Add StringNumber type.

Cargo.toml

@@ -14,10 +14,11 @@ categories = ["network-programming", "asynchronous"]
 readme = "README.md"
 
 [features]
-default = ["apollo_tracing", "uuid", "bson", "chrono", "chrono-tz", "log", "multipart", "tracing", "url", "unblock"]
+default = ["apollo_tracing", "uuid", "bson", "chrono", "chrono-tz", "log", "multipart", "tracing", "url", "unblock", "string_number"]
 apollo_tracing = ["chrono"]
 multipart = ["multer", "bytes", "tempfile"]
 unblock = ["blocking"]
+string_number = ["num-traits"]
 # Used for doc(cfg())
 nightly = []
 
@@ -47,6 +48,7 @@ chrono-tz = { version = "0.5.1", optional = true }
 log = { version = "0.4.11", optional = true }
 tracing = { version = "0.1.19", optional = true }
 url = { version = "2.1.1", optional = true }
+num-traits = { version = "0.2.12", optional = true }
 
 bytes = { version = "0.5.4", optional = true }
 multer = { version = "1.2.2", optional = true }

src/types/mod.rs

@@ -10,6 +10,8 @@ mod json;
 mod maybe_undefined;
 mod merged_object;
 mod query_root;
+#[cfg(feature = "string_number")]
+mod string_number;
 mod upload;
 
 mod external;
@@ -21,6 +23,8 @@ pub use id::ID;
 pub use json::{Json, OutputJson};
 pub use maybe_undefined::MaybeUndefined;
 pub use merged_object::{MergedObject, MergedObjectSubscriptionTail, MergedObjectTail};
+#[cfg(feature = "string_number")]
+pub use string_number::StringNumber;
 pub use upload::Upload;
 
 pub(crate) use query_root::QueryRoot;

src/types/string_number.rs

@@ -0,0 +1,78 @@
+use crate::{InputValueError, InputValueResult, Scalar, ScalarType, Value};
+use num_traits::Num;
+use serde::{Deserialize, Serialize};
+use std::fmt::Display;
+
+/// A numeric value represented by a string.
+#[derive(Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
+#[serde(transparent)]
+#[cfg_attr(feature = "nightly", doc(cfg(feature = "string_number")))]
+pub struct StringNumber<T: Num + Display>(pub T);
+
+#[Scalar(internal)]
+impl<T: Num + Display + Send + Sync> ScalarType for StringNumber<T>
+where
+    <T as Num>::FromStrRadixErr: Display,
+{
+    fn parse(value: Value) -> InputValueResult<Self> {
+        match value {
+            Value::String(s) => {
+                let n = T::from_str_radix(&s, 10)
+                    .map_err(|err| InputValueError::Custom(err.to_string()))?;
+                Ok(StringNumber(n))
+            }
+            _ => Err(InputValueError::ExpectedType(value)),
+        }
+    }
+
+    fn is_valid(value: &Value) -> bool {
+        match value {
+            Value::String(_) => true,
+            _ => false,
+        }
+    }
+
+    fn to_value(&self) -> Value {
+        Value::String(self.0.to_string())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::*;
+
+    #[async_std::test]
+    async fn test_string_number() {
+        struct Query;
+
+        #[Object(internal)]
+        impl Query {
+            async fn value(&self, n: StringNumber<i32>) -> StringNumber<i32> {
+                n
+            }
+        }
+
+        let schema = Schema::new(Query, EmptyMutation, EmptySubscription);
+        assert_eq!(
+            schema
+                .execute(
+                    r#"{
+                    value1: value(n: "100")
+                    value2: value(n: "-100")
+                    value3: value(n: "0")
+                    value4: value(n: "1")
+                }"#
+                )
+                .await
+                .into_result()
+                .unwrap()
+                .data,
+            serde_json::json!({
+                "value1": "100",
+                "value2": "-100",
+                "value3": "0",
+                "value4": "1",
+            })
+        );
+    }
+}