Introduce Decimal helper type

Author: adampetro

example/src/main.rs

@@ -59,7 +59,7 @@ fn function(input: input::ResponseData) -> Result<output::FunctionResult> {
             message: None,
             targets,
             value: output::Value::Percentage(output::Percentage {
-                value: config.percentage.to_string(),
+                value: Decimal(config.percentage),
             }),
         }],
         discount_application_strategy: output::DiscountApplicationStrategy::FIRST,

example/src/tests.rs

@@ -101,7 +101,7 @@ fn test_discount_with_configuration() -> Result<()> {
                 },
             )],
             value: crate::output::Value::Percentage(output::Percentage {
-                value: "10".to_string(),
+                value: Decimal(10.0),
             }),
         }],
         discount_application_strategy: crate::output::DiscountApplicationStrategy::FIRST,

shopify_function/src/scalars.rs

@@ -1,7 +1,9 @@
+mod decimal;
+
 pub type Boolean = bool;
 pub type Float = f64;
 pub type Int = i64;
 pub type ID = String;
-pub type Decimal = String;
+pub use decimal::Decimal;
 pub type Void = ();
 pub type URL = String;

shopify_function/src/scalars/decimal.rs

@@ -0,0 +1,62 @@
+use serde::{Deserialize, Serialize};
+use std::str::FromStr;
+
+/// Convenience wrapper for converting between Shopify's `Decimal` scalar, which
+/// is serialized as a `String`, and Rust's `f64`.
+#[derive(Deserialize, Serialize, Debug, PartialEq, Clone, Copy)]
+#[serde(try_from = "String")]
+#[serde(into = "String")]
+pub struct Decimal(pub f64);
+
+impl Decimal {
+    /// Access the value as an `f64`
+    pub fn as_f64(&self) -> f64 {
+        self.0
+    }
+}
+
+impl TryFrom<String> for Decimal {
+    type Error = std::num::ParseFloatError;
+
+    fn try_from(value: String) -> Result<Self, Self::Error> {
+        f64::from_str(value.as_str()).map(Self)
+    }
+}
+
+impl From<Decimal> for String {
+    fn from(value: Decimal) -> Self {
+        value.0.to_string()
+    }
+}
+
+impl From<Decimal> for f64 {
+    fn from(value: Decimal) -> Self {
+        value.0
+    }
+}
+
+impl From<f64> for Decimal {
+    fn from(value: f64) -> Self {
+        Self(value)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Decimal;
+
+    #[test]
+    fn test_json_deserialization() {
+        let decimal_value = serde_json::json!("123.4");
+        let decimal: Decimal =
+            serde_json::from_value(decimal_value).expect("Error deserializing from JSON");
+        assert_eq!(123.4, decimal.as_f64());
+    }
+
+    #[test]
+    fn test_json_serialization() {
+        let decimal = Decimal(123.4);
+        let json_value = serde_json::to_value(decimal).expect("Error serializing to JSON");
+        assert_eq!(serde_json::json!("123.4"), json_value);
+    }
+}

shopify_function_macro/src/lib.rs

@@ -350,8 +350,8 @@ fn generate_struct(name: &str, query_path: &str, schema_path: &str) -> TokenStre
         #[graphql(
             query_path = #query_path,
             schema_path = #schema_path,
-            response_derives = "Clone,Debug,PartialEq,Eq,Deserialize,Serialize",
-            variables_derives = "Clone,Debug,PartialEq,Eq,Deserialize",
+            response_derives = "Clone,Debug,PartialEq,Deserialize,Serialize",
+            variables_derives = "Clone,Debug,PartialEq,Deserialize",
             skip_serializing_none
         )]
         pub struct #name_ident;