From f24c6fceffdf97383cc15f6ed28959d243079b00 Mon Sep 17 00:00:00 2001
From: sunli <scott_s829@163.com>
Date: Sat, 9 May 2020 18:34:57 +0800
Subject: [PATCH] Add ability to forward field arguments to guard #59

---
 async-graphql-derive/src/object.rs       |  2 +-
 async-graphql-derive/src/subscription.rs |  5 +-
 async-graphql-derive/src/utils.rs        | 10 +++-
 tests/guard.rs                           | 58 ++++++++++++++++++++++++
 4 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/async-graphql-derive/src/object.rs b/async-graphql-derive/src/object.rs
index 44e9e2bd..10996926 100644
--- a/async-graphql-derive/src/object.rs
+++ b/async-graphql-derive/src/object.rs
@@ -387,8 +387,8 @@ pub fn generate(object_args: &args::Object, item_impl: &mut ItemImpl) -> Result<
                 resolvers.push(quote! {
                     if ctx.name.as_str() == #field_name {
                         use #crate_name::OutputValueType;
-                        #guard
                         #(#get_params)*
+                        #guard
                         let ctx_obj = ctx.with_selection_set(&ctx.selection_set);
                         return OutputValueType::resolve(&#resolve_obj, &ctx_obj, ctx.position()).await;
                     }
diff --git a/async-graphql-derive/src/subscription.rs b/async-graphql-derive/src/subscription.rs
index d4ab6550..825ebfcf 100644
--- a/async-graphql-derive/src/subscription.rs
+++ b/async-graphql-derive/src/subscription.rs
@@ -238,10 +238,9 @@ pub fn generate(object_args: &args::Object, item_impl: &mut ItemImpl) -> Result<
                     if ctx.name.as_str() == #field_name {
                         use #crate_name::futures::stream::{StreamExt, TryStreamExt};
 
-                        #guard
-
-                        let field_name = std::sync::Arc::new(ctx.result_name().to_string());
                         #(#get_params)*
+                        #guard
+                        let field_name = std::sync::Arc::new(ctx.result_name().to_string());
                         let field_selection_set = std::sync::Arc::new(ctx.selection_set.clone());
                         let schema = schema.clone();
                         let pos = ctx.position();
diff --git a/async-graphql-derive/src/utils.rs b/async-graphql-derive/src/utils.rs
index d1860fed..22fbd00e 100644
--- a/async-graphql-derive/src/utils.rs
+++ b/async-graphql-derive/src/utils.rs
@@ -196,8 +196,14 @@ pub fn parse_guards(crate_name: &TokenStream, args: &MetaList) -> Result<Option<
                             if let NestedMeta::Meta(Meta::NameValue(nv)) = attr {
                                 let name = &nv.path;
                                 if let Lit::Str(value) = &nv.lit {
-                                    let expr = syn::parse_str::<Expr>(&value.value())?;
-                                    params.push(quote! { #name: #expr.into() });
+                                    let value_str = value.value();
+                                    if value_str.starts_with('@') {
+                                        let id = Ident::new(&value_str[1..], value.span());
+                                        params.push(quote! { #name: &#id });
+                                    } else {
+                                        let expr = syn::parse_str::<Expr>(&value_str)?;
+                                        params.push(quote! { #name: #expr.into() });
+                                    }
                                 } else {
                                     return Err(Error::new_spanned(
                                         &nv.lit,
diff --git a/tests/guard.rs b/tests/guard.rs
index fb6efbe9..666ff882 100644
--- a/tests/guard.rs
+++ b/tests/guard.rs
@@ -317,3 +317,61 @@ pub async fn test_multiple_guards() {
         }
     );
 }
+
+#[async_std::test]
+pub async fn test_guard_forward_arguments() {
+    struct UserGuard<'a> {
+        id: &'a ID,
+    }
+
+    #[async_trait::async_trait]
+    impl<'a> Guard for UserGuard<'a> {
+        async fn check(&self, ctx: &Context<'_>) -> FieldResult<()> {
+            if ctx.data_opt::<ID>() != Some(self.id) {
+                Err("Forbidden".into())
+            } else {
+                Ok(())
+            }
+        }
+    }
+
+    struct QueryRoot;
+
+    #[Object]
+    impl QueryRoot {
+        #[field(guard(UserGuard(id = "@id")))]
+        async fn user(&self, id: ID) -> ID {
+            id
+        }
+    }
+
+    let schema = Schema::new(QueryRoot, EmptyMutation, EmptySubscription);
+
+    let query = r#"{ user(id: "abc") }"#;
+    assert_eq!(
+        QueryBuilder::new(query)
+            .data(ID::from("abc"))
+            .execute(&schema)
+            .await
+            .unwrap()
+            .data,
+        serde_json::json!({"user": "abc"})
+    );
+
+    let query = r#"{ user(id: "abc") }"#;
+    assert_eq!(
+        QueryBuilder::new(query)
+            .data(ID::from("aaa"))
+            .execute(&schema)
+            .await
+            .unwrap_err(),
+        Error::Query {
+            pos: Pos { line: 1, column: 3 },
+            path: Some(serde_json::json!(["user"])),
+            err: QueryError::FieldError {
+                err: "Forbidden".to_string(),
+                extended_error: None,
+            },
+        }
+    );
+}