preserve custom metadata when converting between Subxt metadata and frame_metadata (#1914)

Author: jsdw

metadata/src/from_into/v15.rs

@@ -284,9 +284,7 @@ mod into_v15 {
                     event_enum_ty: m.outer_enums.event_enum_ty.into(),
                     error_enum_ty: m.outer_enums.error_enum_ty.into(),
                 },
-                custom: v15::CustomMetadata {
-                    map: Default::default(),
-                },
+                custom: m.custom,
             }
         }
     }

testing/integration-tests/src/full_client/metadata/validation.rs

@@ -97,6 +97,25 @@ fn pallets_to_metadata(pallets: Vec<PalletMetadata>) -> Metadata {
     ))
 }
 
+#[subxt_test]
+async fn metadata_converting_works_ok() {
+    let ctx = test_context().await;
+    let api = ctx.client();
+
+    assert!(
+        node_runtime::is_codegen_valid_for(&api.metadata()),
+        "Should be valid initially"
+    );
+
+    let metadata = RuntimeMetadataV15::from((*api.metadata()).clone());
+    let metadata = v15_to_metadata(metadata);
+
+    assert!(
+        node_runtime::is_codegen_valid_for(&metadata),
+        "Should still be valid after conversion back and forth"
+    );
+}
+
 #[subxt_test]
 async fn full_metadata_check() {
     let ctx = test_context().await;