From 068e8c647e7c419daa23a6568122f1ac1d48f593 Mon Sep 17 00:00:00 2001
From: Stephen Chung <schungx@live.com>
Date: Thu, 2 Dec 2021 12:50:11 +0800
Subject: [PATCH] Support Option in from_dynamic.

---
 CHANGELOG.md    |  5 +++++
 src/serde/de.rs | 11 +++++++++--
 tests/serde.rs  | 29 +++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 87c29f08..cb4a4bda 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,11 @@ Rhai Release Notes
 Version 1.2.2
 =============
 
+Bug fixes
+---------
+
+* `from_dynamic` now supports deserializing `Option`.
+
 
 Version 1.2.1
 =============
diff --git a/src/serde/de.rs b/src/serde/de.rs
index 8c7420e2..d860c3e4 100644
--- a/src/serde/de.rs
+++ b/src/serde/de.rs
@@ -363,8 +363,15 @@ impl<'de> Deserializer<'de> for &mut DynamicDeserializer<'de> {
         self.type_error()
     }
 
-    fn deserialize_option<V: Visitor<'de>>(self, _: V) -> Result<V::Value, Box<EvalAltResult>> {
-        self.type_error()
+    fn deserialize_option<V: Visitor<'de>>(
+        self,
+        visitor: V,
+    ) -> Result<V::Value, Box<EvalAltResult>> {
+        if self.value.is::<()>() {
+            visitor.visit_none()
+        } else {
+            visitor.visit_some(self)
+        }
     }
 
     fn deserialize_unit<V: Visitor<'de>>(self, visitor: V) -> Result<V::Value, Box<EvalAltResult>> {
diff --git a/tests/serde.rs b/tests/serde.rs
index ac98dc37..95bde973 100644
--- a/tests/serde.rs
+++ b/tests/serde.rs
@@ -746,3 +746,32 @@ fn test_serde_json() -> serde_json::Result<()> {
 
     Ok(())
 }
+
+#[test]
+#[cfg(not(feature = "no_object"))]
+fn test_serde_optional() -> Result<(), Box<EvalAltResult>> {
+    #[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
+    struct TestStruct {
+        foo: Option<char>,
+    }
+
+    let mut engine = Engine::new();
+    engine.register_type_with_name::<TestStruct>("TestStruct");
+
+    let r = engine.eval::<Dynamic>("#{ foo: 'a' }")?;
+
+    assert_eq!(
+        from_dynamic::<TestStruct>(&r)?,
+        TestStruct { foo: Some('a') }
+    );
+
+    let r = engine.eval::<Dynamic>("#{ foo: () }")?;
+
+    assert_eq!(from_dynamic::<TestStruct>(&r)?, TestStruct { foo: None });
+
+    let r = engine.eval::<Dynamic>("#{ }")?;
+
+    assert_eq!(from_dynamic::<TestStruct>(&r)?, TestStruct { foo: None });
+
+    Ok(())
+}