fix(neon): Allow extracting Json<Option<T>> when value is undefined

crates/neon/src/types_impl/extract/json.rs

@@ -23,7 +23,7 @@ use crate::{
     result::{JsResult, NeonResult},
     types::{
         extract::{private, TryFromJs, TryIntoJs},
-        JsError, JsFunction, JsObject, JsString, JsValue,
+        JsError, JsFunction, JsObject, JsValue,
     },
 };
 
@@ -52,13 +52,6 @@ fn json_stringify<'cx>(cx: &mut Cx<'cx>) -> JsResult<'cx, JsFunction> {
         .map(|f| f.to_inner(cx))
 }
 
-fn stringify(cx: &mut Cx, v: Handle<JsValue>) -> NeonResult<String> {
-    json_stringify(cx)?
-        .call(cx, v, [v])?
-        .downcast_or_throw::<JsString, _>(cx)
-        .map(|s| s.value(cx))
-}
-
 fn global_json_parse<'cx>(cx: &mut Cx<'cx>) -> JsResult<'cx, JsFunction> {
     cx.global::<JsObject>("JSON")?.get(cx, "parse")
 }
@@ -97,9 +90,14 @@ where
         cx: &mut Cx<'cx>,
         v: Handle<'cx, JsValue>,
     ) -> NeonResult<Result<Self, Self::Error>> {
-        Ok(serde_json::from_str(&stringify(cx, v)?)
-            .map(Json)
-            .map_err(Error))
+        let s = json_stringify(cx)?.call(cx, v, [v])?;
+        let res = match String::try_from_js(cx, s)? {
+            Ok(s) => serde_json::from_str(&s),
+            // If the type was not a `string`, it must be `undefined`
+            Err(_) => T::deserialize(serde::de::value::UnitDeserializer::new()),
+        };
+
+        Ok(res.map(Json).map_err(Error))
     }
 }
 

test/napi/lib/extract.js

@@ -73,6 +73,9 @@ describe("Extractors", () => {
   it("JSON", () => {
     assert.strictEqual(addon.extract_json_sum([1, 2, 3, 4]), 10);
     assert.strictEqual(addon.extract_json_sum([8, 16, 18]), 42);
+    assert.strictEqual(addon.extractJsonOption(42), 42);
+    assert.strictEqual(addon.extractJsonOption(null), null);
+    assert.strictEqual(addon.extractJsonOption(), null);
   });
 
   it("Either", () => {

test/napi/src/js/extract.rs

@@ -138,6 +138,11 @@ pub fn extract_single_add_one(mut cx: FunctionContext) -> JsResult<JsNumber> {
     Ok(cx.number(n + 1.0))
 }
 
+#[neon::export(json)]
+pub fn extract_json_option(maybe_x: Option<f64>) -> Option<f64> {
+    maybe_x
+}
+
 #[neon::export]
 pub fn extract_either(either: Either<String, f64>) -> String {
     match either {