Add the ability to use $args and $this in headers

apollo-federation/src/sources/connect/header.rs

@@ -113,7 +113,12 @@ fn identifier(input: &str) -> IResult<&str, &str> {
 }
 
 fn namespace(input: &str) -> IResult<&str, &str> {
-    recognize(alt((tag("$config"), tag("$context"))))(input)
+    recognize(alt((
+        tag("$args"),
+        tag("$config"),
+        tag("$context"),
+        tag("$this"),
+    )))(input)
 }
 
 fn path(input: &str) -> IResult<&str, &str> {

apollo-router/src/plugins/connectors/testdata/steelthread.graphql

@@ -73,7 +73,7 @@ type Query
 {
   users: [User] @join__field(graph: CONNECTORS) @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/users", headers: [{name: "x-new-name", from: "x-rename-connect"}, {name: "x-insert-multi-value", value: "first,second"}, {name: "x-config-variable-connect", value: "before {$config.connect.val} after"}, {name: "x-context-value-connect", value: "before {$context.val} after"}]}, selection: "id name"})
   me: User @join__field(graph: CONNECTORS) @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/users/{$config.id}"}, selection: "id\nname\nusername"})
-  user(id: ID!): User @join__field(graph: CONNECTORS) @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/users/{$args.id}"}, selection: "id\nname\nusername", entity: true})
+  user(id: ID!): User @join__field(graph: CONNECTORS) @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/users/{$args.id}", headers: [{name: "x-from-args", value: "before {$args.id} after"}]}, selection: "id\nname\nusername", entity: true})
   posts: [Post] @join__field(graph: CONNECTORS) @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/posts"}, selection: "id title user: { id: userId }"})
 }
 
@@ -84,6 +84,7 @@ type User
   id: ID!
   name: String @join__field(graph: CONNECTORS)
   username: String @join__field(graph: CONNECTORS)
+  nickname: String @join__field(graph: CONNECTORS) @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/users/{$this.id}/nicknames", headers: [{name: "x-from-this", value: "before {$this.id} after"}]}, selection: "nickname: $.first"})
   c: String @join__field(graph: CONNECTORS, external: true) @join__field(graph: GRAPHQL)
   d: String @join__field(graph: CONNECTORS, requires: "c") @join__directive(graphs: [CONNECTORS], name: "connect", args: {source: "json", http: {GET: "/users/{$this.c}"}, selection: "$.phone"})
 }

apollo-router/src/plugins/connectors/testdata/steelthread.yaml

@@ -1,5 +1,5 @@
 # rover supergraph compose --config apollo-router/src/plugins/connectors/testdata/steelthread.yaml > apollo-router/src/plugins/connectors/testdata/steelthread.graphql
-federation_version: =2.10.0-alpha.0
+federation_version: =2.10.0-preview.0
 subgraphs:
   connectors:
     routing_url: none
@@ -57,7 +57,12 @@ subgraphs:
           user(id: ID!): User
             @connect(
               source: "json"
-              http: { GET: "/users/{$$args.id}" }
+              http: {
+                GET: "/users/{$$args.id}"
+                headers: [
+                 {name: "x-from-args" value: "before {$$args.id} after"}
+                ]
+              }
               selection: """
               id
               name
@@ -78,6 +83,17 @@ subgraphs:
           id: ID!
           name: String
           username: String
+          nickname: String
+            @connect(
+              source: "json"
+              http: {
+                GET: "/users/{$$this.id}/nicknames"
+                headers: [
+                 {name: "x-from-this" value: "before {$$this.id} after"}
+                ]
+              }
+              selection: "$.first"
+            )
           c: String @external
           d: String
             @requires(fields: "c")

apollo-router/src/plugins/connectors/tests.rs

@@ -84,6 +84,12 @@ pub(crate) mod mock_api {
         )
     }
 
+    pub(crate) fn user_2_nicknames() -> Mock {
+        Mock::given(method("GET"))
+            .and(path("/users/2/nicknames"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!(["cat"])))
+    }
+
     pub(crate) fn users_error() -> Mock {
         Mock::given(method("GET")).and(path("/users")).respond_with(
             ResponseTemplate::new(404).set_body_json(serde_json::json!([
@@ -668,6 +674,45 @@ async fn test_headers() {
     );
 }
 
+#[tokio::test]
+async fn test_args_and_this_in_header() {
+    let mock_server = MockServer::start().await;
+    mock_api::user_2().mount(&mock_server).await;
+    mock_api::user_2_nicknames().mount(&mock_server).await;
+
+    execute(
+        STEEL_THREAD_SCHEMA,
+        &mock_server.uri(),
+        "query { user(id: 2){ id nickname } }",
+        Default::default(),
+        None,
+        |_| {},
+    )
+    .await;
+
+    req_asserts::matches(
+        &mock_server.received_requests().await.unwrap(),
+        vec![
+            Matcher::new()
+                .method("GET")
+                .header(
+                    HeaderName::from_str("x-from-args").unwrap(),
+                    HeaderValue::from_str("before 2 after").unwrap(),
+                )
+                .path("/users/2")
+                .build(),
+            Matcher::new()
+                .method("GET")
+                .header(
+                    HeaderName::from_str("x-from-this").unwrap(),
+                    HeaderValue::from_str("before 2 after").unwrap(),
+                )
+                .path("/users/2/nicknames")
+                .build(),
+        ],
+    );
+}
+
 mock! {
     Subscriber {}
     impl tracing_core::Subscriber for Subscriber {