Fix Struct decoding for null (#4112)

* Fix Struct decoding for null

* CHANGELOG

* 6.5.2

packages/types/package.json

@@ -10,7 +10,6 @@
   "license": "Apache-2.0",
   "maintainers": [],
   "name": "@polkadot/types",
-  "private": false,
   "repository": {
     "directory": "packages/types",
     "type": "git",
@@ -21,7 +20,7 @@
     "./detectPackage.cjs"
   ],
   "type": "module",
-  "version": "6.5.2-3",
+  "version": "6.5.2",
   "main": "index.js",
   "dependencies": {
     "@babel/runtime": "^7.15.4",
@@ -31,8 +30,8 @@
   },
   "devDependencies": {
     "@polkadot/keyring": "^7.6.1",
-    "@polkadot/types-support": "6.5.2-3",
+    "@polkadot/types-support": "6.5.2",
     "@types/bn.js": "^4.11.6",
     "bn.js": "^4.12.0"
   }
-}
+}

packages/types/src/codec/Struct.spec.ts

@@ -52,15 +52,16 @@ describe('Struct', (): void => {
     testEncode('toString', '{"foo":"bazzing","bar":69}');
   });
 
-  it('decodes null', (): void => {
-    expect(
-      new (
-        Struct.with({
-          txt: Text,
-          u32: U32
-        })
-      )(registry, null).toString()
-    ).toEqual('{}');
+  it('decodes null/undefined/empty correctly (& equivalently)', (): void => {
+    const Clazz = Struct.with({
+      txt: Text,
+      u32: U32
+    });
+    const expected = { txt: '', u32: '0' };
+
+    expect(new Clazz(registry, {}).toHuman()).toEqual(expected);
+    expect(new Clazz(registry, null).toHuman()).toEqual(expected);
+    expect(new Clazz(registry, undefined).toHuman()).toEqual(expected);
   });
 
   it('decodes reusing instantiated inputs', (): void => {

packages/types/src/codec/Struct.ts

@@ -113,12 +113,10 @@ function decodeStruct <T> (registry: Registry, Types: ConstructorDef, value: unk
 
       return raw;
     }, {} as T);
-  } else if (!value) {
-    return {} as T;
   }
 
   // We assume from here that value is a JS object (Array, Map, Object)
-  return decodeStructFromObject(registry, Types, value, jsonMap);
+  return decodeStructFromObject(registry, Types, value || {}, jsonMap);
 }
 
 /**
@@ -147,7 +145,7 @@ export class Struct<
   readonly #Types: ConstructorDef;
 
   // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
-  constructor (registry: Registry, Types: S, value: V | Map<unknown, unknown> | unknown[] | string = {} as V, jsonMap: Map<keyof S, string> = new Map()) {
+  constructor (registry: Registry, Types: S, value?: V | Map<unknown, unknown> | unknown[] | string | null, jsonMap: Map<keyof S, string> = new Map()) {
     super(Object.entries(decodeStruct(registry, mapToTypeMap(registry, Types), value, jsonMap)));
 
     this.registry = registry;