refactor(network-controller): improve RPC service chain configuration

- Simplify RPC service configuration creation using map
- Update CHANGELOG with corrected event payload documentation
- Fix test descriptions for clarity
- Remove unused RpcServiceConfiguration type

Author: cryptodev-2s

packages/network-controller/CHANGELOG.md

@@ -20,9 +20,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - The event payloads for all events have been changed as well: `failoverEndpointUrl` has been renamed to `endpointUrl`, and `endpointUrl` has been renamed to `primaryEndpointUrl`. In addition, `networkClientId` has been added to the payload.
 - **BREAKING:** Rename and update payload data for `NetworkController:rpcEndpointRequestRetried` ([#7166](https://github.com/MetaMask/core/pull/7166))
   - This event is now called `NetworkController:rpcEndpointRetried`.
-  - The event payload has been changed as well: `failoverEndpointUrl` has been renamed to `endpointUrl`, and `endpointUrl` has been renamed to `primaryEndpointUrl`. In addition, `networkClientId` and `attempt` have been added to the payload.
+  - The event payload has been changed as well: `failoverEndpointUrl` has been removed, and `primaryEndpointUrl` has been added. In addition, `networkClientId` and `attempt` have been added to the payload.
 - **BREAKING:** Update `AbstractRpcService`/`RpcServiceRequestable` to remove `{ isolated: true }` from the `onBreak` event data type ([#7166](https://github.com/MetaMask/core/pull/7166))
-  - This represented the error produced when `isolate` is called on a Cockatiel circuit breaker policy, which we don't do (at least, not in the way it is designed to be called)
+  - This represented the error produced when `isolate` is called on a Cockatiel circuit breaker policy. This never happens for our service (we use `isolate` internally, but this error is suppressed and cannot trigger `onBreak`)
 - Move peer dependencies for controller and service packages to direct dependencies ([#7209](https://github.com/MetaMask/core/pull/7209))
   - The dependencies moved are:
     - `@metamask/error-reporting-service` (^3.0.0)

packages/network-controller/src/create-network-client.ts

@@ -207,11 +207,11 @@ function createRpcServiceChain({
   const availableEndpointUrls: [string, ...string[]] = isRpcFailoverEnabled
     ? [primaryEndpointUrl, ...(configuration.failoverRpcUrls ?? [])]
     : [primaryEndpointUrl];
-  const buildRpcServiceConfiguration = (endpointUrl: string) => ({
+  const rpcServiceConfigurations = availableEndpointUrls.map((endpointUrl) => ({
     ...getRpcServiceOptions(endpointUrl),
     endpointUrl,
     logger,
-  });
+  }));
 
   const getError = (value: object) => {
     if ('error' in value) {
@@ -223,8 +223,8 @@ function createRpcServiceChain({
   };
 
   const rpcServiceChain = new RpcServiceChain([
-    buildRpcServiceConfiguration(availableEndpointUrls[0]),
-    ...availableEndpointUrls.slice(1).map(buildRpcServiceConfiguration),
+    rpcServiceConfigurations[0],
+    ...rpcServiceConfigurations.slice(1),
   ]);
 
   rpcServiceChain.onBreak(

packages/network-controller/src/rpc-service/rpc-service-chain.test.ts

@@ -975,7 +975,7 @@ describe('RpcServiceChain', () => {
       await expect(rpcServiceChain.request(jsonRpcRequest)).rejects.toThrow(
         expectedError,
       );
-      // Retry the second endpoint for a third time, until max retries is hit.
+      // Retry the third endpoint for a third time, until max retries is hit.
       // The circuit will break on the last time.
       await expect(rpcServiceChain.request(jsonRpcRequest)).rejects.toThrow(
         expectedError,
@@ -1251,7 +1251,7 @@ describe('RpcServiceChain', () => {
       });
     });
 
-    it("calls onDegraded again when a service's underlying circuit breaks, and then after waiting, the service responds successfully but slowly", async () => {
+    it('calls onDegraded again when the service chain becomes unavailable, and then after waiting, the failover service responds successfully but slowly', async () => {
       const endpointUrl = 'https://some.endpoint';
       nock(endpointUrl)
         .post('/', {

packages/network-controller/src/rpc-service/rpc-service-chain.ts

@@ -37,8 +37,6 @@ const STATUSES = {
  */
 type Status = (typeof STATUSES)[keyof typeof STATUSES];
 
-type RpcServiceConfiguration = Omit<RpcServiceOptions, 'failoverService'>;
-
 /**
  * This class constructs and manages requests to a chain of RpcService objects
  * which represent RPC endpoints with which to access a particular network. The
@@ -93,10 +91,7 @@ export class RpcServiceChain {
    * {@link RpcServiceOptions}.
    */
   constructor(
-    rpcServiceConfigurations: [
-      RpcServiceConfiguration,
-      ...RpcServiceConfiguration[],
-    ],
+    rpcServiceConfigurations: [RpcServiceOptions, ...RpcServiceOptions[]],
   ) {
     this.#services = rpcServiceConfigurations.map(
       (rpcServiceConfiguration) => new RpcService(rpcServiceConfiguration),