Add the DateTime<FixedOffset> scalar

src/scalars/datetime.rs

@@ -1,6 +1,23 @@
 use crate::{InputValueError, InputValueResult, ScalarType, Value};
 use async_graphql_derive::Scalar;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset, Utc};
+
+/// Implement the DateTime<FixedOffset> scalar
+///
+/// The input/output is a string in RFC3339 format.
+#[Scalar(internal, name = "DateTimeFixedOffset")]
+impl ScalarType for DateTime<FixedOffset> {
+    fn parse(value: Value) -> InputValueResult<Self> {
+        match &value {
+            Value::String(s) => Ok(DateTime::parse_from_rfc3339(s)?),
+            _ => Err(InputValueError::ExpectedType(value)),
+        }
+    }
+
+    fn to_value(&self) -> Value {
+        Value::String(self.to_rfc3339())
+    }
+}
 
 /// Implement the DateTime<Utc> scalar
 ///

src/scalars/mod.rs

@@ -25,7 +25,7 @@ mod tests {
     use super::ID;
     use crate::Type;
     use bson::oid::ObjectId;
-    use chrono::{DateTime, NaiveDate, NaiveTime, Utc};
+    use chrono::{DateTime, FixedOffset, NaiveDate, NaiveTime, Utc};
     use uuid::Uuid;
 
     #[test]
@@ -60,6 +60,15 @@ mod tests {
             "DateTimeUtc!"
         );
 
+        assert_eq!(
+            <DateTime::<FixedOffset> as Type>::type_name(),
+            "DateTimeFixedOffset"
+        );
+        assert_eq!(
+            <DateTime::<FixedOffset> as Type>::qualified_type_name(),
+            "DateTimeFixedOffset!"
+        );
+
         assert_eq!(<Uuid as Type>::type_name(), "UUID");
         assert_eq!(<Uuid as Type>::qualified_type_name(), "UUID!");