Improved flexibility of FetchMiddleware for Web3.js

web3.js/src/connection.ts

@@ -761,27 +761,6 @@ function createRpcClient(
     agentManager = new AgentManager(useHttps);
   }
 
-  let fetchWithMiddleware:
-    | ((url: string, options: any) => Promise<Response>)
-    | undefined;
-
-  if (fetchMiddleware) {
-    fetchWithMiddleware = async (url: string, options: any) => {
-      const modifiedFetchArgs = await new Promise<[string, any]>(
-        (resolve, reject) => {
-          try {
-            fetchMiddleware(url, options, (modifiedUrl, modifiedOptions) =>
-              resolve([modifiedUrl, modifiedOptions]),
-            );
-          } catch (error) {
-            reject(error);
-          }
-        },
-      );
-      return await fetch(...modifiedFetchArgs);
-    };
-  }
-
   const clientBrowser = new RpcClient(async (request, callback) => {
     const agent = agentManager ? agentManager.requestStart() : undefined;
     const options = {
@@ -801,8 +780,8 @@ function createRpcClient(
       let res: Response;
       let waitTime = 500;
       for (;;) {
-        if (fetchWithMiddleware) {
-          res = await fetchWithMiddleware(url, options);
+        if (fetchMiddleware) {
+          res = await fetchMiddleware(url, options);
         } else {
           res = await fetch(url, options);
         }
@@ -1988,9 +1967,8 @@ export type HttpHeaders = {[header: string]: string};
  */
 export type FetchMiddleware = (
   url: string,
-  options: any,
-  fetch: (modifiedUrl: string, modifiedOptions: any) => void,
-) => void;
+  options: any
+) => Promise<Response>;
 
 /**
  * Configuration for instantiating a Connection

web3.js/test/connection.test.ts

@@ -3,7 +3,7 @@ import {Buffer} from 'buffer';
 import {Token, u64} from '@solana/spl-token';
 import {expect, use} from 'chai';
 import chaiAsPromised from 'chai-as-promised';
-
+import fetch from 'cross-fetch';
 import {
   Account,
   Authorized,
@@ -112,11 +112,11 @@ describe('Connection', () => {
 
     it('should allow middleware to augment request', async () => {
       let connection = new Connection(url, {
-        fetchMiddleware: (url, options, fetch) => {
+        fetchMiddleware: async (url, options) => {
           options.headers = Object.assign(options.headers, {
             Authorization: 'Bearer 123',
           });
-          fetch(url, options);
+          return await fetch(url, options);
         },
       });
 
@@ -136,7 +136,7 @@ describe('Connection', () => {
   it('should attribute middleware fatals to the middleware', async () => {
     let connection = new Connection(url, {
       // eslint-disable-next-line @typescript-eslint/no-unused-vars
-      fetchMiddleware: (_url, _options, _fetch) => {
+      fetchMiddleware: (_url, _options) => {
         throw new Error('This middleware experienced a fatal error');
       },
     });
@@ -151,8 +151,8 @@ describe('Connection', () => {
 
   it('should not attribute fetch errors to the middleware', async () => {
     let connection = new Connection(url, {
-      fetchMiddleware: (url, _options, fetch) => {
-        fetch(url, 'An `Object` was expected here; this is a `TypeError`.');
+      fetchMiddleware: async (url, _options) => {
+        return await fetch(url, 'An `Object` was expected here; this is a `TypeError`.' as RequestInit);
       },
     });
     const error = await expect(connection.getVersion()).to.be.rejected;