
 
 			// If this requires a new resource, record that and flag our
 			// boolean.
-		if attr == AttrTypeCreate {
+			if at == AttrTypeCreate {
 				attrs[k].RequiresNew = true
 				requiresNew = true
 			}
 		}
 
+		// Go through our attribues and find the deleted keys
+		matchingKeys := make(map[string]struct{})
+		for k, _ := range s.Attributes {
+			// Find only the attributes that match our prefix
+			if !strings.HasPrefix(k, ak) {
+				continue
+			}
+
+			matchingKeys[k] = struct{}{}
+		}
+
+		// Delete the keys we saw to find the deleted keys
+		for _, k := range seenKeys {
+			delete(matchingKeys, k)
+		}
+		for k, _ := range matchingKeys {
+			attrs[k] = &terraform.ResourceAttrDiff{
+				Old:  s.Attributes[k],
+				New:  "",
+				Type: terraform.DiffAttrInput,
+			}
+		}
+	}
+
 	// If we require a new resource, then process all the attributes
 	// that will be changing due to the creation of the resource.
 	if requiresNew {

helper/diff/resource_builder_test.go

@@ -46,6 +46,45 @@ func TestResourceBuilder_complex(t *testing.T) {
 	}
 }
 
+func TestResourceBuilder_complexReplace(t *testing.T) {
+	rb := &ResourceBuilder{
+		Attrs: map[string]AttrType{
+			"listener": AttrTypeUpdate,
+		},
+	}
+
+	state := &terraform.ResourceState{
+		ID: "foo",
+		Attributes: map[string]string{
+			"ignore":          "1",
+			"listener.#":      "1",
+			"listener.0.port": "80",
+		},
+	}
+
+	c := testConfig(t, map[string]interface{}{
+		"listener": []interface{}{
+			map[interface{}]interface{}{
+				"value": "50",
+			},
+		},
+	}, nil)
+
+	diff, err := rb.Diff(state, c)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if diff == nil {
+		t.Fatal("should not be nil")
+	}
+
+	actual := testResourceDiffStr(diff)
+	expected := testRBComplexReplaceDiff
+	if actual != expected {
+		t.Fatalf("bad: %s", actual)
+	}
+}
+
 func TestResourceBuilder_new(t *testing.T) {
 	rb := &ResourceBuilder{
 		Attrs: map[string]AttrType{
@@ -200,6 +239,11 @@ const testRBComplexDiff = `UPDATE
   IN  listener.0.port: "80" => "3000"
 `
 
+const testRBComplexReplaceDiff = `UPDATE
+  IN  listener.0.port:  "80" => ""
+  IN  listener.0.value: "" => "50"
+`
+
 const testRBNewDiff = `UPDATE
   IN  foo:        "" => "bar"
   OUT private_ip: "" => "<computed>"