refactor: remove unused testnet config for swaps (MetaMask#24244)

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## **Description**

In MM mobile, we define an array of allowed testnets for swaps. This is
consumed only on DEV env and is used by some utilities like
isSwapsAllowed. To complete the legacy migration we will have to take
care of those utilities (either remove or migrate) but before that, this
PR removes the dependency to testnets and reduce the tech debt of the
swaps module.

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CHANGELOG entry: null 

## **Related issues**

Fixes: https://consensyssoftware.atlassian.net/browse/SWAPS-3594

## **Manual testing steps**

```gherkin
This PR does not introduce any business logic change, just run a basic regression test to ensure swaps functionality is not affected.
```

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### **Before**

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### **After**

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## **Pre-merge author checklist**

- [x] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
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- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
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Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
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- [ ] I confirm that this PR addresses all acceptance criteria described
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as recordings and or screenshots.


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Removes testnet-specific swaps configuration and dev-only paths,
simplifying chain gating and feature flag handling for Swaps.
> 
> - Drops `SWAPS_TESTNET_CHAIN_ID` and `allowedTestnetChainIds`; removes
`__DEV__` and `ONLY_MAINNET` branching in `isSwapsAllowed`
> - Updates allowed chain lists in `UI/Swaps/utils` and
`Engine/constants` to include only supported mainnets and multichain
scopes
> - Simplifies `getFeatureFlagChainId` to identity and adjusts
liveness/feature flag mapping in `reducers/swaps`
> - Cleans up imports and removes unused constants
> - Updates unit tests to reflect removal of testnet logic and identity
`getFeatureFlagChainId`
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
fba3425. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: GeorgeGkas

app/components/UI/Swaps/utils/index.js

@@ -3,13 +3,8 @@ import BigNumber from 'bignumber.js';
 import { swapsUtils } from '@metamask/swaps-controller';
 import { strings } from '../../../../../locales/i18n';
 import AppConstants from '../../../../core/AppConstants';
-import { NETWORKS_CHAIN_ID } from '../../../../constants/network';
 import { SolScope, BtcScope, TrxScope } from '@metamask/keyring-api';
 import { CHAIN_IDS } from '@metamask/transaction-controller';
-import {
-  NATIVE_SWAPS_TOKEN_ADDRESS,
-  SWAPS_TESTNET_CHAIN_ID,
-} from '../../../../constants/bridge';
 import { isSwapsNativeAsset } from '../../../../util/bridge';
 
 const allowedChainIds = [
@@ -24,25 +19,12 @@ const allowedChainIds = [
   CHAIN_IDS.BASE,
   CHAIN_IDS.SEI,
   CHAIN_IDS.MONAD,
-  SWAPS_TESTNET_CHAIN_ID,
 ];
 
-export const allowedTestnetChainIds = [
-  NETWORKS_CHAIN_ID.GOERLI,
-  NETWORKS_CHAIN_ID.SEPOLIA,
-];
-
-if (__DEV__) {
-  allowedChainIds.push(...allowedTestnetChainIds);
-}
-
 export function isSwapsAllowed(chainId) {
   if (!AppConstants.SWAPS.ACTIVE) {
     return false;
   }
-  if (!AppConstants.SWAPS.ONLY_MAINNET) {
-    allowedChainIds.push(SWAPS_TESTNET_CHAIN_ID);
-  }
 
   if (
     chainId === SolScope.Mainnet ||

app/components/UI/Swaps/utils/index.test.js

@@ -4,7 +4,6 @@ import {
   isSwapsAllowed,
 } from './index';
 import { CHAIN_IDS } from '@metamask/transaction-controller';
-import { SWAPS_TESTNET_CHAIN_ID } from '../../../../constants/bridge';
 
 // Mock AppConstants
 const mockSwapsConstantsGetter = jest.fn(() => ({
@@ -221,24 +220,4 @@ describe('isSwapsAllowed', () => {
     const unsupportedChainId = '0x9999';
     expect(isSwapsAllowed(unsupportedChainId)).toBe(false);
   });
-
-  describe('testnet chain IDs', () => {
-    it('should return true for testnet chain IDs in development when ONLY_MAINNET is true', () => {
-      global.__DEV__ = true;
-      mockSwapsConstantsGetter.mockReturnValue({
-        ...mockSwapsConstantsGetter(),
-        ONLY_MAINNET: true,
-      });
-      expect(isSwapsAllowed(SWAPS_TESTNET_CHAIN_ID)).toBe(true);
-    });
-
-    it('should return true for testnet chain IDs when ONLY_MAINNET is false', () => {
-      global.__DEV__ = false;
-      mockSwapsConstantsGetter.mockReturnValue({
-        ...mockSwapsConstantsGetter(),
-        ONLY_MAINNET: false,
-      });
-      expect(isSwapsAllowed(SWAPS_TESTNET_CHAIN_ID)).toBe(true);
-    });
-  });
 });

app/constants/bridge.ts

@@ -6,12 +6,6 @@ import {
   BRIDGE_PROD_API_BASE_URL,
 } from '@metamask/bridge-controller';
 
-/**
- * Swaps testnet chain ID (1337 in decimal)
- * Used for testing swaps functionality on local/test networks
- */
-export const SWAPS_TESTNET_CHAIN_ID: Hex = '0x539';
-
 /**
  * Native token address (zero address)
  * Used to represent native tokens (ETH, BNB, MATIC, etc.) across all EVM chains

app/core/Engine/constants.ts

@@ -1,5 +1,4 @@
 import { CHAIN_IDS } from '@metamask/transaction-controller';
-import { SWAPS_TESTNET_CHAIN_ID } from '../../constants/bridge';
 
 /**
  * Messageable modules that are part of the Engine's context, but are not defined with state.
@@ -88,7 +87,6 @@ export const BACKGROUND_STATE_CHANGE_EVENT_NAMES = [
 export const swapsSupportedChainIds = [
   CHAIN_IDS.MAINNET,
   CHAIN_IDS.BSC,
-  SWAPS_TESTNET_CHAIN_ID,
   CHAIN_IDS.POLYGON,
   CHAIN_IDS.AVALANCHE,
   CHAIN_IDS.ARBITRUM,

app/reducers/swaps/index.js

@@ -2,34 +2,23 @@ import { createSelector } from 'reselect';
 import { isMainnetByChainId } from '../../util/networks';
 import { safeToChecksumAddress, areAddressesEqual } from '../../util/address';
 import { lte } from '../../util/lodash';
-import {
-  selectChainId,
-  selectEvmChainId,
-} from '../../selectors/networkController';
+import { selectEvmChainId } from '../../selectors/networkController';
 import {
   selectAllTokens,
   selectTokens,
 } from '../../selectors/tokensController';
 import { selectTokenList } from '../../selectors/tokenListController';
 import { selectContractBalances } from '../../selectors/tokenBalancesController';
-import { getChainFeatureFlags, getSwapsLiveness } from './utils';
-import { allowedTestnetChainIds } from '../../components/UI/Swaps/utils';
-import { NETWORKS_CHAIN_ID } from '../../constants/network';
+import { getSwapsLiveness } from './utils';
 import { selectSelectedInternalAccountAddress } from '../../selectors/accountsController';
 import { CHAIN_ID_TO_NAME_MAP } from '@metamask/swaps-controller/dist/constants';
 import { invert, omit } from 'lodash';
 import { createDeepEqualSelector } from '../../selectors/util';
 import { toHex } from '@metamask/controller-utils';
-import { SolScope } from '@metamask/keyring-api';
-
-// If we are in dev and on a testnet, just use mainnet feature flags,
-// since we don't have feature flags for testnets in the API
-export const getFeatureFlagChainId = (chainId) =>
-  typeof __DEV__ !== 'undefined' &&
-  __DEV__ &&
-  allowedTestnetChainIds.includes(chainId)
-    ? NETWORKS_CHAIN_ID.MAINNET
-    : chainId;
+
+// Identity function, will be removed when legacy swaps is removed,
+// but keep it for now to keep changes atomic.
+export const getFeatureFlagChainId = (chainId) => chainId;
 
 // * Constants
 export const SWAPS_SET_LIVENESS = 'SWAPS_SET_LIVENESS';

app/reducers/swaps/swaps.test.ts

@@ -4,7 +4,6 @@ import Device from '../../util/device';
 import { NetworkClientType } from '@metamask/network-controller';
 // eslint-disable-next-line import/no-namespace
 import * as tokensControllerSelectors from '../../selectors/tokensController';
-import { NETWORKS_CHAIN_ID } from '../../constants/network';
 import { FeatureFlags } from '@metamask/swaps-controller/dist/types';
 
 // Type definitions for the swaps reducer
@@ -42,15 +41,11 @@ interface SwapsState {
 }
 
 jest.mock('../../selectors/tokensController');
-jest.mock('../../components/UI/Swaps/utils', () => ({
-  allowedTestnetChainIds: ['0xaa36a7'], // Sepolia testnet
-}));
 jest.mock('@metamask/swaps-controller/dist/constants', () => ({
   CHAIN_ID_TO_NAME_MAP: {
     '0x1': 'ethereum',
     '0x38': 'bsc',
     '0x89': 'polygon',
-    '0xaa36a7': 'sepolia',
   },
 }));
 
@@ -111,16 +106,6 @@ const DEFAULT_FEATURE_FLAGS = {
 } as unknown as FeatureFlags;
 
 describe('swaps reducer', () => {
-  const withGlobalDev = (devValue: boolean, testFn: () => void) => {
-    const originalDev = (global as { __DEV__?: boolean }).__DEV__;
-    (global as { __DEV__?: boolean }).__DEV__ = devValue;
-    try {
-      testFn();
-    } finally {
-      (global as { __DEV__?: boolean }).__DEV__ = originalDev;
-    }
-  };
-
   it('should return initial state', () => {
     const state = reducer(undefined, emptyAction);
     expect(state).toEqual(initialState);
@@ -299,30 +284,6 @@ describe('swaps reducer', () => {
       ).toEqual(DEFAULT_FEATURE_FLAGS.bsc);
     });
 
-    it('should handle testnet chain IDs in dev mode', () => {
-      withGlobalDev(true, () => {
-        const initalState = reducer(undefined, emptyAction);
-        const action: SetLivenessAction = {
-          type: SWAPS_SET_LIVENESS,
-          payload: {
-            featureFlags: DEFAULT_FEATURE_FLAGS,
-            chainId: '0xaa36a7', // Sepolia testnet
-          },
-        };
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        const liveState = reducer(initalState as any, action) as SwapsState;
-
-        // Should use mainnet feature flags for testnet
-        expect(liveState['0x1'].featureFlags).toEqual(
-          DEFAULT_FEATURE_FLAGS.ethereum,
-        );
-        // Should also set the testnet chain with mainnet flags
-        expect(
-          (liveState['0xaa36a7'] as { featureFlags?: unknown }).featureFlags,
-        ).toEqual(DEFAULT_FEATURE_FLAGS.ethereum);
-      });
-    });
-
     it('should preserve existing state when updating feature flags', () => {
       const existingState = {
         ...initialState,
@@ -404,25 +365,16 @@ describe('swaps reducer', () => {
   });
 
   describe('getFeatureFlagChainId', () => {
-    it('should return mainnet chain ID for testnets in dev mode', () => {
-      withGlobalDev(true, () => {
-        const result = getFeatureFlagChainId('0xaa36a7'); // Sepolia
-        expect(result).toBe(NETWORKS_CHAIN_ID.MAINNET);
-      });
-    });
+    it('returns the same chain ID without modification', () => {
+      const result = getFeatureFlagChainId('0x1');
 
-    it('should return original chain ID for non-testnets', () => {
-      withGlobalDev(true, () => {
-        const result = getFeatureFlagChainId('0x38'); // BSC
-        expect(result).toBe('0x38');
-      });
+      expect(result).toBe('0x1');
     });
 
-    it('should return original chain ID when not in dev mode', () => {
-      withGlobalDev(false, () => {
-        const result = getFeatureFlagChainId('0xaa36a7'); // Sepolia
-        expect(result).toBe('0xaa36a7');
-      });
+    it('returns the same chain ID for any input', () => {
+      const result = getFeatureFlagChainId('0x38');
+
+      expect(result).toBe('0x38');
     });
   });