fix for when runtime API field name is _ (#1191)

* fix for when runtime API field name is _

* add a test

* formatting

---------

Co-authored-by: Tadeo hepperle <tadeo@do-mix.de>

codegen/src/api/runtime_apis.rs

@@ -36,8 +36,14 @@ fn generate_runtime_api(
             .then_some(quote! { #( #[doc = #docs ] )* })
             .unwrap_or_default();
 
-        let inputs: Vec<_> = method.inputs().map(|input| {
-            let name = format_ident!("{}", &input.name);
+        let inputs: Vec<_> = method.inputs().enumerate().map(|(idx, input)| {
+            // These are method names, which can just be '_', but struct field names can't
+            // just be an underscore, so fix any such names we find to work in structs.
+            let name = if input.name == "_" {
+                format_ident!("_{}", idx)
+            } else {
+                format_ident!("{}", &input.name)
+            };
             let ty = type_gen.resolve_type_path(input.ty);
 
             let param = quote!(#name: #ty);

testing/ui-tests/src/dispatch_errors.rs

@@ -11,13 +11,13 @@ use generate_custom_metadata::dispatch_error::{
 use frame_metadata::RuntimeMetadataPrefixed;
 
 pub fn metadata_array_dispatch_error() -> RuntimeMetadataPrefixed {
-    generate_metadata_from_pallets_custom_dispatch_error::<ArrayDispatchError>(vec![])
+    generate_metadata_from_pallets_custom_dispatch_error::<ArrayDispatchError>(vec![], vec![])
 }
 
 pub fn metadata_legacy_dispatch_error() -> RuntimeMetadataPrefixed {
-    generate_metadata_from_pallets_custom_dispatch_error::<LegacyDispatchError>(vec![])
+    generate_metadata_from_pallets_custom_dispatch_error::<LegacyDispatchError>(vec![], vec![])
 }
 
 pub fn metadata_named_field_dispatch_error() -> RuntimeMetadataPrefixed {
-    generate_metadata_from_pallets_custom_dispatch_error::<NamedFieldDispatchError>(vec![])
+    generate_metadata_from_pallets_custom_dispatch_error::<NamedFieldDispatchError>(vec![], vec![])
 }

testing/ui-tests/src/lib.rs

@@ -12,6 +12,7 @@
 //! to automatically regenerate `stderr` files, but don't forget to check that new files make sense.
 
 mod dispatch_errors;
+mod runtime_apis;
 mod storage;
 mod utils;
 
@@ -34,6 +35,13 @@ fn ui_tests() {
             .build(storage::metadata_storage_map_no_keys()),
     );
 
+    // Check runtime APIs with _ in method names work
+    t.pass(
+        m.new_test_case()
+            .name("runtime_api_underscore_method_name")
+            .build(runtime_apis::metadata_runtime_api_underscore_method_name()),
+    );
+
     // Test that the codegen can handle the different types of DispatchError.
     t.pass(
         m.new_test_case()

testing/ui-tests/src/runtime_apis.rs

@@ -0,0 +1,29 @@
+// Copyright 2019-2023 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use frame_metadata::{
+    v15::{RuntimeApiMetadata, RuntimeApiMethodMetadata, RuntimeApiMethodParamMetadata},
+    RuntimeMetadataPrefixed,
+};
+
+use crate::utils::generate_metadata_from_runtime_apis;
+
+/// Generate metadata which contains a `Map` storage entry with no hashers/values.
+/// This is a bit of an odd case, but it was raised in https://github.com/paritytech/subxt/issues/552,
+/// and this test will fail before the fix and should pass once the fix is applied.
+pub fn metadata_runtime_api_underscore_method_name() -> RuntimeMetadataPrefixed {
+    generate_metadata_from_runtime_apis(vec![RuntimeApiMetadata {
+        name: "MyApi".to_owned(),
+        docs: vec![],
+        methods: vec![RuntimeApiMethodMetadata {
+            name: "my_method".to_owned(),
+            inputs: vec![RuntimeApiMethodParamMetadata {
+                name: "_".to_owned(), // The important bit we're testing.
+                ty: 0.into(),         // we don't care what type this is.
+            }],
+            output: 0.into(), // we don't care what type this is.
+            docs: vec![],
+        }],
+    }])
+}

testing/ui-tests/src/utils/mod.rs

@@ -7,12 +7,12 @@ mod metadata_test_runner;
 use frame_metadata::{
     v15::{
         CustomMetadata, ExtrinsicMetadata, OuterEnums, PalletMetadata, PalletStorageMetadata,
-        RuntimeMetadataV15, StorageEntryMetadata,
+        RuntimeApiMetadata, RuntimeMetadataV15, StorageEntryMetadata,
     },
     RuntimeMetadataPrefixed,
 };
 use generate_custom_metadata::dispatch_error::ArrayDispatchError;
-use scale_info::{meta_type, IntoPortable, TypeInfo};
+use scale_info::{form::PortableForm, meta_type, IntoPortable, TypeInfo};
 
 pub use metadata_test_runner::MetadataTestRunner;
 
@@ -21,6 +21,7 @@ pub use metadata_test_runner::MetadataTestRunner;
 /// type matching the generic type param provided.
 pub fn generate_metadata_from_pallets_custom_dispatch_error<DispatchError: TypeInfo + 'static>(
     pallets: Vec<PalletMetadata>,
+    runtime_apis: Vec<RuntimeApiMetadata<PortableForm>>,
 ) -> RuntimeMetadataPrefixed {
     // We don't care about the extrinsic type.
     let extrinsic = ExtrinsicMetadata {