Api metadata

packages/api/src/Base.ts

@@ -374,12 +374,21 @@ export default abstract class ApiBase<CodecResult, SubscriptionResult> implement
   }
 
   private async loadMeta (): Promise<boolean> {
+    const { metadata = {} } = this._options;
+
     // only load from on-chain if we are not a clone (default path), alternatively
     // just use the values from the source instance provided
     if (!this._options.source || !this._options.source._isReady) {
-      this._runtimeMetadata = await this._rpcBase.state.getMetadata();
-      this._runtimeVersion = await this._rpcBase.chain.getRuntimeVersion();
-      this._genesisHash = await this._rpcBase.chain.getBlockHash(0);
+      [this._genesisHash, this._runtimeVersion] = await Promise.all([
+        this._rpcBase.chain.getBlockHash(0),
+        this._rpcBase.chain.getRuntimeVersion()
+      ]);
+      const metadataKey = `${this._genesisHash}-${(this._runtimeVersion as RuntimeVersion).specVersion}`;
+      if (metadataKey in metadata) {
+        this._runtimeMetadata = new Metadata(metadata[metadataKey]);
+      } else {
+        this._runtimeMetadata = await this._rpcBase.state.getMetadata();
+      }
 
       // get unique types & validate
       this.runtimeMetadata.getUniqTypes(false);

packages/api/src/promise/Api.spec.ts

@@ -0,0 +1,52 @@
+// Copyright 2017-2019 @polkadot/api authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { ApiPromise } from '@polkadot/api';
+import { ApiOptions } from '@polkadot/api/types';
+import { Hash, Metadata } from '@polkadot/types';
+
+import Mock from '@polkadot/rpc-provider/mock/index';
+
+describe.skip('Metadata queries', () => {
+  let mock: Mock;
+
+  beforeEach(() => {
+    jest.setTimeout(3000000);
+    mock = new Mock();
+  });
+
+  it('Create API instance with metadata map and makes the runtime, rpc, state & extrinsics available', async () => {
+    const rpcData = await mock.send('state_getMetadata',[]);
+    const genesisHash = new Hash(await mock.send('chain_getBlockHash',[])).toHex();
+    const specVersion = 0;
+    const metadata: any = {};
+    const key = `${genesisHash}-${specVersion}`;
+    metadata[key] = rpcData;
+    const api = await ApiPromise.create({ provider: mock, metadata } as ApiOptions);
+
+    expect(api.genesisHash).toBeDefined();
+    expect(api.runtimeMetadata.toJSON()).toEqual(new Metadata(rpcData).toJSON());
+    expect(api.runtimeVersion).toBeDefined();
+    expect(api.rpc).toBeDefined();
+    expect(api.query).toBeDefined();
+    expect(api.tx).toBeDefined();
+    expect(api.derive).toBeDefined();
+  });
+
+  it('Create API instance without metadata and makes the runtime, rpc, state & extrinsics available', async () => {
+    const metadata = {};
+    const api = await ApiPromise.create({
+      provider: mock, metadata
+    });
+
+    expect(api.genesisHash).toBeDefined();
+    expect(api.runtimeMetadata).toBeDefined();
+    expect(api.runtimeVersion).toBeDefined();
+    expect(api.rpc).toBeDefined();
+    expect(api.query).toBeDefined();
+    expect(api.tx).toBeDefined();
+    expect(api.derive).toBeDefined();
+  });
+
+});

packages/api/src/types.ts

@@ -114,6 +114,13 @@ export interface ApiOptions {
    * @description Add custom derives to be injected
    */
   derives?: DeriveCustom;
+  /**
+   * @description prebundles is a map of 'genesis hash and runtime spec version' as key to metadata's hex string
+   * if genesis hash and runtime spec version matches, then use metadata, else fetch it from chain
+   */
+  metadata?: {
+    [key: string]: string
+  };
   /**
    * @description Transport Provider from rpc-provider. If not specified, it will default to
    * connecting to a WsProvider connecting localhost with the default port, i.e. `ws://127.0.0.1:9944`