Add special handling for dates behind feature flag

Cargo.toml

@@ -44,3 +44,6 @@ debug = true
 
 [patch.crates-io]
 proptest = { git = "https://github.com/RReverser/proptest", branch = "fix-wasm" }
+
+[features]
+special-dates = []

src/de.rs

@@ -1,8 +1,9 @@
-use js_sys::{Array, ArrayBuffer, JsString, Number, Object, Symbol, Uint8Array};
+use js_sys::{Array, ArrayBuffer, Date, JsString, Number, Object, Symbol, Uint8Array};
 use serde::de::value::{MapDeserializer, SeqDeserializer};
 use serde::de::{self, IntoDeserializer};
 use std::convert::TryFrom;
 use wasm_bindgen::{JsCast, JsValue, UnwrapThrowExt};
+use crate::SPECIAL_DATE_PREFIX;
 
 use super::{static_str_to_js, Error, ObjectExt, Result};
 
@@ -291,7 +292,19 @@ impl<'de> de::Deserializer<'de> for Deserializer {
             // https://github.com/serde-rs/serde/issues/1183 is implemented / fixed on serde side.
             !Symbol::iterator().js_in(&self.value)
         {
-            self.deserialize_map(visitor)
+            // `Date` gets deserialized to an empty object, which is pretty useless.
+            // special case to be an ISO string
+            if cfg!(feature = "special-dates") {
+                match self.value.dyn_ref::<Date>() {
+                    Some(date) => {
+                        let iso_string = date.to_iso_string().as_string().expect_throw("to_iso_string returns a valid string");
+                        visitor.visit_string(format!("{}{}", SPECIAL_DATE_PREFIX, iso_string))
+                    }
+                    None => self.deserialize_map(visitor)
+                }
+            } else {
+                self.deserialize_map(visitor)
+            }
         } else {
             self.invalid_type(visitor)
         }

src/lib.rs

@@ -13,6 +13,8 @@ pub use de::Deserializer;
 pub use error::Error;
 pub use ser::Serializer;
 
+pub(crate) const SPECIAL_DATE_PREFIX: &'static str = "$::date:";
+
 type Result<T> = std::result::Result<T, Error>;
 
 fn static_str_to_js(s: &'static str) -> JsString {

src/ser.rs

@@ -2,6 +2,7 @@ use js_sys::{Array, JsString, Map, Number, Object, Uint8Array};
 use serde::ser::{self, Error as _, Serialize};
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
+use crate::SPECIAL_DATE_PREFIX;
 
 use super::{static_str_to_js, Error, ObjectExt};
 
@@ -308,10 +309,10 @@ impl<'s> ser::Serializer for &'s Serializer {
 
         serialize_f32(f32);
         serialize_f64(f64);
-
-        serialize_str(&str);
     }
 
+
+
     fn serialize_i64(self, v: i64) -> Result {
         if self.serialize_large_number_types_as_bigints {
             return Ok(v.into());
@@ -473,4 +474,18 @@ impl<'s> ser::Serializer for &'s Serializer {
             self.serialize_struct(variant, len)?,
         ))
     }
+
+    fn serialize_str(self, v: &str) -> Result {
+        if cfg!(feature = "special-dates") {
+            match v.strip_prefix(SPECIAL_DATE_PREFIX) {
+                Some(v) => {
+                    let date = js_sys::Date::new(&v.into());
+                    Ok(date.into())
+                }
+                None => Ok(v.into())
+            }
+        } else {
+            Ok(v.into())
+        }
+    }
 }

tests/common/mod.rs

@@ -819,3 +819,22 @@ fn serde_default_fields() {
     // Check that it parses successfully despite the missing field.
     let _struct: Struct = from_value(obj).unwrap();
 }
+
+#[test]
+#[cfg(feature = "special-dates")]
+fn dates_are_serialized_as_strings() {
+    let date = js_sys::Date::new_0();
+    let object = Object::new();
+    js_sys::Reflect::set(&object, &"date".into(), &date).unwrap();
+    let value = object.into();
+    let mut value: serde_json::Value = from_value(value).unwrap();
+
+    let obj = value.as_object_mut().unwrap();
+    obj.insert("anotherValue".to_string(), serde_json::Value::String("something".to_string()));
+    assert!(obj.get("date").unwrap().as_str().unwrap().starts_with("$::date:"));
+
+    let to_value = value.serialize(&Serializer::json_compatible()).unwrap();
+    let date = js_sys::Reflect::get(&to_value, &"date".into()).unwrap();
+    assert!(date.dyn_into::<js_sys::Date>().is_ok())
+
+}