track the visited structures in the checkStruct fucntion

fix #16 with stack overflow issue when a struct has the fields of self type

musttag.go

@@ -131,6 +131,7 @@ func run(pass *analysis.Pass, funcs map[string]Func) (any, error) {
 
 	walk := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	filter := []ast.Node{(*ast.CallExpr)(nil)}
+	visited := make(map[string]struct{})
 
 	walk.Preorder(filter, func(n ast.Node) {
 		call, ok := n.(*ast.CallExpr)
@@ -171,7 +172,7 @@ func run(pass *analysis.Pass, funcs map[string]Func) (any, error) {
 			return // not a struct argument.
 		}
 
-		reportPos, ok := checkStruct(s, fn.Tag)
+		reportPos, ok := checkStruct(s, fn.Tag, visited)
 		if ok {
 			return // nothing to report.
 		}
@@ -222,7 +223,8 @@ func parseStruct(t types.Type, pos token.Pos) (*structInfo, bool) {
 
 // checkStruct recursively checks the given struct and returns the position for report,
 // in case one of its fields is missing the tag.
-func checkStruct(s *structInfo, tag string) (token.Pos, bool) {
+func checkStruct(s *structInfo, tag string, visited map[string]struct{}) (token.Pos, bool) {
+	visited[s.String()] = struct{}{}
 	for i := 0; i < s.NumFields(); i++ {
 		if !s.Field(i).Exported() {
 			continue
@@ -238,7 +240,10 @@ func checkStruct(s *structInfo, tag string) (token.Pos, bool) {
 		if !ok {
 			continue
 		}
-		if pos, ok := checkStruct(nested, tag); !ok {
+		if _, ok := visited[nested.String()]; ok {
+			continue
+		}
+		if pos, ok := checkStruct(nested, tag, visited); !ok {
 			return pos, false
 		}
 	}

testdata/src/tests/tests.go

@@ -468,3 +468,14 @@ func nonStructArgument() {
 	custom.Marshal(0)
 	custom.Unmarshal(nil, &[]int{})
 }
+
+// test for stack overflow issue: https://github.com/junk1tm/musttag/issues/16
+func selfType() {
+	type Human struct {
+		Mom      *Human   `json:"mom"`
+		Dad      *Human   `json:"dad"`
+		Children []*Human `json:"children"`
+	}
+	var v *Human
+	json.Marshal(v)
+}