Sameness check for v12 indexes (#2609)

* Sameness check for indexes

* Update with older support

packages/metadata/src/Decorated/extrinsics/fromMetadata/index.ts

@@ -11,12 +11,15 @@ import createUnchecked from './createUnchecked';
 
 /** @internal */
 export default function fromMetadata (registry: Registry, metadata: RegistryMetadata): ModulesWithCalls {
-  return metadata.asLatest.modules
+  const modules = metadata.asLatest.modules;
+  const isIndexed = modules.some(({ index }) => !index.eqn(255));
+
+  return modules
     .filter(({ calls }) => calls.isSome)
     .reduce((result, { calls, index, name }: RegistryMetadataModule, _sectionIndex): ModulesWithCalls => {
-      const sectionIndex = index.eqn(255)
-        ? _sectionIndex
-        : index.toNumber();
+      const sectionIndex = isIndexed
+        ? index.toNumber()
+        : _sectionIndex;
       const section = stringCamelCase(name.toString());
 
       result[section] = calls.unwrap().reduce((newModule: Calls, callMetadata, methodIndex): Calls => {

packages/metadata/src/Metadata/v12/toLatest.ts

@@ -7,7 +7,7 @@ import { Registry, OverrideModuleType } from '@polkadot/types/types';
 
 import { getModuleTypes } from '@polkadot/types-known';
 import { Type } from '@polkadot/types/primitive';
-import { assert, stringCamelCase } from '@polkadot/util';
+import { stringCamelCase } from '@polkadot/util';
 
 // TODO Handle consts as well
 
@@ -88,11 +88,6 @@ function convertStorage (registry: Registry, { items, prefix }: StorageMetadataV
  * @internal
  **/
 export default function toLatest (registry: Registry, { extrinsic, modules }: MetadataV12): MetadataLatest {
-  const allIndexes = modules.map(({ index }) => index.toNumber());
-  const hasReserved = allIndexes.some((index) => index !== 255) && allIndexes.some((index) => index === 255);
-
-  assert(!hasReserved, 'This API implementation only supports module indexes 0-254, index 255 is marked as reserved');
-
   return registry.createType('MetadataLatest', {
     extrinsic,
     modules: modules.map((mod): ModuleMetadataLatest => {