Implement custom deserialization for custom scalars

Users of the library now have to provide type aliases for the scalars defined in the schema in the parent scope (the scope of the struct under derive).

Author: tomhoule

CHANGELOG.md

@@ -9,7 +9,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Added
 
-- Support for multi-operations documents. You can select a particular operation by naming the struct under derive after it.
+- (breaking) Control over which types custom scalars deserialize to is given to the user: you now have to provide type aliases for the custom scalars in the scope of the struct under derive.
+- (breaking) Support for multi-operations documents. You can select a particular operation by naming the struct under derive after it. In case there is no match, we revert to the current behaviour: select the first operation.
 
 ## [0.3.0] - 2018-07-24
 

examples/example_module/src/custom_scalars.rs

@@ -0,0 +1,10 @@
+//! We define the custom scalars present in the GitHub schema. More precise types could be provided here (see tests), as long as they are deserializable.
+
+pub type X509Certificate = String;
+pub type URI = String;
+pub type HTML = String;
+pub type GitTimestamp = String;
+pub type GitSSHRemote = String;
+pub type GitObjectID = String;
+pub type Date = String;
+pub type DateTime = String;

examples/example_module/src/lib.rs

@@ -4,6 +4,10 @@ extern crate serde_derive;
 #[macro_use]
 extern crate graphql_client;
 
+pub mod custom_scalars;
+
+use custom_scalars::*;
+
 #[derive(GraphQLQuery)]
 #[graphql(
     schema_path = "../github/src/schema.graphql",

examples/github/src/main.rs

@@ -20,6 +20,15 @@ extern crate prettytable;
 use graphql_client::*;
 use structopt::StructOpt;
 
+type X509Certificate = String;
+type URI = String;
+type HTML = String;
+type GitTimestamp = String;
+type GitSSHRemote = String;
+type GitObjectID = String;
+type Date = String;
+type DateTime = String;
+
 #[derive(GraphQLQuery)]
 #[graphql(
     schema_path = "src/schema.graphql",

graphql_query_derive/src/scalars.rs

@@ -15,6 +15,6 @@ impl Scalar {
             Some(d) => quote!(#[doc = #d]),
             None => quote!(),
         };
-        quote!(#description type #ident = String;)
+        quote!(#description type #ident = super::#ident;)
     }
 }

tests/custom_scalars.rs

@@ -0,0 +1,43 @@
+#[macro_use]
+extern crate graphql_client;
+extern crate serde;
+#[macro_use]
+extern crate serde_derive;
+#[macro_use]
+extern crate serde_json;
+
+use std::net::Ipv4Addr;
+
+// Important! The NetworkAddress scalar should deserialize to an Ipv4Addr from the Rust std library.
+type NetworkAddress = Ipv4Addr;
+
+#[derive(GraphQLQuery)]
+#[graphql(
+    query_path = "tests/custom_scalars/query.graphql",
+    schema_path = "tests/custom_scalars/schema.graphql"
+)]
+#[allow(dead_code)]
+struct CustomScalarsQuery;
+
+#[test]
+fn custom_scalars() {
+    let valid_response = json!({
+        "address": "127.0.1.2",
+    });
+
+    let valid_addr =
+        serde_json::from_value::<custom_scalars_query::ResponseData>(valid_response).unwrap();
+
+    assert_eq!(
+        valid_addr.address.unwrap(),
+        "127.0.1.2".parse::<Ipv4Addr>().unwrap()
+    );
+
+    let invalid_response = json!({
+        "address": "localhost",
+    });
+
+    assert!(
+        serde_json::from_value::<custom_scalars_query::ResponseData>(invalid_response).is_err()
+    );
+}

tests/custom_scalars/query.graphql

@@ -0,0 +1,3 @@
+query CustomScalarQuery {
+  address
+}

tests/custom_scalars/schema.graphql

@@ -0,0 +1,12 @@
+schema {
+  query: QueryRoot
+}
+
+"""
+An IPv4 address
+"""
+scalar NetworkAddress
+
+type QueryRoot {
+  address: NetworkAddress
+}

tests/input_object_variables.rs

@@ -27,6 +27,9 @@ fn input_object_variables_query_variables_struct() {
     };
 }
 
+// Custom scalars
+type Email = String;
+
 #[derive(GraphQLQuery)]
 #[graphql(
     query_path = "tests/input_object_variables/input_object_variables_query_defaults.graphql",