Fix unused keys

decoder.go

@@ -404,6 +404,11 @@ func (d *decoder) decodeMap(name string, node ast.Node, result reflect.Value) er
 }
 
 func (d *decoder) decodePtr(name string, node ast.Node, result reflect.Value) error {
+	// if pointer is not nil, decode into existing value
+	if !result.IsNil() {
+		return d.decode(name, node, result.Elem())
+	}
+
 	// Create an element of the concrete (non pointer) type and decode
 	// into that. Then set the value of the pointer to this type.
 	resultType := result.Type()
@@ -512,7 +517,7 @@ func expandObject(node ast.Node, result reflect.Value) ast.Node {
 	// we need to un-flatten the ast enough to decode
 	newNode := &ast.ObjectItem{
 		Keys: []*ast.ObjectKey{
-			&ast.ObjectKey{
+			{
 				Token: keyToken,
 			},
 		},
@@ -631,10 +636,19 @@ func (d *decoder) decodeStruct(name string, node ast.Node, result reflect.Value)
 		}
 	}
 
-	usedKeys := make(map[string]struct{})
 	decodedFields := make([]string, 0, len(fields))
 	decodedFieldsVal := make([]reflect.Value, 0)
 	unusedKeysVal := make([]reflect.Value, 0)
+
+	// fill unusedNodeKeys with keys from the AST
+	// a slice because we have to do equals case fold to match Filter
+	unusedNodeKeys := make([]string, 0)
+	for _, item := range list.Items {
+		for _, k := range item.Keys {
+			unusedNodeKeys = append(unusedNodeKeys, k.Token.Value().(string))
+		}
+	}
+
 	for _, f := range fields {
 		field, fieldValue := f.field, f.val
 		if !fieldValue.IsValid() {
@@ -689,8 +703,8 @@ func (d *decoder) decodeStruct(name string, node ast.Node, result reflect.Value)
 			continue
 		}
 
-		// Track the used key
-		usedKeys[fieldName] = struct{}{}
+		// Track the used keys
+		unusedNodeKeys = removeCaseFold(unusedNodeKeys, fieldName)
 
 		// Create the field name and decode. We range over the elements
 		// because we actually want the value.
@@ -723,6 +737,14 @@ func (d *decoder) decodeStruct(name string, node ast.Node, result reflect.Value)
 		}
 	}
 
+	if len(unusedNodeKeys) > 0 {
+		// like decodedFields, populated the unusedKeys field(s)
+		sort.Strings(unusedNodeKeys)
+		for _, v := range unusedKeysVal {
+			v.Set(reflect.ValueOf(unusedNodeKeys))
+		}
+	}
+
 	return nil
 }
 
@@ -734,3 +756,12 @@ func findNodeType() reflect.Type {
 	value := reflect.ValueOf(nodeContainer).FieldByName("Node")
 	return value.Type()
 }
+
+func removeCaseFold(xs []string, y string) []string {
+	for i, x := range xs {
+		if strings.EqualFold(x, y) {
+			return append(xs[:i], xs[i+1:]...)
+		}
+	}
+	return xs
+}

decoder_test.go

@@ -616,6 +616,35 @@ func TestDecode_structurePtr(t *testing.T) {
 	}
 }
 
+func TestDecode_nonNilStructurePtr(t *testing.T) {
+	type V struct {
+		Key        int
+		Foo        string
+		DontChange string
+	}
+
+	actual := &V{
+		Key:        42,
+		Foo:        "foo",
+		DontChange: "don't change me",
+	}
+
+	err := Decode(&actual, testReadFile(t, "flat.hcl"))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	expected := &V{
+		Key:        7,
+		Foo:        "bar",
+		DontChange: "don't change me",
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("Actual: %#v\n\nExpected: %#v", actual, expected)
+	}
+}
+
 func TestDecode_structureArray(t *testing.T) {
 	// This test is extracted from a failure in Consul (consul.io),
 	// hence the interesting structure naming.
@@ -786,6 +815,36 @@ func TestDecode_structureMapInvalid(t *testing.T) {
 	}
 }
 
+func TestDecode_structureMapExtraKeys(t *testing.T) {
+	type hclVariable struct {
+		A     int
+		B     int
+		Found []string `hcl:",decodedFields"`
+		Extra []string `hcl:",unusedKeys"`
+	}
+
+	q := hclVariable{
+		A:     1,
+		B:     2,
+		Found: []string{"A", "B"},
+		Extra: []string{"extra1", "extra2"},
+	}
+
+	var p hclVariable
+	ast, _ := Parse(testReadFile(t, "structure_map_extra_keys.hcl"))
+	DecodeObject(&p, ast)
+	if !reflect.DeepEqual(p, q) {
+		t.Fatal("not equal")
+	}
+
+	var j hclVariable
+	ast, _ = Parse(testReadFile(t, "structure_map_extra_keys.json"))
+	DecodeObject(&j, ast)
+	if !reflect.DeepEqual(p, j) {
+		t.Fatal("not equal")
+	}
+}
+
 func TestDecode_interfaceNonPointer(t *testing.T) {
 	var value interface{}
 	err := Decode(value, testReadFile(t, "basic_int_string.hcl"))

hcl/parser/parser_test.go

@@ -240,7 +240,7 @@ func TestListType_lineComment(t *testing.T) {
 			comment := l.comment[i]
 
 			if (lt.LineComment == nil) != (comment == "") {
-				t.Fatalf("bad: %s", lt)
+				t.Fatalf("bad: %s", lt.Token.Value())
 			}
 
 			if comment == "" {

test-fixtures/structure_map_extra_keys.hcl

@@ -0,0 +1,4 @@
+a = 1
+b = 2
+extra1 = 3
+extra2 = 4

test-fixtures/structure_map_extra_keys.json

@@ -0,0 +1,6 @@
+{
+	"a": 1,
+	"b": 2,
+	"extra1": 3,
+	"extra2": 4
+}