Handle storage with optional modifiers (#717)

* Handle storage with optional modifiers

* Storage docs indicate Option

* Cleanup Option logic

* Convert Optional derive to use Option

* Bump version, update changelog

* Update CHANGELOG description

* Enum.spec.js -> Enum.spec.ts

* Add isEmpty to primitive types

CHANGELOG.md

@@ -1,3 +1,19 @@
+# 0.45.1
+
+- Storage with option values now correctly return `Option<Type>` and is indicated as such in the documentation
+
+```js
+// old
+const ll = await api.query.session.lastLengthChange();
+
+console.log('ll', ll /* BlockNumber */); // would be 0 if not set yet
+
+// new
+const llo = await api.query.session.lastLengthChange();
+
+console.log('llo', llo.unwrapOr('not set') /* Option<BlockNumber> */)
+```
+
 # 0.44.1
 
 - Split primitives and types into seperate folders. This should not affect external use since the exports remain the same, however does have an impact where classes are referenced directly. e.g.

lerna.json

@@ -9,5 +9,5 @@
   "packages": [
     "packages/*"
   ],
-  "version": "0.44.1"
+  "version": "0.45.0"
 }

packages/api-derive/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/api-derive",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Common functions used across Polkadot, derived from RPC calls and storage queries.",
   "main": "index.js",
   "keywords": [
@@ -31,8 +31,8 @@
   "homepage": "https://github.com/polkadot-js/api/tree/master/packages/api-derive#readme",
   "dependencies": {
     "@babel/runtime": "^7.3.1",
-    "@polkadot/api": "^0.44.1",
-    "@polkadot/types": "^0.44.1",
+    "@polkadot/api": "^0.45.0",
+    "@polkadot/types": "^0.45.0",
     "@types/memoizee": "^0.4.2",
     "memoizee": "^0.4.14"
   }

packages/api-derive/src/democracy/referendumInfo.ts

@@ -6,7 +6,7 @@ import BN from 'bn.js';
 import { Observable } from 'rxjs';
 import { map } from 'rxjs/operators';
 import { ApiInterface$Rx } from '@polkadot/api/types';
-import { ReferendumInfo, ReferendumIndex } from '@polkadot/types/index';
+import { Option, ReferendumInfo, ReferendumIndex } from '@polkadot/types/index';
 
 import { drr } from '../util/drr';
 
@@ -16,27 +16,32 @@ import { drr } from '../util/drr';
  * A [[ReferendumInfo]] with an additional `index` field
  */
 export class ReferendumInfoExtended extends ReferendumInfo {
-  private _index: ReferendumIndex;
-
-  constructor (info: ReferendumInfo, index: BN | number) {
+  constructor (info: any) {
     super(info);
 
-    this._index = new ReferendumIndex(index);
+    this.set('index', new ReferendumIndex(info.index));
   }
 
   /**
    * @description Convenience getter, returns the referendumIndex
    */
   get index (): ReferendumIndex {
-    return this._index;
+    return this.get('index') as ReferendumIndex;
   }
 }
 
 export function referendumInfo (api: ApiInterface$Rx) {
-  return (id: BN | number): Observable<ReferendumInfoExtended> => {
-    return (api.query.democracy.referendumInfoOf(id) as Observable<ReferendumInfo>)
+  return (index: BN | number): Observable<Option<ReferendumInfoExtended>> => {
+    return (api.query.democracy.referendumInfoOf(index) as Observable<Option<ReferendumInfo>>)
       .pipe(
-        map((info) => new ReferendumInfoExtended(info, id)),
+        map((info) =>
+          new Option<ReferendumInfoExtended>(
+            ReferendumInfoExtended,
+            info.isSome
+              ? { ...info.toJSON(), index }
+              : null
+          )
+        ),
         drr()
       );
   };

packages/api-derive/src/democracy/referendumInfos.ts

@@ -5,6 +5,7 @@
 import BN from 'bn.js';
 import { combineLatest, Observable, of } from 'rxjs';
 import { ApiInterface$Rx } from '@polkadot/api/types';
+import { Option } from '@polkadot/types/index';
 
 import { drr } from '../util/drr';
 import { referendumInfo, ReferendumInfoExtended } from './referendumInfo';
@@ -12,7 +13,7 @@ import { referendumInfo, ReferendumInfoExtended } from './referendumInfo';
 export function referendumInfos (api: ApiInterface$Rx) {
   const referendumInfoOf = referendumInfo(api);
 
-  return (ids: Array<BN | number> = []): Observable<Array<ReferendumInfoExtended>> => {
+  return (ids: Array<BN | number> = []): Observable<Array<Option<ReferendumInfoExtended>>> => {
     return !ids || !ids.length
       ? of([]).pipe(drr())
       : combineLatest(

packages/api-derive/src/democracy/referendums.ts

@@ -5,14 +5,14 @@
 import { combineLatest, Observable, of } from 'rxjs';
 import { switchMap } from 'rxjs/operators';
 import { ApiInterface$Rx } from '@polkadot/api/types';
-import { ReferendumIndex } from '@polkadot/types/index';
+import { Option, ReferendumIndex } from '@polkadot/types/index';
 
 import { drr } from '../util/drr';
 import { ReferendumInfoExtended } from './referendumInfo';
 import { referendumInfos } from './referendumInfos';
 
 export function referendums (api: ApiInterface$Rx) {
-  return (): Observable<Array<ReferendumInfoExtended>> =>
+  return (): Observable<Array<Option<ReferendumInfoExtended>>> =>
     (combineLatest(
       api.query.democracy.nextTally(),
       api.query.democracy.referendumCount()

packages/api-derive/src/session/sessionProgress.ts

@@ -6,7 +6,7 @@ import BN from 'bn.js';
 import { combineLatest, Observable } from 'rxjs';
 import { map } from 'rxjs/operators';
 import { ApiInterface$Rx } from '@polkadot/api/types';
-import { BlockNumber } from '@polkadot/types/index';
+import { BlockNumber, Option } from '@polkadot/types/index';
 
 import { bestNumber } from '../chain';
 import { drr } from '../util/drr';
@@ -21,7 +21,7 @@ export function sessionProgress (api: ApiInterface$Rx) {
       map(
         ([bestNumber, sessionLength, lastLengthChange]) =>
           (bestNumber || new BN(0))
-            .sub(lastLengthChange as BlockNumber || new BN(0))
+            .sub((lastLengthChange as Option<BlockNumber>).unwrapOr(new BN(0)))
             .add(sessionLength as BlockNumber || new BN(1))
             .mod(sessionLength as BlockNumber || new BN(1))
       ),

packages/api/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/api",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Promise and RxJS wrappers around the Polkadot JS RPC",
   "main": "index.js",
   "keywords": [
@@ -30,12 +30,12 @@
   "homepage": "https://github.com/polkadot-js/api/tree/master/packages/api#readme",
   "dependencies": {
     "@babel/runtime": "^7.3.1",
-    "@polkadot/api-derive": "^0.44.1",
-    "@polkadot/extrinsics": "^0.44.1",
-    "@polkadot/rpc-provider": "^0.44.1",
-    "@polkadot/rpc-rx": "^0.44.1",
-    "@polkadot/storage": "^0.44.1",
-    "@polkadot/types": "^0.44.1",
+    "@polkadot/api-derive": "^0.45.0",
+    "@polkadot/extrinsics": "^0.45.0",
+    "@polkadot/rpc-provider": "^0.45.0",
+    "@polkadot/rpc-rx": "^0.45.0",
+    "@polkadot/storage": "^0.45.0",
+    "@polkadot/types": "^0.45.0",
     "@polkadot/util-crypto": "^0.34.20"
   }
 }

packages/rpc-core/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/rpc-core",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "A JavaScript wrapper for the Polkadot JsonRPC interface",
   "main": "index.js",
   "keywords": [
@@ -30,9 +30,9 @@
   "homepage": "https://github.com/polkadot-js/api/tree/master/packages/rpc-core#readme",
   "dependencies": {
     "@babel/runtime": "^7.3.1",
-    "@polkadot/jsonrpc": "^0.44.1",
-    "@polkadot/rpc-provider": "^0.44.1",
-    "@polkadot/types": "^0.44.1",
+    "@polkadot/jsonrpc": "^0.45.0",
+    "@polkadot/rpc-provider": "^0.45.0",
+    "@polkadot/types": "^0.45.0",
     "@polkadot/util": "^0.34.20"
   }
 }

packages/rpc-core/src/formatting.spec.ts

@@ -2,6 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
+import BN from 'bn.js';
 import storage from '@polkadot/storage/static';
 
 import Api from './index';
@@ -13,8 +14,8 @@ const ENC_ONE = '0x24988a82b3bbaae58680bc9de5dea5aa';
 const ENC_TWO = '0xdb190750267d8849c35316ec9d342111';
 
 describe('formatting', () => {
-  let api;
-  let provider;
+  let api: Api;
+  let provider: any;
 
   beforeEach(() => {
     provider = {
@@ -51,30 +52,29 @@ describe('formatting', () => {
   });
 
   it('encodes multiple keys, decoding multiple results', (done) => {
-    api.state
-      .subscribeStorage(
-        [
-          [storage.balances.freeBalance, ADDR_ONE],
-          [storage.balances.freeBalance, ADDR_TWO]
-        ],
-        (value) => {
-          console.error(value);
+    return api.state.subscribeStorage(
+      [
+        [storage.balances.freeBalance, ADDR_ONE],
+        [storage.balances.freeBalance, ADDR_TWO]
+      ],
+      (value: any) => {
+        console.error(value);
 
-          expect(
-            provider.subscribe
-          ).toHaveBeenCalledWith(
-            'state_storage',
-            'state_subscribeStorage',
-            [[ENC_ONE, ENC_TWO]],
-            expect.anything()
-          );
-          expect(
-            value.map((balance) =>
-              balance.toNumber()
-            )
-          ).toEqual([513, 258]);
+        expect(
+          provider.subscribe
+        ).toHaveBeenCalledWith(
+          'state_storage',
+          'state_subscribeStorage',
+          [[ENC_ONE, ENC_TWO]],
+          expect.anything()
+        );
+        expect(
+          value.map((balance: BN) =>
+            balance.toNumber()
+          )
+        ).toEqual([513, 258]);
 
-          done();
-        });
+        done();
+      });
   });
 });

packages/rpc-core/src/index.spec.ts

@@ -5,13 +5,13 @@
 import Api from './index';
 
 describe('Api', () => {
-  let api;
-  let provider;
-  let sendSpy;
+  let api: Api;
+  let provider: any;
+  let sendSpy: any;
 
   beforeEach(() => {
     provider = {
-      send: (method, params) => {
+      send: (method: any, params: Array<any>) => {
         return Promise.resolve(params[0]);
       }
     };
@@ -25,7 +25,7 @@ describe('Api', () => {
 
   it('requires a provider with a send method', () => {
     expect(
-      () => new Api({})
+      () => new Api({} as any)
     ).toThrow(/Expected Provider/);
   });
 

packages/rpc-core/src/index.ts

@@ -9,8 +9,8 @@ import { RpcInterface, RpcInterface$Method, RpcInterface$Section } from './types
 import interfaces from '@polkadot/jsonrpc/index';
 import WsProvider from '@polkadot/rpc-provider/ws';
 import { Codec } from '@polkadot/types/types';
-import { StorageChangeSet, StorageKey, Vector, createType } from '@polkadot/types/index';
-import { ExtError, assert, isFunction, logger } from '@polkadot/util';
+import { Option, StorageChangeSet, StorageKey, Vector, createClass, createType } from '@polkadot/types/index';
+import { ExtError, assert, isFunction, isNull, logger } from '@polkadot/util';
 
 const l = logger('rpc-core');
 
@@ -189,24 +189,32 @@ export default class Rpc implements RpcInterface {
     if (method.type === 'StorageData') {
       // single return value (via state.getStorage), decode the value based on the
       // outputType that we have specified. Fallback to Data on nothing
-      const type = (params[0] as StorageKey).outputType || 'Data';
+      const key = params[0] as StorageKey;
+      const type = key.outputType || 'Data';
+      const meta = key.meta || { default: undefined, modifier: { isOptional: true } };
+      const value = isNull(result)
+        ? null
+        : base;
 
-      return createType(type, base);
+      return meta.modifier.isOptional
+        ? new Option(createClass(type), value)
+        : createType(type, value);
     } else if (method.type === 'StorageChangeSet') {
       // multiple return values (via state.storage subscription), decode the values
       // one at a time, all based on the query types. Three values can be returned -
       //   - Base - There is a valid value, non-empty
       //   - null - The storage key is empty (but in the resultset)
       //   - undefined - The storage value is not in the resultset
-      return (params[0] as Vector<StorageKey>).reduce((result, _key: StorageKey) => {
+      return (params[0] as Vector<StorageKey>).reduce((result, key: StorageKey) => {
         // Fallback to Data (i.e. just the encoding) if we don't have a specific type
-        const type = _key.outputType || 'Data';
+        const type = key.outputType || 'Data';
 
         // see if we have a result value for this specific key
-        const key = _key.toHex();
+        const hexKey = key.toHex();
         const item = (base as StorageChangeSet).changes.find((item) =>
-          item.key.toHex() === key
+          item.key.toHex() === hexKey
         );
+        const meta = key.meta || { default: undefined, modifier: { isOptional: true } };
 
         // if we don't have a value, do not fill in the entry, it will be up to the
         // caller to sort this out, either ignoring or having a cache for older values
@@ -214,11 +222,13 @@ export default class Rpc implements RpcInterface {
           !item
             ? undefined
             : (
-              // for `null` we fallback to the default value, or create an empty type,
-              // otherwise we return the actual value as retrieved
-              item.value.isNone
-                ? createType(type, (_key.meta || { default: undefined }).default)
-                : createType(type, item.value.unwrap())
+              meta.modifier.isOptional
+                // create option either with the existing value, or empty when
+                // there is no value returned
+                ? new Option(createClass(type), item.value.unwrapOr(null))
+                // for `null` we fallback to the default value, or create an empty type,
+                // otherwise we return the actual value as retrieved
+                : createType(type, item.value.unwrapOr(meta.default))
             )
         );
 

packages/rpc-core/src/methodSend.spec.ts

@@ -5,9 +5,9 @@
 import Api from './index';
 
 describe('methodSend', () => {
-  let api;
-  let methods;
-  let provider;
+  let api: Api;
+  let methods: any;
+  let provider: any;
 
   beforeEach(() => {
     methods = {
@@ -37,6 +37,7 @@ describe('methodSend', () => {
   });
 
   it('wraps errors with the call signature', () => {
+    // @ts-ignore private method
     const method = api.createMethodSend(methods.blah);
 
     return method().catch((error) => {
@@ -45,6 +46,7 @@ describe('methodSend', () => {
   });
 
   it('checks for mismatched parameters', () => {
+    // @ts-ignore private method
     const method = api.createMethodSend(methods.bleh);
 
     return method(1).catch((error) => {
@@ -53,6 +55,7 @@ describe('methodSend', () => {
   });
 
   it('calls the provider with the correct parameters', () => {
+    // @ts-ignore private method
     const method = api.createMethodSend(methods.blah);
 
     // Args are length-prefixed, because it's a Bytes

packages/rpc-provider/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/rpc-provider",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Transport providers for the API",
   "main": "index.js",
   "keywords": [
@@ -31,7 +31,7 @@
   "dependencies": {
     "@babel/runtime": "^7.3.1",
     "@polkadot/keyring": "^0.34.20",
-    "@polkadot/storage": "^0.44.1",
+    "@polkadot/storage": "^0.45.0",
     "@polkadot/util": "^0.34.20",
     "@polkadot/util-crypto": "^0.34.20",
     "@types/nock": "^9.3.1",

packages/rpc-rx/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/rpc-rx",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "An RxJs wrapper around the Polkadot JS API",
   "main": "index.js",
   "keywords": [
@@ -30,8 +30,8 @@
   "homepage": "https://github.com/polkadot-js/api/tree/master/packages/rpc-rx#readme",
   "dependencies": {
     "@babel/runtime": "^7.3.1",
-    "@polkadot/rpc-core": "^0.44.1",
-    "@polkadot/rpc-provider": "^0.44.1",
+    "@polkadot/rpc-core": "^0.45.0",
+    "@polkadot/rpc-provider": "^0.45.0",
     "@types/memoizee": "^0.4.2",
     "@types/rx": "^4.1.1",
     "memoizee": "^0.4.14",

packages/type-extrinsics/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/extrinsics",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "main": "index.js",
   "repository": "https://github.com/polkadot-js/api.git",
   "author": "Jaco Greeff <jacogr@gmail.com>",
@@ -11,7 +11,7 @@
   "license": "Apache-2.0",
   "dependencies": {
     "@babel/runtime": "^7.3.1",
-    "@polkadot/types": "^0.44.1",
+    "@polkadot/types": "^0.45.0",
     "@polkadot/util": "^0.34.20"
   }
 }

packages/type-jsonrpc/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/jsonrpc",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Method definitions for the Polkadot RPC layer",
   "main": "index.js",
   "engines": {

packages/type-storage/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/storage",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Generic wrapper wrapper around state storage",
   "main": "index.js",
   "engines": {
@@ -31,7 +31,7 @@
   "dependencies": {
     "@babel/runtime": "^7.3.1",
     "@polkadot/keyring": "^0.34.20",
-    "@polkadot/types": "^0.44.1",
+    "@polkadot/types": "^0.45.0",
     "@polkadot/util": "^0.34.20",
     "@polkadot/util-crypto": "^0.34.20"
   }

packages/type-storage/src/substrate.ts

@@ -20,7 +20,7 @@ const createRuntimeFunction = (method: string, key: string, { documentation, typ
     new Text(method),
     {
       documentation: new Vector(Text, [documentation]),
-      modifier: new StorageFunctionModifier(0),
+      modifier: new StorageFunctionModifier(1), // default
       type: new StorageFunctionType(type, 0),
       toJSON: (): any =>
         key

packages/types/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/types",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Implementation of the Parity codec",
   "main": "index.js",
   "keywords": [

packages/types/src/Metadata/v0/Modules.ts

@@ -124,7 +124,14 @@ export class ModuleMetadata extends Struct {
 
 export class StorageFunctionModifier extends Enum {
   constructor (value?: any) {
-    super(['None', 'Default', 'Required'], value);
+    super(['Optional', 'Default', 'Required'], value);
+  }
+
+  /**
+   * @description `true` if the storage entry is optional
+   */
+  get isOptional (): boolean {
+    return this.toNumber() === 0;
   }
 }
 

packages/types/src/Metadata/v1/toV0.ts

@@ -16,10 +16,10 @@ function storageV0 (mod: MetadataModuleV1): StorageMetadata | null {
 
   return new StorageMetadata({
     prefix: mod.prefix,
-    functions: mod.storage.unwrap().map(({ docs, fallback, name, type }) =>
+    functions: mod.storage.unwrap().map(({ docs, fallback, modifier, name, type }) =>
       new StorageFunctionMetadata({
         name,
-        modifier: 0, // unused, don't specify
+        modifier: modifier.toNumber(),
         type,
         default: fallback,
         documentation: docs

packages/types/src/codec/AbstractInt.ts

@@ -65,6 +65,13 @@ export default abstract class AbstractInt extends BN implements Codec {
     return this._bitLength / 8;
   }
 
+  /**
+   * @description Checks if the value is a zero value (align elsewhere)
+   */
+  get isEmpty (): boolean {
+    return this.isZero();
+  }
+
   /**
    * @description Returns the number of bits in the value
    */

packages/types/src/codec/Compact.ts

@@ -73,6 +73,13 @@ export default class Compact extends Base<UInt | Moment> implements Codec {
     return this.toU8a().length;
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.raw.isEmpty;
+  }
+
   /**
    * @description Returns the number of bits in the value
    */

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

@@ -4,15 +4,16 @@
 
 import Enum from './Enum';
 
-const testDecode = (type, input, expected) =>
+const testDecode = (type: string, input: any, expected: any) =>
   it(`can decode from ${type}`, () => {
     const e = new Enum(['foo', 'bar'], input);
     expect(e.toString()).toBe(expected);
   });
 
-const testEncode = (to, expected) =>
+const testEncode = (to: 'toJSON' | 'toNumber' | 'toString' | 'toU8a', expected: any) =>
   it(`can encode ${to}`, () => {
     const e = new Enum(['foo', 'bar'], 1);
+
     expect(e[to]()).toEqual(expected);
   });
 

packages/types/src/codec/Enum.ts

@@ -65,6 +65,13 @@ export default class Enum extends Base<number> implements Codec {
     return 1;
   }
 
+  /**
+   * @description Checks if the value is an empty value (always false)
+   */
+  get isEmpty (): boolean {
+    return false;
+  }
+
   /**
    * @description Compares the value of the input to see if there is a match
    */

packages/types/src/codec/EnumType.ts

@@ -122,6 +122,13 @@ export default class EnumType<T> extends Base<Codec> implements Codec {
     return this._index;
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.isEmpty;
+  }
+
   /**
    * @description Checks if the Enum points to a [[Null]] type
    */

packages/types/src/codec/Option.ts

@@ -53,6 +53,13 @@ export default class Option<T extends Codec> extends Base<T> implements Codec {
     return 1 + this.raw.encodedLength;
   }
 
+  /**
+   * @description Checks if the Option has no value
+   */
+  get isEmpty (): boolean {
+    return this.isNone;
+  }
+
   /**
    * @description Checks if the Option has no value
    */

packages/types/src/codec/Struct.ts

@@ -139,6 +139,21 @@ export default class Struct<
     };
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    const items = this.toArray();
+
+    for (let i = 0; i < items.length; i++) {
+      if (!items[i].isEmpty) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
   /**
    * @description Returns the Type description to sthe structure
    */

packages/types/src/codec/Tuple.ts

@@ -62,6 +62,13 @@ export default class Tuple extends Array<Codec> implements Codec {
     }, 0);
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.length === 0;
+  }
+
   /**
    * @description The types definition of the tuple
    */

packages/types/src/codec/Vector.ts

@@ -53,6 +53,16 @@ export default class Vector<
     };
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.length === 0;
+  }
+
+  /**
+   * @description The type for the items
+   */
   get Type (): string {
     return this._Type.name;
   }

packages/types/src/codec/index.ts

@@ -22,5 +22,5 @@ export { default as U8a } from './U8a';
 export { default as UInt } from './UInt';
 
 // Type management helper functions
-export { default as createType, getTypeClass, getTypeDef, TypeDef, TypeDefInfo } from './createType';
+export { default as createType, createClass, getTypeClass, getTypeDef, TypeDef, TypeDefInfo } from './createType';
 export { default as typeRegistry } from './typeRegistry';

packages/types/src/primitive/Bool.ts

@@ -36,6 +36,13 @@ export default class Bool extends Boolean implements Codec {
     return 1;
   }
 
+  /**
+   * @description Checks if the value is an empty value (always false)
+   */
+  get isEmpty (): boolean {
+    return false;
+  }
+
   /**
    * @description Compares the value of the input to see if there is a match
    */

packages/types/src/primitive/Moment.ts

@@ -52,6 +52,13 @@ export default class Moment extends Date implements Codec {
     return BITLENGTH / 8;
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.getTime() === 0;
+  }
+
   /**
    * @description Compares the value of the input to see if there is a match
    */

packages/types/src/primitive/Null.ts

@@ -18,6 +18,13 @@ export default class Null implements Codec {
     return 0;
   }
 
+  /**
+   * @description Checks if the value is an empty value (always true)
+   */
+  get isEmpty (): boolean {
+    return true;
+  }
+
   /**
    * @description Compares the value of the input to see if there is a match
    */

packages/types/src/primitive/Text.ts

@@ -46,6 +46,13 @@ export default class Text extends String implements Codec {
     return this.toU8a().length;
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.length === 0;
+  }
+
   /**
    * @description The length of the value
    */

packages/types/src/scripts/MetadataMd.ts

@@ -145,7 +145,10 @@ function addStorage (metadata: MetadataV0) {
       const methodName = stringLowerFirst(func.name.toString());
       const arg = func.type.isMap ? ('`' + func.type.asMap.key.toString() + '`') : '';
       const doc = func.documentation.reduce((md, doc) => `${md} ${doc}`, '');
-      const renderSignature = `${md}\n▸ **${methodName}**(${arg}): ` + '`' + func.type + '`';
+      const type = func.modifier.isOptional
+        ? `Option<${func.type}>`
+        : func.type;
+      const renderSignature = `${md}\n▸ **${methodName}**(${arg}): ` + '`' + type + '`';
       const renderSummary = `${doc ? `\n- **summary**: ${doc}\n` : '\n'}`;
 
       return renderSignature + renderSummary;

packages/types/src/type/Address.ts

@@ -6,6 +6,7 @@ import BN from 'bn.js';
 import { decodeAddress } from '@polkadot/keyring';
 import { hexToU8a, isBn, isHex, isNumber, isU8a, u8aConcat, u8aToHex, u8aToU8a, u8aToBn } from '@polkadot/util';
 
+import { Codec } from '../types';
 import Base from '../codec/Base';
 import AccountId from './AccountId';
 import AccountIndex from './AccountIndex';
@@ -22,7 +23,7 @@ export const ACCOUNT_ID_PREFIX = new Uint8Array([0xff]);
  * we extend from Base with an AccountId/AccountIndex wrapper. Basically the Address
  * is encoded as `[ <prefix-byte>, ...publicKey/...bytes ]` as per spec
  */
-export default class Address extends Base<AccountId | AccountIndex> {
+export default class Address extends Base<AccountId | AccountIndex> implements Codec {
   constructor (value: AnyAddress = new Uint8Array()) {
     super(
       Address.decodeAddress(value)
@@ -75,6 +76,13 @@ export default class Address extends Base<AccountId | AccountIndex> {
     );
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return this.raw.isEmpty;
+  }
+
   /**
    * @description The length of the raw value, either AccountIndex or AccountId
    */

packages/types/src/type/ChainProperties.ts

@@ -30,6 +30,13 @@ export default class ChainProperties extends Map<string, any> implements Codec {
     return 0;
   }
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  get isEmpty (): boolean {
+    return [...this.keys()].length === 0;
+  }
+
   /**
    * @description The token decimals, if defined (de-facto standard only)
    */

packages/types/src/types.ts

@@ -33,6 +33,11 @@ export interface Codec {
    */
   encodedLength: number;
 
+  /**
+   * @description Checks if the value is an empty value
+   */
+  isEmpty: boolean;
+
   /**
    * @description Compares the value of the input to see if there is a match
    */
@@ -62,7 +67,9 @@ export interface Codec {
 
 export type CodecTo = 'toHex' | 'toJSON' | 'toString' | 'toU8a';
 
-export type Constructor<T = Codec> = { new(value?: any): T };
+export interface Constructor<T = Codec> {
+  new(...value: Array<any>): T;
+}
 
 export type ConstructorDef<T = Codec> = { [index: string]: Constructor<T> };