feat: add Monad Testnet to network-controller and controller-utils (#5724)

## Explanation

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This PR is to add Monad Testnet as default network on
`network-controller` default state - `networkConfigurationsByChainId`
with the constants and type from the latest `controller-utils`

### Changes:

- Refactor `network-controller`
methods`getDefaultCustomNetworkConfigurationsByChainId` to build the
configuration from `CustomNetworkType` instead of hardcode network 1 by
1

- Add `Monad Testnet` info into `controller-utils`
- Include `Monad Testnet` into `network-controller` method
`getDefaultCustomNetworkConfigurationsByChainId`

Integration PR in mobile:
MetaMask/metamask-mobile#14963

<img width="300" alt="image"
src="https://github.com/user-attachments/assets/5f4b5bd7-d4f2-4edb-9e03-43b08206276a"
/>


## References

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## Changelog

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## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

Author: stanleyyconsensys

packages/controller-utils/CHANGELOG.md

@@ -7,6 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add Monad Testnet to various constants, enums, and types ([#5724](https://github.com/MetaMask/core/pull/5724))
+  - Add `monad-testnet` to `BUILT_IN_NETWORKS`
+  - Add `monad-testnet` and `megaeth-testnet` to `BUILT_IN_CUSTOM_NETWORKS_RPC`
+  - Add `MonadTestnet` to `BuiltInNetworkName` enum
+  - Add `monad-testnet` to `ChainId` type
+  - Add `MonadTestnet` to `NetworksTicker` enum
+  - Add `MonadTestnet` to `BlockExplorerUrl` quasi-enum
+  - Add `MonadTestnet` to `NetworkNickname` quasi-enum
+
 ## [11.7.0]
 
 ### Added

packages/controller-utils/src/constants.ts

@@ -56,7 +56,12 @@ export const TESTNET_TICKER_SYMBOLS = {
  * Map of all built-in custom networks to their RPC endpoints.
  */
 export const BUILT_IN_CUSTOM_NETWORKS_RPC = {
+  /**
+   * @deprecated Please use `megaeth-testnet` instead.
+   */
   MEGAETH_TESTNET: 'https://carrot.megaeth.com/rpc',
+  'megaeth-testnet': 'https://carrot.megaeth.com/rpc',
+  'monad-testnet': 'https://testnet-rpc.monad.xyz',
 };
 
 /**
@@ -112,6 +117,13 @@ export const BUILT_IN_NETWORKS = {
       blockExplorerUrl: BlockExplorerUrl['megaeth-testnet'],
     },
   },
+  [NetworkType['monad-testnet']]: {
+    chainId: ChainId['monad-testnet'],
+    ticker: NetworksTicker['monad-testnet'],
+    rpcPrefs: {
+      blockExplorerUrl: BlockExplorerUrl['monad-testnet'],
+    },
+  },
   [NetworkType.rpc]: {
     chainId: undefined,
     blockExplorerUrl: undefined,

packages/controller-utils/src/types.ts

@@ -18,6 +18,7 @@ export type InfuraNetworkType =
  */
 export const CustomNetworkType = {
   'megaeth-testnet': 'megaeth-testnet',
+  'monad-testnet': 'monad-testnet',
 } as const;
 export type CustomNetworkType =
   (typeof CustomNetworkType)[keyof typeof CustomNetworkType];
@@ -76,6 +77,7 @@ export enum BuiltInNetworkName {
   LineaMainnet = 'linea-mainnet',
   Aurora = 'aurora',
   MegaETHTestnet = 'megaeth-testnet',
+  MonadTestnet = 'monad-testnet',
 }
 
 /**
@@ -92,6 +94,7 @@ export const ChainId = {
   [BuiltInNetworkName.LineaSepolia]: '0xe705', // toHex(59141)
   [BuiltInNetworkName.LineaMainnet]: '0xe708', // toHex(59144)
   [BuiltInNetworkName.MegaETHTestnet]: '0x18c6', // toHex(6342)
+  [BuiltInNetworkName.MonadTestnet]: '0x279f', // toHex(10143)
 } as const;
 export type ChainId = (typeof ChainId)[keyof typeof ChainId];
 
@@ -109,6 +112,7 @@ export enum NetworksTicker {
   'linea-sepolia' = 'LineaETH',
   'linea-mainnet' = 'ETH',
   'megaeth-testnet' = 'MegaETH',
+  'monad-testnet' = 'MON',
   // TODO: Either fix this lint violation or explain why it's necessary to ignore.
   // eslint-disable-next-line @typescript-eslint/naming-convention
   rpc = '',
@@ -122,6 +126,7 @@ export const BlockExplorerUrl = {
   [BuiltInNetworkName.LineaSepolia]: 'https://sepolia.lineascan.build',
   [BuiltInNetworkName.LineaMainnet]: 'https://lineascan.build',
   [BuiltInNetworkName.MegaETHTestnet]: 'https://megaexplorer.xyz',
+  [BuiltInNetworkName.MonadTestnet]: 'https://testnet.monadexplorer.com',
 } as const satisfies Record<BuiltInNetworkType, string>;
 export type BlockExplorerUrl =
   (typeof BlockExplorerUrl)[keyof typeof BlockExplorerUrl];
@@ -134,6 +139,7 @@ export const NetworkNickname = {
   [BuiltInNetworkName.LineaSepolia]: 'Linea Sepolia',
   [BuiltInNetworkName.LineaMainnet]: 'Linea',
   [BuiltInNetworkName.MegaETHTestnet]: 'Mega Testnet',
+  [BuiltInNetworkName.MonadTestnet]: 'Monad Testnet',
 } as const satisfies Record<BuiltInNetworkType, string>;
 export type NetworkNickname =
   (typeof NetworkNickname)[keyof typeof NetworkNickname];

packages/network-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add Monad Testnet as default network ([#5724](https://github.com/MetaMask/core/pull/5724))
+
 ## [23.3.0]
 
 ### Added

packages/network-controller/src/NetworkController.ts

@@ -7,6 +7,7 @@ import { BaseController } from '@metamask/base-controller';
 import type { Partialize } from '@metamask/controller-utils';
 import {
   InfuraNetworkType,
+  CustomNetworkType,
   NetworkType,
   isSafeChainId,
   isInfuraNetworkType,
@@ -15,7 +16,6 @@ import {
   NetworkNickname,
   BUILT_IN_CUSTOM_NETWORKS_RPC,
   BUILT_IN_NETWORKS,
-  BuiltInNetworkName,
 } from '@metamask/controller-utils';
 import type { PollingBlockTrackerOptions } from '@metamask/eth-block-tracker';
 import EthQuery from '@metamask/eth-query';
@@ -728,25 +728,46 @@ function getDefaultCustomNetworkConfigurationsByChainId(): Record<
   Hex,
   NetworkConfiguration
 > {
-  const { ticker, rpcPrefs } =
-    BUILT_IN_NETWORKS[BuiltInNetworkName.MegaETHTestnet];
+  // Create the `networkConfigurationsByChainId` objects explicitly,
+  // Because it is not always guaranteed that the custom networks are included in the
+  // default networks.
   return {
-    [ChainId[BuiltInNetworkName.MegaETHTestnet]]: {
-      blockExplorerUrls: [rpcPrefs.blockExplorerUrl],
-      chainId: ChainId[BuiltInNetworkName.MegaETHTestnet],
-      defaultRpcEndpointIndex: 0,
-      defaultBlockExplorerUrlIndex: 0,
-      name: NetworkNickname[BuiltInNetworkName.MegaETHTestnet],
-      nativeCurrency: ticker,
-      rpcEndpoints: [
-        {
-          failoverUrls: [],
-          networkClientId: BuiltInNetworkName.MegaETHTestnet,
-          type: RpcEndpointType.Custom,
-          url: BUILT_IN_CUSTOM_NETWORKS_RPC.MEGAETH_TESTNET,
-        },
-      ],
-    },
+    [ChainId['megaeth-testnet']]: getCustomNetworkConfiguration(
+      CustomNetworkType['megaeth-testnet'],
+    ),
+    [ChainId['monad-testnet']]: getCustomNetworkConfiguration(
+      CustomNetworkType['monad-testnet'],
+    ),
+  };
+}
+
+/**
+ * Constructs a `NetworkConfiguration` object by `CustomNetworkType`.
+ *
+ * @param customNetworkType - The type of the custom network.
+ * @returns The `NetworkConfiguration` object.
+ */
+function getCustomNetworkConfiguration(
+  customNetworkType: CustomNetworkType,
+): NetworkConfiguration {
+  const { ticker, rpcPrefs } = BUILT_IN_NETWORKS[customNetworkType];
+  const rpcEndpointUrl = BUILT_IN_CUSTOM_NETWORKS_RPC[customNetworkType];
+
+  return {
+    blockExplorerUrls: [rpcPrefs.blockExplorerUrl],
+    chainId: ChainId[customNetworkType],
+    defaultRpcEndpointIndex: 0,
+    defaultBlockExplorerUrlIndex: 0,
+    name: NetworkNickname[customNetworkType],
+    nativeCurrency: ticker,
+    rpcEndpoints: [
+      {
+        failoverUrls: [],
+        networkClientId: customNetworkType,
+        type: RpcEndpointType.Custom,
+        url: rpcEndpointUrl,
+      },
+    ],
   };
 }
 

packages/network-controller/src/types.ts

@@ -1,4 +1,4 @@
-import type { ChainId, InfuraNetworkType } from '@metamask/controller-utils';
+import type { InfuraNetworkType, ChainId } from '@metamask/controller-utils';
 import type { BlockTracker as BaseBlockTracker } from '@metamask/eth-block-tracker';
 import type { SafeEventEmitterProvider } from '@metamask/eth-json-rpc-provider';
 import type { Hex } from '@metamask/utils';
@@ -57,4 +57,6 @@ export type NetworkClientConfiguration =
 /**
  * The Chain ID representing the additional networks to be included as default.
  */
-export type AdditionalDefaultNetwork = (typeof ChainId)['megaeth-testnet'];
+export type AdditionalDefaultNetwork = (typeof ChainId)[
+  | 'megaeth-testnet'
+  | 'monad-testnet'];