From 6c2a694486d1206cc495744d61b377fc321bafed Mon Sep 17 00:00:00 2001
From: Sergey Vilgelm <sergey@vilgelm.com>
Date: Thu, 9 Feb 2023 22:28:38 -0800
Subject: [PATCH] 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                  | 10 +++++++---
 testdata/src/tests/tests.go | 11 +++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/musttag.go b/musttag.go
index 121777b..4371cd1 100644
--- a/musttag.go
+++ b/musttag.go
@@ -171,7 +171,7 @@ 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, make(map[string]struct{}))
 		if ok {
 			return // nothing to report.
 		}
@@ -222,7 +222,8 @@ 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 +239,10 @@ 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
 		}
 	}
diff --git a/testdata/src/tests/tests.go b/testdata/src/tests/tests.go
index 007328c..7a2013f 100644
--- a/testdata/src/tests/tests.go
+++ b/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)
+}