Replace obsolete `notNull` helper with `!` operator

src/sidebar/components/ShareAnnotationsPanel.tsx

@@ -12,7 +12,6 @@ import { withServices } from '../service-context';
 import type { ToastMessengerService } from '../services/toast-messenger';
 import { useSidebarStore } from '../store';
 import { copyText } from '../util/copy-to-clipboard';
-import { notNull } from '../util/typing';
 import ShareLinks from './ShareLinks';
 import SidebarPanel from './SidebarPanel';
 
@@ -68,7 +67,7 @@ function ShareAnnotationsPanel({ toastMessenger }: ShareAnnotationPanelProps) {
                 className="text-color-text font-medium"
                 data-testid="sharing-intro"
               >
-                {notNull(focusedGroup).type === 'private' ? (
+                {focusedGroup!.type === 'private' ? (
                   <p>
                     Use this link to share these annotations with other group
                     members:
@@ -94,16 +93,16 @@ function ShareAnnotationsPanel({ toastMessenger }: ShareAnnotationPanelProps) {
                 </InputGroup>
               </div>
               <p data-testid="sharing-details">
-                {notNull(focusedGroup).type === 'private' ? (
+                {focusedGroup!.type === 'private' ? (
                   <span>
                     Annotations in the private group{' '}
-                    <em>{notNull(focusedGroup).name}</em> are only visible to
-                    group members.
+                    <em>{focusedGroup.name}</em> are only visible to group
+                    members.
                   </span>
                 ) : (
                   <span>
                     Anyone using this link may view the annotations in the group{' '}
-                    <em>{notNull(focusedGroup).name}</em>.
+                    <em>{focusedGroup.name}</em>.
                   </span>
                 )}{' '}
                 <span>

src/sidebar/helpers/thread.ts

 import type { Annotation } from '../../types/api';
-import { notNull } from '../util/typing';
 import type { Thread } from './build-thread';
 
 /**
@@ -63,7 +62,7 @@ export function rootAnnotations(threads: Thread[]): Annotation[] {
   // those annotations
   const threadAnnotations = threads
     .filter(thread => !!thread.annotation)
-    .map(thread => notNull(thread.annotation));
+    .map(thread => thread.annotation!);
 
   if (threadAnnotations.length) {
     return threadAnnotations;

src/sidebar/util/typing.js

-/**
- * Helper function for cases in which logically a reference is definitely
- * not nullish, but TS can't infer that correctly. This will cast the `arg`
- * and appease type-checking.
- *
- * @template T
- * @param {T} arg
- */
-export function notNull(arg) {
-  return /** @type {NonNullable<T>} */ (arg);
-}