AccountId toString() with isEmpty (#592)

* AccountId toString() with isEmpty

* isEmpty is real isEmpty check

packages/types/src/AccountId.spec.ts

@@ -43,9 +43,9 @@ describe('AccountId', () => {
   });
 
   describe('encoding', () => {
-    const testEncode = (to: 'toHex' | 'toJSON' | 'toString' | 'toU8a', expected: Uint8Array | string) =>
+    const testEncode = (to: 'toHex' | 'toJSON' | 'toString' | 'toU8a', expected: Uint8Array | string, input: string = '5C62W7ELLAAfix9LYrcx5smtcffbhvThkM5x7xfMeYXCt72s') =>
       it(`can encode ${to}`, () => {
-        const a = new AccountId('5C62W7ELLAAfix9LYrcx5smtcffbhvThkM5x7xfMeYXCt72s');
+        const a = new AccountId(input);
 
         expect(a[to]()).toEqual(expected);
       });
@@ -53,6 +53,7 @@ describe('AccountId', () => {
     testEncode('toHex', '0x0102030405060708010203040506070801020304050607080102030405060708');
     testEncode('toJSON', '5C62W7ELLAAfix9LYrcx5smtcffbhvThkM5x7xfMeYXCt72s');
     testEncode('toString', '5C62W7ELLAAfix9LYrcx5smtcffbhvThkM5x7xfMeYXCt72s');
+    testEncode('toString', '-', '0x00');
     testEncode('toU8a', Uint8Array.from([
       1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8,
       1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8

packages/types/src/AccountId.ts

@@ -41,9 +41,16 @@ export default class AccountId extends U8aFixed {
   }
 
   /**
-   * @description Returns true if the type wraps a non-encodable value
+   * @description Returns true if the type wraps an empty value
    */
   get isEmpty (): boolean {
+    return this.length === 1 && this[0] === 0;
+  }
+
+  /**
+   * @description Returns true if the type wraps a non-valid value
+   */
+  get isInvalid (): boolean {
     return this.length !== 32;
   }
 
@@ -58,6 +65,8 @@ export default class AccountId extends U8aFixed {
    * @description Returns the string representation of the value
    */
   toString (): string {
-    return AccountId.encode(this);
+    return this.isEmpty
+      ? '-'
+      : AccountId.encode(this);
   }
 }