Fix serializing same table multiple times.

Fixes #408

Author: khvzak

src/serde/de.rs

@@ -660,14 +660,14 @@ impl<'lua, 'de> de::VariantAccess<'de> for VariantDeserializer<'lua> {
 
 // Adds `ptr` to the `visited` map and removes on drop
 // Used to track recursive tables but allow to traverse same tables multiple times
-struct RecursionGuard {
+pub(crate) struct RecursionGuard {
     ptr: *const c_void,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
 impl RecursionGuard {
     #[inline]
-    fn new(table: &Table, visited: &Rc<RefCell<FxHashSet<*const c_void>>>) -> Self {
+    pub(crate) fn new(table: &Table, visited: &Rc<RefCell<FxHashSet<*const c_void>>>) -> Self {
         let visited = Rc::clone(visited);
         let ptr = table.to_pointer();
         visited.borrow_mut().insert(ptr);

src/table.rs

@@ -1089,7 +1089,7 @@ impl<'a, 'lua> Serialize for SerializableTable<'a, 'lua> {
     where
         S: Serializer,
     {
-        use crate::serde::de::{check_value_for_skip, MapPairs};
+        use crate::serde::de::{check_value_for_skip, MapPairs, RecursionGuard};
         use crate::value::SerializableValue;
 
         let convert_result = |res: Result<()>, serialize_err: Option<S::Error>| match res {
@@ -1101,15 +1101,15 @@ impl<'a, 'lua> Serialize for SerializableTable<'a, 'lua> {
 
         let options = self.options;
         let visited = &self.visited;
-        visited.borrow_mut().insert(self.table.to_pointer());
+        let _guard = RecursionGuard::new(&self.table, visited);
 
         // Array
         let len = self.table.raw_len();
         if len > 0 || self.table.is_array() {
             let mut seq = serializer.serialize_seq(Some(len))?;
             let mut serialize_err = None;
             let res = self.table.for_each_value::<Value>(|value| {
-                let skip = check_value_for_skip(&value, self.options, &self.visited)
+                let skip = check_value_for_skip(&value, self.options, visited)
                     .map_err(|err| Error::SerializeError(err.to_string()))?;
                 if skip {
                     // continue iteration
@@ -1129,9 +1129,9 @@ impl<'a, 'lua> Serialize for SerializableTable<'a, 'lua> {
         let mut map = serializer.serialize_map(None)?;
         let mut serialize_err = None;
         let mut process_pair = |key, value| {
-            let skip_key = check_value_for_skip(&key, self.options, &self.visited)
+            let skip_key = check_value_for_skip(&key, self.options, visited)
                 .map_err(|err| Error::SerializeError(err.to_string()))?;
-            let skip_value = check_value_for_skip(&value, self.options, &self.visited)
+            let skip_value = check_value_for_skip(&value, self.options, visited)
                 .map_err(|err| Error::SerializeError(err.to_string()))?;
             if skip_key || skip_value {
                 // continue iteration

tests/serde.rs

@@ -269,6 +269,27 @@ fn test_serialize_globals() -> LuaResult<()> {
     Ok(())
 }
 
+#[test]
+fn test_serialize_same_table_twice() -> LuaResult<()> {
+    let lua = Lua::new();
+
+    let value = lua
+        .load(
+            r#"
+        local foo = {}
+        return {
+            a = foo,
+            b = foo,
+        }
+    "#,
+        )
+        .eval::<Value>()?;
+    let json = serde_json::to_string(&value.to_serializable().sort_keys(true)).unwrap();
+    assert_eq!(json, r#"{"a":{},"b":{}}"#);
+
+    Ok(())
+}
+
 #[test]
 fn test_to_value_struct() -> LuaResult<()> {
     let lua = Lua::new();