fix(reflect): deep nested struct cause panic

internal/reflect/desc.go

@@ -92,23 +92,36 @@ func newStructDescAndPrefetch(t reflect.Type) (*structDesc, error) {
 
 func prefetchSubStructDesc(d *structDesc) error {
 	for i := range d.fields {
-		var t *tType
 		f := d.fields[i]
-		if f.Type.T == tSTRUCT {
-			t = f.Type
-		} else if f.Type.T == tMAP && f.Type.V.T == tSTRUCT {
-			t = f.Type.V
-		} else if f.Type.T == tLIST && f.Type.V.T == tSTRUCT {
-			t = f.Type.V
-		} else {
-			continue
+		switch f.Type.T {
+		case tSTRUCT, tMAP, tLIST, tSET:
+			if err := fetchStructDesc(f.Type); err != nil {
+				return err
+			}
 		}
-		sd, err := newStructDescAndPrefetch(t.RT)
+	}
+	return nil
+}
+
+func fetchStructDesc(t *tType) error {
+	if t.T == tMAP {
+		err := fetchStructDesc(t.K)
 		if err != nil {
 			return err
 		}
-		t.Sd = sd
+		return fetchStructDesc(t.V)
+	}
+	if t.T == tLIST || t.T == tSET {
+		return fetchStructDesc(t.V)
+	}
+	if t.T != tSTRUCT || t.Sd != nil {
+		return nil
+	}
+	sd, err := newStructDescAndPrefetch(t.RT)
+	if err != nil {
+		return err
 	}
+	t.Sd = sd
 	return nil
 }
 

internal/reflect/encoder_test.go

@@ -145,3 +145,28 @@ func TestEncodeUnknownFields(t *testing.T) {
 	assert.Equal(t, n, len(b))
 	assert.Contains(t, string(b), string(append([]byte("helloworld")[:], byte(tSTOP))))
 }
+
+func TestNestedListMapStruct(t *testing.T) {
+	type Msg1 struct {
+		A string `frugal:"1,default,string"`
+		B string `frugal:"2,default,string"`
+	}
+	type Msg2 struct {
+		Msgs []map[string]*Msg1 `thrift:"item_list,2" frugal:"2,default,list<map<string:Msg1>>" json:"item_list"`
+	}
+	p := &Msg2{}
+	p.Msgs = make([]map[string]*Msg1, 0, 1)
+	p.Msgs = append(p.Msgs, map[string]*Msg1{})
+	p.Msgs[0]["32"] = &Msg1{A: "Hello", B: "World"}
+
+	b := make([]byte, EncodedSize(p))
+	x, err := Append(b[:0], p)
+	require.NoError(t, err)
+	require.Equal(t, len(x), len(b))
+
+	p2 := &Msg2{}
+	i, err := Decode(x, p2)
+	require.NoError(t, err)
+	require.Equal(t, i, len(b))
+	require.Equal(t, p, p2)
+}