From d280a13b708260ce39ba573264ff33e2bbd96f27 Mon Sep 17 00:00:00 2001
From: Sunli <scott_s829@163.com>
Date: Mon, 10 Aug 2020 14:11:46 +0800
Subject: [PATCH] Add derive macro GQLMergeObject. #231

---
 async-graphql-derive/src/lib.rs           | 18 ++++++++++--
 async-graphql-derive/src/merged_object.rs | 36 +++++------------------
 src/base.rs                               |  7 +++++
 src/lib.rs                                |  5 +++-
 tests/merged_object.rs                    | 30 ++++++++++++++++++-
 5 files changed, 64 insertions(+), 32 deletions(-)

diff --git a/async-graphql-derive/src/lib.rs b/async-graphql-derive/src/lib.rs
index a8c4e550..3f808b59 100644
--- a/async-graphql-derive/src/lib.rs
+++ b/async-graphql-derive/src/lib.rs
@@ -19,7 +19,7 @@ mod utils;
 use crate::utils::{add_container_attrs, parse_derive};
 use proc_macro::TokenStream;
 use quote::quote;
-use syn::{parse_macro_input, DeriveInput};
+use syn::parse_macro_input;
 use syn::{AttributeArgs, ItemImpl};
 
 #[proc_macro_attribute]
@@ -207,11 +207,25 @@ pub fn Scalar(args: TokenStream, input: TokenStream) -> TokenStream {
 #[proc_macro_attribute]
 #[allow(non_snake_case)]
 pub fn MergedObject(args: TokenStream, input: TokenStream) -> TokenStream {
+    add_container_attrs(
+        quote!(GQLMergedObject),
+        parse_macro_input!(args as AttributeArgs),
+        input.into(),
+    )
+    .unwrap_or_else(|err| err.to_compile_error())
+    .into()
+}
+
+#[proc_macro_derive(GQLMergedObject, attributes(item, graphql))]
+pub fn derive_merged_object(input: TokenStream) -> TokenStream {
+    let (args, input) = match parse_derive(input.into()) {
+        Ok(r) => r,
+        Err(err) => return err.to_compile_error().into(),
+    };
     let object_args = match args::Object::parse(parse_macro_input!(args as AttributeArgs)) {
         Ok(object_args) => object_args,
         Err(err) => return err.to_compile_error().into(),
     };
-    let input = parse_macro_input!(input as DeriveInput);
     match merged_object::generate(&object_args, &input) {
         Ok(expanded) => expanded,
         Err(err) => err.to_compile_error().into(),
diff --git a/async-graphql-derive/src/merged_object.rs b/async-graphql-derive/src/merged_object.rs
index ed16ca9e..3dfb8c0c 100644
--- a/async-graphql-derive/src/merged_object.rs
+++ b/async-graphql-derive/src/merged_object.rs
@@ -1,9 +1,9 @@
 use crate::args;
 use crate::utils::{get_crate_name, get_rustdoc};
 use proc_macro::TokenStream;
+use proc_macro2::Span;
 use quote::quote;
-use syn::spanned::Spanned;
-use syn::{Data, DeriveInput, Error, Ident, Result};
+use syn::{Data, DeriveInput, Error, LitInt, Result};
 
 pub fn generate(object_args: &args::Object, input: &DeriveInput) -> Result<TokenStream> {
     let crate_name = get_crate_name(object_args.internal);
@@ -13,8 +13,6 @@ pub fn generate(object_args: &args::Object, input: &DeriveInput) -> Result<Token
         .name
         .clone()
         .unwrap_or_else(|| ident.to_string());
-    let vis = &input.vis;
-    let attrs = &input.attrs;
 
     let desc = object_args
         .desc
@@ -33,23 +31,14 @@ pub fn generate(object_args: &args::Object, input: &DeriveInput) -> Result<Token
         types.push(&field.ty);
     }
 
-    let new_args = {
-        let mut new_args = Vec::new();
-        for (i, ty) in types.iter().enumerate() {
-            let name = Ident::new(&format!("obj{}", i + 1), ty.span());
-            new_args.push(quote! { #name: #ty })
-        }
-        new_args
-    };
-
-    let new_func = {
+    let create_merged_obj = {
         let mut obj = quote! { #crate_name::MergedObjectTail };
-        for (i, ty) in types.iter().enumerate() {
-            let name = Ident::new(&format!("obj{}", i + 1), ty.span());
-            obj = quote! { #crate_name::MergedObject(#name, #obj) };
+        for i in 0..types.len() {
+            let n = LitInt::new(&format!("{}", i), Span::call_site());
+            obj = quote! { #crate_name::MergedObject(&self.#n, #obj) };
         }
         quote! {
-            Self(#obj)
+            #obj
         }
     };
 
@@ -62,15 +51,6 @@ pub fn generate(object_args: &args::Object, input: &DeriveInput) -> Result<Token
     };
 
     let expanded = quote! {
-        #(#attrs)*
-        #vis struct #ident(#merged_type);
-
-        impl #ident {
-            pub fn new(#(#new_args),*) -> Self {
-                #new_func
-            }
-        }
-
         #[allow(clippy::all, clippy::pedantic)]
         impl #crate_name::Type for #ident {
             fn type_name() -> ::std::borrow::Cow<'static, str> {
@@ -109,7 +89,7 @@ pub fn generate(object_args: &args::Object, input: &DeriveInput) -> Result<Token
         #[#crate_name::async_trait::async_trait]
         impl #crate_name::ObjectType for #ident {
             async fn resolve_field(&self, ctx: &#crate_name::Context<'_>) -> #crate_name::Result<#crate_name::serde_json::Value> {
-                self.0.resolve_field(ctx).await
+                #create_merged_obj.resolve_field(ctx).await
             }
         }
 
diff --git a/src/base.rs b/src/base.rs
index 7c3690d7..72062d07 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -166,6 +166,13 @@ impl<T: OutputValueType + Send + Sync> OutputValueType for &T {
     }
 }
 
+#[async_trait::async_trait]
+impl<T: ObjectType + Send + Sync> ObjectType for &T {
+    async fn resolve_field(&self, ctx: &Context<'_>) -> Result<serde_json::Value> {
+        T::resolve_field(*self, ctx).await
+    }
+}
+
 impl<T: Type + Send + Sync> Type for Box<T> {
     fn type_name() -> Cow<'static, str> {
         T::type_name()
diff --git a/src/lib.rs b/src/lib.rs
index 90fc433b..63218238 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -786,6 +786,9 @@ pub use async_graphql_derive::Scalar;
 /// #[MergedObject]
 /// struct MyObj(Object1, Object2, Object3);
 ///
-/// let obj = MyObj::new(Object1 { a: 10 }, Object2 { b: 20 }, Object3 { c: 30 });
+/// let obj = MyObj(Object1 { a: 10 }, Object2 { b: 20 }, Object3 { c: 30 });
 /// ```
 pub use async_graphql_derive::MergedObject;
+
+/// Derive a GraphQL Merged object
+pub use async_graphql_derive::GQLMergedObject;
diff --git a/tests/merged_object.rs b/tests/merged_object.rs
index da73f7ff..c855c022 100644
--- a/tests/merged_object.rs
+++ b/tests/merged_object.rs
@@ -64,7 +64,35 @@ pub async fn test_merged_object_macro() {
     #[Object]
     impl Query {
         async fn obj(&self) -> MyObj {
-            MyObj::new(Object1 { a: 10 }, Object2 { b: 20 }, Object3 { c: 30 })
+            MyObj(Object1 { a: 10 }, Object2 { b: 20 }, Object3 { c: 30 })
+        }
+    }
+
+    let schema = Schema::new(Query, EmptyMutation, EmptySubscription);
+    let query = "{ obj { a b c } }";
+    assert_eq!(
+        schema.execute(&query).await.unwrap().data,
+        serde_json::json!({
+            "obj": {
+                "a": 10,
+                "b": 20,
+                "c": 30,
+            }
+        })
+    );
+}
+
+#[async_std::test]
+pub async fn test_merged_object_derive() {
+    #[derive(GQLMergedObject)]
+    struct MyObj(Object1, Object2, Object3);
+
+    struct Query;
+
+    #[Object]
+    impl Query {
+        async fn obj(&self) -> MyObj {
+            MyObj(Object1 { a: 10 }, Object2 { b: 20 }, Object3 { c: 30 })
         }
     }