feat: add chrono::Duration custom scalar

Cargo.toml

@@ -22,6 +22,7 @@ dataloader = ["futures-timer", "futures-channel", "lru"]
 tracing = ["tracinglib", "tracing-futures"]
 decimal = ["rust_decimal"]
 cbor = ["serde_cbor"]
+chrono-duration = ["chrono", "iso8601-duration"]
 
 [dependencies]
 async-graphql-derive = { path = "derive", version = "=2.11.0" }
@@ -50,6 +51,7 @@ mime = "0.3.15"
 bson = { version = "2.0.0", optional = true, features = ["chrono-0_4"] }
 chrono = { version = "0.4.19", optional = true }
 chrono-tz = { version = "0.5.3", optional = true }
+iso8601-duration = { version = "0.1.0", optional = true }
 log = { version = "0.4.14", optional = true }
 secrecy = { version = "0.7.0", optional = true }
 tracinglib = { version = "0.1.25", optional = true, package = "tracing" }

src/types/external/duration.rs

@@ -0,0 +1,21 @@
+use chrono::Duration;
+use iso8601_duration as iso8601;
+
+use crate::{InputValueError, InputValueResult, Scalar, ScalarType, Value};
+
+/// Implement the Duration scalar
+///
+/// The input/output is a string in ISO8601 format.
+#[Scalar(internal, name = "Duration", specified_by_url = "https://en.wikipedia.org/wiki/ISO_8601#Durations")]
+impl ScalarType for Duration {
+    fn parse(value: Value) -> InputValueResult<Self> {
+        match &value {
+            Value::String(s) => Ok(Duration::from_std(iso8601::Duration::parse(s)?.to_std())?),
+            _ => Err(InputValueError::expected_type(value)),
+        }
+    }
+
+    fn to_value(&self) -> Value {
+        Value::String(self.to_string())
+    }
+}

src/types/external/mod.rs

@@ -18,6 +18,8 @@ mod bson;
 mod chrono_tz;
 #[cfg(feature = "chrono")]
 mod datetime;
+#[cfg(feature = "chrono-duration")]
+mod duration;
 #[cfg(feature = "decimal")]
 mod decimal;
 #[cfg(feature = "chrono")]