helper/schema: setting empty map works [GH-464]

helper/schema/resource_data.go

@@ -465,6 +465,11 @@ func (d *ResourceData) getMap(
 	if !exact || level == getSourceSet {
 		if d.setMap != nil && level >= getSourceSet {
 			cleared := false
+			if v, ok := d.setMap[k]; ok && v == "" {
+				// We've cleared the map
+				result = make(map[string]interface{})
+				resultSet = true
+			} else {
 				for k, _ := range d.setMap {
 					if !strings.HasPrefix(k, prefix) {
 						continue
@@ -478,7 +483,9 @@ func (d *ResourceData) getMap(
 					}
 
 					single := k[len(prefix):]
-				result[single] = d.getPrimitive(k, nil, elemSchema, source).Value
+					result[single] = d.getPrimitive(
+						k, nil, elemSchema, source).Value
+				}
 			}
 		}
 	}
@@ -783,14 +790,6 @@ func (d *ResourceData) setMapValue(
 		return fmt.Errorf("%s: full map must be set, no a single element", k)
 	}
 
-	// Delete any prior map set
-	/*
-		v := d.getMap(k, nil, schema, getSourceSet)
-		for subKey, _ := range v.(map[string]interface{}) {
-			delete(d.setMap, fmt.Sprintf("%s.%s", k, subKey))
-		}
-	*/
-
 	v := reflect.ValueOf(value)
 	if v.Kind() != reflect.Map {
 		return fmt.Errorf("%s: must be a map", k)
@@ -804,6 +803,13 @@ func (d *ResourceData) setMapValue(
 		vs[mk.String()] = mv.Interface()
 	}
 
+	if len(vs) == 0 {
+		// The empty string here means the map is removed.
+		d.setMap[k] = ""
+		return nil
+	}
+
+	delete(d.setMap, k)
 	for subKey, v := range vs {
 		err := d.set(fmt.Sprintf("%s.%s", k, subKey), nil, elemSchema, v)
 		if err != nil {

helper/schema/resource_data_test.go

@@ -2193,6 +2193,63 @@ func TestResourceDataState(t *testing.T) {
 				},
 			},
 		},
+
+		// Maps
+		{
+			Schema: map[string]*Schema{
+				"tags": &Schema{
+					Type:     TypeMap,
+					Optional: true,
+					Computed: true,
+				},
+			},
+
+			State: nil,
+
+			Diff: &terraform.InstanceDiff{
+				Attributes: map[string]*terraform.ResourceAttrDiff{
+					"tags.Name": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "foo",
+					},
+				},
+			},
+
+			Result: &terraform.InstanceState{
+				Attributes: map[string]string{
+					"tags.Name": "foo",
+				},
+			},
+		},
+
+		{
+			Schema: map[string]*Schema{
+				"tags": &Schema{
+					Type:     TypeMap,
+					Optional: true,
+					Computed: true,
+				},
+			},
+
+			State: nil,
+
+			Diff: &terraform.InstanceDiff{
+				Attributes: map[string]*terraform.ResourceAttrDiff{
+					"tags.Name": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "foo",
+					},
+				},
+			},
+
+			Set: map[string]interface{}{
+				"tags": map[string]string{},
+			},
+
+			Result: &terraform.InstanceState{
+				Attributes: map[string]string{},
+			},
+		},
 	}
 
 	for i, tc := range cases {