encoder: inline tables create map in nil interface (#496)

Co-authored-by: Thomas Pelletier <pelletier.thomas@gmail.com>

targets.go

@@ -159,6 +159,14 @@ func ensureValueIndexable(t target) error {
 var sliceInterfaceType = reflect.TypeOf([]interface{}{})
 var mapStringInterfaceType = reflect.TypeOf(map[string]interface{}{})
 
+func ensureMapIfInterface(x target) {
+	v := x.get()
+	if v.Kind() == reflect.Interface && v.IsNil() {
+		newElement := reflect.MakeMap(mapStringInterfaceType)
+		x.set(newElement)
+	}
+}
+
 func setString(t target, v string) error {
 	f := t.get()
 

unmarshaler.go

@@ -120,11 +120,7 @@ func (d *decoder) fromParser(p *parser, v interface{}) error {
 				// looks like a table. Otherwise the information
 				// of a table is lost, and marshal cannot do the
 				// round trip.
-				v := current.get()
-				if v.Kind() == reflect.Interface && v.IsNil() {
-					newElement := reflect.MakeMap(mapStringInterfaceType)
-					current.set(newElement)
-				}
+				ensureMapIfInterface(current)
 			}
 		case ast.ArrayTable:
 			current, found, err = d.scopeWithArrayTable(root, node.Key())
@@ -381,6 +377,8 @@ func unmarshalFloat(x target, node ast.Node) error {
 func (d *decoder) unmarshalInlineTable(x target, node ast.Node) error {
 	assertNode(ast.InlineTable, node)
 
+	ensureMapIfInterface(x)
+
 	it := node.Children()
 	for it.Next() {
 		n := it.Node()

unmarshaler_test.go

@@ -296,6 +296,17 @@ B = "data"`,
 				}
 			},
 		},
+		{
+			desc:  "standard empty table",
+			input: `[A]`,
+			gen: func() test {
+				var v map[string]interface{}
+				return test{
+					target:   &v,
+					expected: &map[string]interface{}{`A`: map[string]interface{}{}},
+				}
+			},
+		},
 		{
 			desc:  "inline table",
 			input: `Name = {First = "hello", Last = "world"}`,
@@ -316,6 +327,17 @@ B = "data"`,
 				}
 			},
 		},
+		{
+			desc:  "inline empty table",
+			input: `A = {}`,
+			gen: func() test {
+				var v map[string]interface{}
+				return test{
+					target:   &v,
+					expected: &map[string]interface{}{`A`: map[string]interface{}{}},
+				}
+			},
+		},
 		{
 			desc:  "inline table inside array",
 			input: `Names = [{First = "hello", Last = "world"}, {First = "ab", Last = "cd"}]`,
@@ -713,6 +735,7 @@ type Integer484 struct {
 func (i Integer484) MarshalText() ([]byte, error) {
 	return []byte(strconv.Itoa(i.Value)), nil
 }
+
 func (i *Integer484) UnmarshalText(data []byte) error {
 	conv, err := strconv.Atoi(string(data))
 	if err != nil {
@@ -895,7 +918,7 @@ func TestIssue287(t *testing.T) {
 	expected := map[string]interface{}{
 		"y": []interface{}{
 			[]interface{}{
-				nil,
+				map[string]interface{}{},
 			},
 		},
 	}