🧼 Configure fallthrough contracts example

src/classes/Contract.ts

@@ -4,9 +4,7 @@ import {
   decodeRPCResponse,
   encodeData,
 } from './utils/encode-decode-transaction';
-import { buildRPCPostBody, post } from './utils/fetchers';
 /**
- *
  * @param txnData
  * @example
  */
@@ -71,19 +69,16 @@ export class BaseContract {
                   ? estimateGas(data)
                   : null;
               const req = async (): Promise<string> => {
-                return await post(
-                  this._provider.selectRpcUrl(),
-                  buildRPCPostBody('eth_call', [
-                    {
-                      to: this._address.toLowerCase(),
-                      data,
-                      // sometimes gas is defined in the ABI
-                      ...(decimalGas
-                        ? { gas: `0x${decimalGas.toString(16)}` }
-                        : {}),
-                    },
-                    'latest',
-                  ]),
+                return await this._provider.call(
+                  {
+                    to: this._address.toLowerCase(),
+                    data,
+                    // sometimes gas is defined in the ABI
+                    ...(decimalGas
+                      ? { gas: `0x${decimalGas.toString(16)}` }
+                      : {}),
+                  },
+                  'latest',
                 );
               };
               const nodeResponse = await req();
@@ -98,10 +93,7 @@ export class BaseContract {
 /**
  * Applies the unique contract's methods to the instantiated Contract in the constructor based-upon the provided ABI
  *
- * @param object
- * @param name
- * @param value
- * @example
+ * @internal
  */
 export function defineReadOnly<T>(object: T, name: string, value: any): void {
   Object.defineProperty(object, name, {
@@ -121,6 +113,8 @@ export function defineReadOnly<T>(object: T, name: string, value: any): void {
  * // UNI airdrop contract
  * const contractAddress = '0x090D4613473dEE047c3f2706764f49E0821D256e';
  * const provider = new JsonRpcProvider();
+ * // for more robust contract calls, provide a fallback:
+ * // const provider = new FallthroughProvider(['bad', 'https://free-eth-node.com/api/eth']);
  *
  * const JSONABI = [
  *   {

src/classes/test/Contract/ens.test.ts

@@ -1,6 +1,6 @@
 import { Contract as EthersContract } from '@ethersproject/contracts';
 import { StaticJsonRpcProvider } from '@ethersproject/providers';
-import { JsonRpcProvider } from '../../../index';
+import { FallthroughProvider } from '../../../index';
 import { Contract as EssentialEthContract } from '../../Contract';
 import { rpcUrls } from './../../../providers/test/rpc-urls';
 import { ensABI } from './ens-abi';
@@ -10,7 +10,11 @@ const JSONABI = ensABI;
 
 const rpcURL = rpcUrls.mainnet;
 const ethersProvider = new StaticJsonRpcProvider(rpcURL);
-const essentialEthProvider = new JsonRpcProvider(rpcURL);
+const essentialEthProvider = new FallthroughProvider([
+  'nope',
+  'https://flash-the-slow-api.herokuapp.com/delay/1',
+  rpcURL,
+]);
 
 const contractAddress = '0x57f1887a8BF19b14fC0dF6Fd9B2acc9Af147eA85';
 

src/classes/utils/fetchers.ts

@@ -2,8 +2,9 @@ import unfetch from 'isomorphic-unfetch';
 /**
  * Makes a post request with the specified JSON data, normally to the a Ethereum JSON RPC API endpoint
  *
+ * @internal
  * @param url the URL to send the request to
- * @param body the body data (JSON) to send with the request
+ * @param body JSON POST body
  * @returns the JSON response from the server
  * @example
  * ```javascript
@@ -59,6 +60,7 @@ type RPCMethodName =
 /**
  * Prepares data to be sent using the {@link post} function. Data is prepared per the {@link https://en.wikipedia.org/wiki/JSON-RPC#Examples JSON RPC v2 spec}
  *
+ * @internal
  * @param method the RPC method to be invoked
  * @param params the parameters to be passed to the defined method
  * @returns a POST method body matching the {@link https://en.wikipedia.org/wiki/JSON-RPC#Examples JSON RPC v2 spec}
@@ -74,6 +76,7 @@ type RPCMethodName =
 export function buildRPCPostBody(method: RPCMethodName, params: unknown[]) {
   return {
     jsonrpc: '2.0',
+    // TODO: Increment ID will be needed when websocket support is added
     id: 1,
     method,
     params,