decode: allow subtables to be defined later (#750)

Fixes #739

internal/tracker/seen.go

@@ -79,6 +79,7 @@ type entry struct {
 	name     []byte
 	kind     keyKind
 	explicit bool
+	kv       bool
 }
 
 // Find the index of the child of parentIdx with key k. Returns -1 if
@@ -111,7 +112,7 @@ func (s *SeenTracker) clear(idx int) {
 	s.entries[idx].child = -1
 }
 
-func (s *SeenTracker) create(parentIdx int, name []byte, kind keyKind, explicit bool) int {
+func (s *SeenTracker) create(parentIdx int, name []byte, kind keyKind, explicit bool, kv bool) int {
 	e := entry{
 		child: -1,
 		next:  s.entries[parentIdx].child,
@@ -119,6 +120,7 @@ func (s *SeenTracker) create(parentIdx int, name []byte, kind keyKind, explicit
 		name:     name,
 		kind:     kind,
 		explicit: explicit,
+		kv:       kv,
 	}
 	var idx int
 	if s.entries[0].next >= 0 {
@@ -137,7 +139,10 @@ func (s *SeenTracker) create(parentIdx int, name []byte, kind keyKind, explicit
 
 func (s *SeenTracker) setExplicitFlag(parentIdx int) {
 	for i := s.entries[parentIdx].child; i >= 0; i = s.entries[i].next {
+		if s.entries[i].kv {
 			s.entries[i].explicit = true
+			s.entries[i].kv = false
+		}
 		s.setExplicitFlag(i)
 	}
 }
@@ -183,7 +188,7 @@ func (s *SeenTracker) checkTable(node *ast.Node) error {
 		idx := s.find(parentIdx, k)
 
 		if idx < 0 {
-			idx = s.create(parentIdx, k, tableKind, false)
+			idx = s.create(parentIdx, k, tableKind, false, false)
 		} else {
 			entry := s.entries[idx]
 			if entry.kind == valueKind {
@@ -206,7 +211,7 @@ func (s *SeenTracker) checkTable(node *ast.Node) error {
 		}
 		s.entries[idx].explicit = true
 	} else {
-		idx = s.create(parentIdx, k, tableKind, true)
+		idx = s.create(parentIdx, k, tableKind, true, false)
 	}
 
 	s.currentIdx = idx
@@ -233,7 +238,7 @@ func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
 		idx := s.find(parentIdx, k)
 
 		if idx < 0 {
-			idx = s.create(parentIdx, k, tableKind, false)
+			idx = s.create(parentIdx, k, tableKind, false, false)
 		} else {
 			entry := s.entries[idx]
 			if entry.kind == valueKind {
@@ -254,7 +259,7 @@ func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
 		}
 		s.clear(idx)
 	} else {
-		idx = s.create(parentIdx, k, arrayTableKind, true)
+		idx = s.create(parentIdx, k, arrayTableKind, true, false)
 	}
 
 	s.currentIdx = idx
@@ -272,7 +277,7 @@ func (s *SeenTracker) checkKeyValue(node *ast.Node) error {
 		idx := s.find(parentIdx, k)
 
 		if idx < 0 {
-			idx = s.create(parentIdx, k, tableKind, false)
+			idx = s.create(parentIdx, k, tableKind, false, true)
 		} else {
 			entry := s.entries[idx]
 			if it.IsLast() {

internal/tracker/seen_test.go

@@ -0,0 +1,15 @@
+package tracker
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestEntrySize(t *testing.T) {
+	// Validate no regression on the size of entry{}. This is a critical bit for
+	// performance of unmarshaling documents. Should only be increased with care
+	// and a very good reason.
+	require.LessOrEqual(t, 48, int(unsafe.Sizeof(entry{})))
+}

unmarshaler_test.go

@@ -545,6 +545,35 @@ func TestUnmarshal(t *testing.T) {
 				}
 			},
 		},
+		{
+			desc: "issue 739 - table redefinition",
+			input: `
+[foo.bar.baz]
+wibble = 'wobble'
+
+[foo]
+
+[foo.bar]
+huey = 'dewey'			
+			`,
+			gen: func() test {
+				m := map[string]interface{}{}
+
+				return test{
+					target: &m,
+					expected: &map[string]interface{}{
+						`foo`: map[string]interface{}{
+							"bar": map[string]interface{}{
+								"huey": "dewey",
+								"baz": map[string]interface{}{
+									"wibble": "wobble",
+								},
+							},
+						},
+					},
+				}
+			},
+		},
 		{
 			desc: "multiline basic string",
 			input: `A = """\