Bytes from StorageData (possibly prefixed) (#413)

* Bytes from StorageData (possibly prefixed)

* StorageData extends Data

* Cyclic-dep require, StorageData extends Bytes

packages/types/src/Bytes.spec.ts

@@ -3,15 +3,32 @@
 // of the Apache-2.0 license. See the LICENSE file for details.
 
 import Bytes from './Bytes';
+import StorageData from './StorageData';
 
 describe('Bytes', () => {
-  describe('hex decoding', () => {
-    const CODE = new Uint8Array([0x14, 0x3a, 0x63, 0x6f, 0x64, 0x65]);
+  const CODE = new Uint8Array([0x14, 0x3a, 0x63, 0x6f, 0x64, 0x65]);
 
+  describe('construction', () => {
     it('decodes when hex is not length prefixed', () => {
       expect(
         new Bytes('0x3a636f6465').toU8a()
       ).toEqual(CODE);
     });
+
+    it('creates via storagedata (no prefix)', () => {
+      expect(
+        new Bytes(
+          new StorageData('0x3a636f6465')
+        ).toU8a()
+      ).toEqual(CODE);
+    });
+
+    it('creates via storagedata (with length prefix)', () => {
+      expect(
+        new Bytes(
+          new StorageData('0x143a636f6465')
+        ).toU8a()
+      ).toEqual(CODE);
+    });
   });
 });

packages/types/src/Bytes.ts

@@ -17,6 +17,11 @@ export default class Bytes extends U8a {
   }
 
   private static decodeBytes (value: AnyU8a): Uint8Array {
+    // FIXME Cyclic dependency, however needed for the StoreageData check below. In a perfect
+    // world, we should probably be checking Bytes - however as a first step, check against
+    // StorageData to cater for the _specific_ problematic case
+    const StorageData = require('./StorageData').default;
+
     if (isHex(value)) {
       // FIXME We manually add the length prefix for hex for now
       // https://github.com/paritytech/substrate/issues/889
@@ -25,8 +30,17 @@ export default class Bytes extends U8a {
       return Bytes.decodeBytes(
         Compact.addLengthPrefix(u8a)
       );
+    } else if (value instanceof StorageData) {
+      // Here we cater for the actual StorageData that _could_ have a length prefix. In the
+      // case of `:code` it is not added, for others it is
+      const u8a = value as Uint8Array;
+      const [offset, length] = Compact.decodeU8a(u8a);
+
+      return u8a.length === length.addn(offset).toNumber()
+        ? u8a.subarray(offset)
+        : u8a;
     } else if (value instanceof U8a) {
-      // This is required. In the case of a U8a we already have gottent rid of the length,
+      // This is required. In the case of a U8a we already have gotten rid of the length,
       // i.e. new Bytes(new Bytes(...)) will work as expected
       return value;
     } else if (isU8a(value)) {

packages/types/src/StorageData.ts

@@ -4,5 +4,6 @@
 
 import Bytes from './Bytes';
 
+// Data retrieve via Storage queries and data for KeyValue pairs
 export default class StorageData extends Bytes {
 }