chore: Notification services eslint cleanup (#7482)

## Explanation

* **What is the current state of things and why does it need to
change?**
The `notification-services-controller` package had several ESLint
suppressions in `eslint-suppressions.json` for rules such as
`@typescript-eslint/explicit-function-return-type`, `id-length`,
`id-denylist`, and `no-param-reassign`. These suppressions indicated
deviations from our established linting standards, affecting code
readability, maintainability, and type safety.
*   **What is the solution your changes offer and how does it work?**
This PR resolves all identified ESLint violations in
`process-notifications.ts`, `api-notifications.ts`, and
`feature-announcements.test.ts`.
* **`@typescript-eslint/explicit-function-return-type`**: Explicit
return types were added to functions for improved type safety and
clarity.
* **`id-length` and `id-denylist`**: Short or disallowed variable names
were refactored to be more descriptive, enhancing readability.
* **`no-param-reassign`**: Code was refactored to avoid reassigning
function parameters, promoting immutability and preventing unexpected
side effects.
After fixing the code, the corresponding entries were removed from
`eslint-suppressions.json`.
* **Are there any changes whose purpose might not obvious to those
unfamiliar with the domain?**
* For `id-length`, many single-character variables (e.g., `n`, `a`, `r`)
were expanded to full, descriptive names (e.g., `notification`, `addr`,
`response`).
* For `no-param-reassign`, new variables were introduced to hold
modified data instead of directly altering the original function
parameters.
* For `explicit-function-return-type`, specific types like `never` for
exhaustive checks and `Promise<void>` for async functions were added
where appropriate.

## References

* Fixes
[ASSETS-2100](https://consensyssoftware.atlassian.net/browse/ASSETS-2100)

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] 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)
- [ ] I've introduced [breaking
changes](https://github.com/MetaMask/core/tree/main/docs/breaking-changes.md)
in this PR and have prepared draft pull requests for clients and
consumer packages to resolve them

---
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[ASSETS-2100]:
https://consensyssoftware.atlassian.net/browse/ASSETS-2100?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Cleans up notification-services-controller by adding explicit return
types, renaming short variables, avoiding parameter reassignment, and
removing corresponding ESLint suppressions.
> 
> - **Notification processing (`processors/process-notifications.ts`)**:
> - Add explicit return types to type guards and helpers (including
`never` for exhaustive check).
> - Rename variables for clarity (`n` → `notification`, etc.) and
tighten generics (`isNotUndefined`).
> - Refactor `processAndFilterNotifications` to typed map/filter without
implicit any.
> - **API services (`services/api-notifications.ts`)**:
> - Add explicit return types to endpoint builders and async functions.
> - Avoid parameter reassignment by creating normalized copies of
address arrays; rename variables (`response`, `apiResponse`).
> - Minor comment/identifier cleanups (e.g., "Marks notifications as
read", catch `error`).
> - **Tests (`services/feature-announcements.test.ts`)**:
>   - Add explicit Promise return types to helpers; refine typings.
> - **ESLint**:
> - Remove suppressions for `process-notifications.ts`,
`api-notifications.ts`, and `feature-announcements.test.ts` in
`eslint-suppressions.json`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
d5f632d. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

Author: Prithpal-Sooriya

eslint-suppressions.json

@@ -1602,33 +1602,6 @@
       "count": 1
     }
   },
-  "packages/notification-services-controller/src/NotificationServicesController/processors/process-notifications.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 2
-    },
-    "id-length": {
-      "count": 6
-    }
-  },
-  "packages/notification-services-controller/src/NotificationServicesController/services/api-notifications.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 8
-    },
-    "id-denylist": {
-      "count": 1
-    },
-    "id-length": {
-      "count": 4
-    },
-    "no-param-reassign": {
-      "count": 2
-    }
-  },
-  "packages/notification-services-controller/src/NotificationServicesController/services/feature-announcements.test.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 2
-    }
-  },
   "packages/notification-services-controller/src/NotificationServicesController/services/feature-announcements.ts": {
     "@typescript-eslint/explicit-function-return-type": {
       "count": 2

packages/notification-services-controller/src/NotificationServicesController/processors/process-notifications.ts

@@ -17,18 +17,19 @@ import type { NormalisedAPINotification } from '../types/notification-api/notifi
 import type { RawSnapNotification } from '../types/snaps';
 
 const isOnChainNotification = (
-  n: RawNotificationUnion,
-): n is NormalisedAPINotification =>
-  NOTIFICATION_API_TRIGGER_TYPES_SET.has(n.type);
+  notification: RawNotificationUnion,
+): notification is NormalisedAPINotification =>
+  NOTIFICATION_API_TRIGGER_TYPES_SET.has(notification.type);
 
 const isFeatureAnnouncement = (
-  n: RawNotificationUnion,
-): n is FeatureAnnouncementRawNotification =>
-  n.type === TRIGGER_TYPES.FEATURES_ANNOUNCEMENT;
+  notification: RawNotificationUnion,
+): notification is FeatureAnnouncementRawNotification =>
+  notification.type === TRIGGER_TYPES.FEATURES_ANNOUNCEMENT;
 
 const isSnapNotification = (
-  n: RawNotificationUnion,
-): n is RawSnapNotification => n.type === TRIGGER_TYPES.SNAP;
+  notification: RawNotificationUnion,
+): notification is RawSnapNotification =>
+  notification.type === TRIGGER_TYPES.SNAP;
 
 /**
  * Process feature announcement and wallet notifications into a shared/normalised notification shape.
@@ -42,15 +43,18 @@ export function processNotification(
   notification: RawNotificationUnion,
   readNotifications: string[] = [],
 ): INotification {
-  const exhaustedAllCases = (_: never) => {
+  const exhaustedAllCases = (_uncheckedCase: never): never => {
     const type: string = notification?.type;
     throw new Error(`No processor found for notification kind ${type}`);
   };
 
   if (isFeatureAnnouncement(notification)) {
-    const n = processFeatureAnnouncement(notification);
-    n.isRead = isFeatureAnnouncementRead(n, readNotifications);
-    return n;
+    const processedNotification = processFeatureAnnouncement(notification);
+    processedNotification.isRead = isFeatureAnnouncementRead(
+      processedNotification,
+      readNotifications,
+    );
+    return processedNotification;
   }
 
   if (isSnapNotification(notification)) {
@@ -86,8 +90,11 @@ export function safeProcessNotification(
   }
 }
 
-const isNotUndefined = <Item>(t?: Item): t is Item => Boolean(t);
+const isNotUndefined = <Item>(item?: Item): item is Item => Boolean(item);
 export const processAndFilterNotifications = (
-  ns: RawNotificationUnion[],
+  notifications: RawNotificationUnion[],
   readIds: string[],
-) => ns.map((n) => safeProcessNotification(n, readIds)).filter(isNotUndefined);
+): INotification[] =>
+  notifications
+    .map((notification) => safeProcessNotification(notification, readIds))
+    .filter(isNotUndefined);

packages/notification-services-controller/src/NotificationServicesController/services/api-notifications.ts

@@ -24,7 +24,7 @@ const TRIGGER_API_ENV = {
   prd: 'https://trigger.api.cx.metamask.io',
 } satisfies Record<ENV, string>;
 
-export const TRIGGER_API = (env: ENV = 'prd') =>
+export const TRIGGER_API = (env: ENV = 'prd'): string =>
   TRIGGER_API_ENV[env] ?? TRIGGER_API_ENV.prd;
 
 const NOTIFICATION_API_ENV = {
@@ -33,24 +33,26 @@ const NOTIFICATION_API_ENV = {
   prd: 'https://notification.api.cx.metamask.io',
 };
 
-export const NOTIFICATION_API = (env: ENV = 'prd') =>
+export const NOTIFICATION_API = (env: ENV = 'prd'): string =>
   NOTIFICATION_API_ENV[env] ?? NOTIFICATION_API_ENV.prd;
 
 // Gets notification settings for each account provided
-export const TRIGGER_API_NOTIFICATIONS_QUERY_ENDPOINT = (env: ENV = 'prd') =>
-  `${TRIGGER_API(env)}/api/v2/notifications/query`;
+export const TRIGGER_API_NOTIFICATIONS_QUERY_ENDPOINT = (
+  env: ENV = 'prd',
+): string => `${TRIGGER_API(env)}/api/v2/notifications/query`;
 
 // Used to create/update account notifications for each account provided
-export const TRIGGER_API_NOTIFICATIONS_ENDPOINT = (env: ENV = 'prd') =>
+export const TRIGGER_API_NOTIFICATIONS_ENDPOINT = (env: ENV = 'prd'): string =>
   `${TRIGGER_API(env)}/api/v2/notifications`;
 
 // Lists notifications for each account provided
-export const NOTIFICATION_API_LIST_ENDPOINT = (env: ENV = 'prd') =>
+export const NOTIFICATION_API_LIST_ENDPOINT = (env: ENV = 'prd'): string =>
   `${NOTIFICATION_API(env)}/api/v3/notifications`;
 
-// Makrs notifications as read
-export const NOTIFICATION_API_MARK_ALL_AS_READ_ENDPOINT = (env: ENV = 'prd') =>
-  `${NOTIFICATION_API(env)}/api/v3/notifications/mark-as-read`;
+// Marks notifications as read
+export const NOTIFICATION_API_MARK_ALL_AS_READ_ENDPOINT = (
+  env: ENV = 'prd',
+): string => `${NOTIFICATION_API(env)}/api/v3/notifications/mark-as-read`;
 
 /**
  * fetches notification config (accounts enabled vs disabled)
@@ -66,31 +68,31 @@ export async function getNotificationsApiConfigCached(
   bearerToken: string,
   addresses: string[],
   env: ENV = 'prd',
-) {
+): Promise<{ address: string; enabled: boolean }[]> {
   if (addresses.length === 0) {
     return [];
   }
 
-  addresses = addresses.map((a) => a.toLowerCase());
+  const normalizedAddresses = addresses.map((addr) => addr.toLowerCase());
 
-  const cached = notificationsConfigCache.get(addresses);
+  const cached = notificationsConfigCache.get(normalizedAddresses);
   if (cached) {
     return cached;
   }
 
   type RequestBody = { address: string }[];
   type Response = { address: string; enabled: boolean }[];
-  const body: RequestBody = addresses.map((address) => ({ address }));
-  const data = await makeApiCall(
+  const body: RequestBody = normalizedAddresses.map((address) => ({ address }));
+  const apiResponse = await makeApiCall(
     bearerToken,
     TRIGGER_API_NOTIFICATIONS_QUERY_ENDPOINT(env),
     'POST',
     body,
   )
-    .then<Response | null>((r) => (r.ok ? r.json() : null))
+    .then<Response | null>((response) => (response.ok ? response.json() : null))
     .catch(() => null);
 
-  const result = data ?? [];
+  const result = apiResponse ?? [];
 
   if (result.length > 0) {
     notificationsConfigCache.set(result);
@@ -111,25 +113,25 @@ export async function updateOnChainNotifications(
   bearerToken: string,
   addresses: { address: string; enabled: boolean }[],
   env: ENV = 'prd',
-) {
+): Promise<void> {
   if (addresses.length === 0) {
     return;
   }
 
-  addresses = addresses.map((a) => {
-    a.address = a.address.toLowerCase();
-    return a;
-  });
+  const normalizedAddresses = addresses.map((item) => ({
+    ...item,
+    address: item.address.toLowerCase(),
+  }));
 
   type RequestBody = { address: string; enabled: boolean }[];
-  const body: RequestBody = addresses;
+  const body: RequestBody = normalizedAddresses;
   await makeApiCall(
     bearerToken,
     TRIGGER_API_NOTIFICATIONS_ENDPOINT(env),
     'POST',
     body,
   )
-    .then(() => notificationsConfigCache.set(addresses))
+    .then(() => notificationsConfigCache.set(normalizedAddresses))
     .catch(() => null);
 }
 
@@ -160,7 +162,7 @@ export async function getAPINotifications(
     Schema.paths['/api/v3/notifications']['post']['responses']['200']['content']['application/json'];
 
   const body: RequestBody = {
-    addresses: addresses.map((a) => a.toLowerCase()),
+    addresses: addresses.map((addr) => addr.toLowerCase()),
     locale,
     platform,
   };
@@ -170,23 +172,25 @@ export async function getAPINotifications(
     'POST',
     body,
   )
-    .then<APIResponse | null>((r) => (r.ok ? r.json() : null))
+    .then<APIResponse | null>((response) =>
+      response.ok ? response.json() : null,
+    )
     .catch(() => null);
 
   // Transform and sort notifications
   const transformedNotifications = notifications
-    ?.map((n): UnprocessedRawNotification | undefined => {
-      if (!n.notification_type) {
+    ?.map((notification): UnprocessedRawNotification | undefined => {
+      if (!notification.notification_type) {
         return undefined;
       }
 
       try {
-        return toRawAPINotification(n);
+        return toRawAPINotification(notification);
       } catch {
         return undefined;
       }
     })
-    .filter((n): n is NormalisedAPINotification => Boolean(n));
+    .filter((item): item is NormalisedAPINotification => Boolean(item));
 
   return transformedNotifications ?? [];
 }
@@ -223,7 +227,7 @@ export async function markNotificationsAsRead(
       'POST',
       body,
     );
-  } catch (err) {
-    log.error('Error marking notifications as read:', err);
+  } catch (error) {
+    log.error('Error marking notifications as read:', error);
   }
 }

packages/notification-services-controller/src/NotificationServicesController/services/feature-announcements.test.ts

@@ -33,7 +33,7 @@ describe('Feature Announcement Notifications', () => {
 
     const assertEnvEmpty = async (
       override: Partial<typeof featureAnnouncementsEnv>,
-    ) => {
+    ): Promise<void> => {
       const result = await getFeatureAnnouncementNotifications({
         ...featureAnnouncementsEnv,
         ...override,
@@ -125,7 +125,7 @@ describe('Feature Announcement Notifications', () => {
         minimumVersion: string | undefined,
         maximumVersion: string | undefined,
         platformVersion: string | undefined,
-      ) => {
+      ): Promise<INotification[]> => {
         const apiResponse = createMockFeatureAnnouncementAPIResult();
         if (apiResponse.items?.[0]) {
           apiResponse.items[0].fields.extensionMinimumVersionNumber = undefined;