From 8370001272a180c8554f35c9a509e4baf5ead365 Mon Sep 17 00:00:00 2001
From: Sunli <scott_s829@163.com>
Date: Sun, 8 Nov 2020 09:22:50 +0800
Subject: [PATCH] Implements Cow<T> for OutputValueType. #189

---
 src/base.rs                  |   4 +-
 src/types/external/cow.rs    | 101 +++++++++++++++++++++++++++++++++++
 src/types/external/mod.rs    |   1 +
 src/types/external/string.rs |   6 +--
 4 files changed, 107 insertions(+), 5 deletions(-)
 create mode 100644 src/types/external/cow.rs

diff --git a/src/base.rs b/src/base.rs
index 88c4bdde..ab83ad62 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -55,7 +55,7 @@ pub trait OutputValueType: Type {
     ) -> ServerResult<Value>;
 }
 
-impl<T: Type + Send + Sync> Type for &T {
+impl<T: Type + Send + Sync + ?Sized> Type for &T {
     fn type_name() -> Cow<'static, str> {
         T::type_name()
     }
@@ -66,7 +66,7 @@ impl<T: Type + Send + Sync> Type for &T {
 }
 
 #[async_trait::async_trait]
-impl<T: OutputValueType + Send + Sync> OutputValueType for &T {
+impl<T: OutputValueType + Send + Sync + ?Sized> OutputValueType for &T {
     #[allow(clippy::trivially_copy_pass_by_ref)]
     async fn resolve(
         &self,
diff --git a/src/types/external/cow.rs b/src/types/external/cow.rs
new file mode 100644
index 00000000..71921e6a
--- /dev/null
+++ b/src/types/external/cow.rs
@@ -0,0 +1,101 @@
+use std::borrow::Cow;
+
+use crate::{
+    registry, ContextSelectionSet, OutputValueType, Positioned, ServerResult, Type, Value,
+};
+use async_graphql_parser::types::Field;
+
+impl<'a, T> Type for Cow<'a, T>
+where
+    T: Type + ToOwned + ?Sized + Send + Sync,
+{
+    fn type_name() -> Cow<'static, str> {
+        T::type_name()
+    }
+
+    fn create_type_info(registry: &mut registry::Registry) -> String {
+        <T as Type>::create_type_info(registry)
+    }
+}
+
+#[async_trait::async_trait]
+impl<'a, T> OutputValueType for Cow<'a, T>
+where
+    T: OutputValueType + ToOwned + ?Sized + Send + Sync,
+    <T as ToOwned>::Owned: Send + Sync,
+{
+    async fn resolve(
+        &self,
+        ctx: &ContextSelectionSet<'_>,
+        field: &Positioned<Field>,
+    ) -> ServerResult<Value> {
+        self.as_ref().resolve(ctx, field).await
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::*;
+    use std::borrow::Cow;
+
+    #[async_std::test]
+    async fn test_cow_type() {
+        struct Query11 {
+            obj: MyObj,
+        }
+
+        #[derive(SimpleObject, Clone)]
+        #[graphql(internal)]
+        struct MyObj {
+            a: i32,
+            b: i32,
+        }
+
+        #[Object(internal)]
+        impl Query11 {
+            async fn value1(&self) -> Cow<'_, str> {
+                Cow::Borrowed("abc")
+            }
+
+            async fn value2(&self) -> Cow<'_, str> {
+                Cow::Owned("def".to_string())
+            }
+
+            async fn obj1(&self) -> Cow<'_, MyObj> {
+                Cow::Borrowed(&self.obj)
+            }
+
+            async fn obj2(&self) -> Cow<'_, MyObj> {
+                Cow::Owned(MyObj { a: 300, b: 400 })
+            }
+        }
+
+        let query = r#"{
+            value1
+            value2
+            obj1 {
+                a b
+            }
+            obj2 {
+                a b
+            }
+        }"#;
+        let schema = Schema::new(
+            Query11 {
+                obj: MyObj { a: 100, b: 200 },
+            },
+            EmptyMutation,
+            EmptySubscription,
+        );
+
+        assert_eq!(
+            schema.execute(query).await.into_result().unwrap().data,
+            value!({
+             "value1": "abc",
+             "value2": "def",
+             "obj1": {"a": 100, "b": 200},
+             "obj2": {"a": 300, "b": 400},
+            })
+        );
+    }
+}
diff --git a/src/types/external/mod.rs b/src/types/external/mod.rs
index 4962f44c..e1c5dac4 100644
--- a/src/types/external/mod.rs
+++ b/src/types/external/mod.rs
@@ -2,6 +2,7 @@
 
 mod bool;
 mod char;
+mod cow;
 mod floats;
 mod integers;
 mod json_object;
diff --git a/src/types/external/string.rs b/src/types/external/string.rs
index 98655aa5..cfd766f5 100644
--- a/src/types/external/string.rs
+++ b/src/types/external/string.rs
@@ -25,7 +25,7 @@ impl ScalarType for String {
     }
 }
 
-impl<'a> Type for &'a str {
+impl Type for str {
     fn type_name() -> Cow<'static, str> {
         Cow::Borrowed("String")
     }
@@ -36,12 +36,12 @@ impl<'a> Type for &'a str {
 }
 
 #[async_trait::async_trait]
-impl<'a> OutputValueType for &'a str {
+impl OutputValueType for str {
     async fn resolve(
         &self,
         _: &ContextSelectionSet<'_>,
         _field: &Positioned<Field>,
     ) -> ServerResult<Value> {
-        Ok(Value::String((*self).to_string()))
+        Ok(Value::String(self.to_string()))
     }
 }