Feat/fix: Adding signature validation to the "hook" option so the error is clear if users try to use an invalid function as a hook. Also fixing the request_hook trybuild test, which was not actually testing anything

Author: JeremieRodon

lambda-appsync-proc/src/appsync_lambda_main/mod.rs

@@ -307,7 +307,19 @@ impl AppsyncLambdaMain {
     fn appsync_event_handler(&self, tokens: &mut TokenStream2) {
         let call_hook = if let Some(ref hook) = self.options.hook {
             quote_spanned! {hook.span()=>
-                if let Some(resp) = #hook(&event).await {
+                mod _check_sig {
+                    use super::Operation;
+                    use ::lambda_appsync::{AppsyncEvent, AppsyncResponse};
+                    use ::core::future::Future;
+                    #[inline(always)]
+                    pub(super) async fn call_hook<'a, Fut, H>(hook: H, event: &'a AppsyncEvent<Operation>) -> Option<AppsyncResponse>
+                    where
+                        Fut: Future<Output = Option<AppsyncResponse>>,
+                        H: Fn(&'a AppsyncEvent<Operation>) -> Fut {
+                        hook(event).await
+                    }
+                }
+                if let Some(resp) = _check_sig::call_hook(#hook, &event).await{
                     return resp;
                 }
             }

lambda-appsync-proc/tests/fail/invalid_hook_args.rs

@@ -0,0 +1,9 @@
+mod no_run {
+    use lambda_appsync::{appsync_lambda_main, AppsyncResponse};
+    async fn verify_request(_event: &Operation) -> Option<AppsyncResponse> {
+        None // Allow all requests
+    }
+    appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+}
+
+fn main() {}

lambda-appsync-proc/tests/fail/invalid_hook_args.stderr

@@ -0,0 +1,20 @@
+error[E0631]: type mismatch in function arguments
+ --> tests/fail/invalid_hook_args.rs:6:63
+  |
+3 |     async fn verify_request(_event: &Operation) -> Option<AppsyncResponse> {
+  |     ---------------------------------------------------------------------- found signature defined here
+...
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+  |                                                               ^^^^^^^^^^^^^^ expected due to this
+  |
+  = note: expected function signature `fn(&AppsyncEvent<no_run::Operation>) -> _`
+             found function signature `fn(&no_run::Operation) -> _`
+note: required by a bound in `call_hook`
+ --> tests/fail/invalid_hook_args.rs:6:63
+  |
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+  |                                                               ^^^^^^^^^^^^^^ required by this bound in `call_hook`
+help: consider wrapping the function in a closure
+  |
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = |arg0: &AppsyncEvent<no_run::Operation>| verify_request(/* &no_run::Operation */));
+  |                                                               ++++++++++++++++++++++++++++++++++++++++               ++++++++++++++++++++++++++

lambda-appsync-proc/tests/fail/invalid_hook_no_async.rs

@@ -0,0 +1,9 @@
+mod no_run {
+    use lambda_appsync::{appsync_lambda_main, AppsyncEvent, AppsyncResponse};
+    fn verify_request(_event: &AppsyncEvent<Operation>) -> Option<AppsyncResponse> {
+        None // Allow all requests
+    }
+    appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+}
+
+fn main() {}

lambda-appsync-proc/tests/fail/invalid_hook_no_async.stderr

@@ -0,0 +1,12 @@
+error[E0277]: `std::option::Option<AppsyncResponse>` is not a future
+ --> tests/fail/invalid_hook_no_async.rs:6:63
+  |
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+  |                                                               ^^^^^^^^^^^^^^ `std::option::Option<AppsyncResponse>` is not a future
+  |
+  = help: the trait `Future` is not implemented for `std::option::Option<AppsyncResponse>`
+note: required by a bound in `call_hook`
+ --> tests/fail/invalid_hook_no_async.rs:6:63
+  |
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+  |                                                               ^^^^^^^^^^^^^^ required by this bound in `call_hook`

lambda-appsync-proc/tests/fail/invalid_hook_ret.rs

@@ -0,0 +1,9 @@
+mod no_run {
+    use lambda_appsync::{appsync_lambda_main, AppsyncEvent};
+    async fn verify_request(_event: &AppsyncEvent<Operation>) -> Option<String> {
+        None // Allow all requests
+    }
+    appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+}
+
+fn main() {}

lambda-appsync-proc/tests/fail/invalid_hook_ret.stderr

@@ -0,0 +1,13 @@
+error[E0271]: expected `impl Future<Output = Option<String>>` to be a future that resolves to `Option<AppsyncResponse>`, but it resolves to `Option<String>`
+ --> tests/fail/invalid_hook_ret.rs:6:63
+  |
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+  |                                                               ^^^^^^^^^^^^^^ expected `Option<AppsyncResponse>`, found `Option<String>`
+  |
+  = note: expected enum `std::option::Option<AppsyncResponse>`
+             found enum `std::option::Option<std::string::String>`
+note: required by a bound in `call_hook`
+ --> tests/fail/invalid_hook_ret.rs:6:63
+  |
+6 |     appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
+  |                                                               ^^^^^^^^^^^^^^ required by this bound in `call_hook`

lambda-appsync-proc/tests/pass/request_hook.rs

@@ -1,13 +1,9 @@
-use lambda_appsync::{appsync_lambda_main, AppsyncEvent, AppsyncResponse};
-
-async fn verify_request(_event: &AppsyncEvent<Operation>) -> Option<AppsyncResponse> {
-    None // Allow all requests
+mod no_run {
+    use lambda_appsync::{appsync_lambda_main, AppsyncEvent, AppsyncResponse};
+    async fn verify_request(_event: &AppsyncEvent<Operation>) -> Option<AppsyncResponse> {
+        None // Allow all requests
+    }
+    appsync_lambda_main!("../../../../schema.graphql", hook = verify_request);
 }
 
-appsync_lambda_main!(
-    "../../../../schema.graphql",
-    exclude_lambda_handler = true,
-    hook = verify_request
-);
-
 fn main() {}