Chore/better lint rules v3

app/[locale]/admin/sellers/create/page.tsx

@@ -122,7 +122,7 @@ export default function CreateSellerPage() {
 
   const updateField = (field: keyof FormState, value: string) => {
     setForm((prev) => ({ ...prev, [field]: value }));
-    if (errors[field]) {
+    if (Object.hasOwn(errors, field)) {
       setErrors((prev) => {
         const next = { ...prev };
         delete next[field];
@@ -158,9 +158,9 @@ export default function CreateSellerPage() {
 
       router.push(`/${locale}/admin/sellers`);
       router.refresh();
-    } catch (err: unknown) {
+    } catch (error: unknown) {
       setServerError(
-        err instanceof Error ? err.message : dict.admin.createSellerError,
+        error instanceof Error ? error.message : dict.admin.createSellerError,
       );
     } finally {
       setLoading(false);

app/[locale]/admin/sellers/page.tsx

@@ -165,8 +165,8 @@ export default async function AdminSellersPage({
             defaultValue={filter.q ?? ''}
             hiddenFields={{
               pageSize: String(pageSize),
-              ...(filter.sortBy ? { sortBy: filter.sortBy } : {}),
-              ...(filter.sortDir ? { sortDir: filter.sortDir } : {}),
+              ...(filter.sortBy && { sortBy: filter.sortBy }),
+              ...(filter.sortDir && { sortDir: filter.sortDir }),
             }}
           />
         </div>
@@ -195,8 +195,10 @@ export default async function AdminSellersPage({
             prevLabel={dict.admin.pagePrev}
             nextLabel={dict.admin.pageNext}
             pageInfo={dict.admin.pageXofY
-              .replace('{current}', String(currentPage))
-              .replace('{total}', String(totalPages))}
+              .split('{current}')
+              .join(currentPage.toString())
+              .split('{total}')
+              .join(totalPages.toString())}
           />
         </>
       )}

app/[locale]/auth/change-password/page.tsx

@@ -65,9 +65,11 @@ export default function ChangePasswordPage() {
       setCurrentPassword('');
       setNewPassword('');
       setConfirmPassword('');
-    } catch (err: unknown) {
+    } catch (error_: unknown) {
       setError(
-        err instanceof Error ? err.message : dict.auth.failedToChangePassword,
+        error_ instanceof Error
+          ? error_.message
+          : dict.auth.failedToChangePassword,
       );
     } finally {
       setLoading(false);

app/[locale]/auth/reset-password/page.tsx

@@ -20,7 +20,7 @@ export default function ResetPasswordPage() {
   const [newPassword, setNewPassword] = useState('');
   const [confirmPassword, setConfirmPassword] = useState('');
   const [error, setError] = useState<string | null>(() =>
-    !token ? dict.auth.tokenExpired : null,
+    token ? null : dict.auth.tokenExpired,
   );
   const [loading, setLoading] = useState(false);
   const [success, setSuccess] = useState(false);
@@ -64,9 +64,11 @@ export default function ResetPasswordPage() {
       }
       setSuccess(true);
       router.push('/');
-    } catch (err: unknown) {
+    } catch (error_: unknown) {
       setError(
-        err instanceof Error ? err.message : dict.auth.failedToResetPassword,
+        error_ instanceof Error
+          ? error_.message
+          : dict.auth.failedToResetPassword,
       );
     } finally {
       setLoading(false);

app/[locale]/auth/signup/page.tsx

@@ -61,7 +61,7 @@ function applyIssue(errors: FormErrors, issue: ZodIssue) {
     }
     default: {
       if (path.startsWith('address.')) {
-        const addrField = path.split('.')[1] as keyof AddressFields;
+        const addrField = path.split('.', 2)[1] as keyof AddressFields;
         if (!errors.address) errors.address = {};
         errors.address[addrField] = issue.message;
       }
@@ -125,7 +125,7 @@ export default function SignUpPage() {
 
   const updateField = (field: keyof FormState, value: string) => {
     setForm((prev) => ({ ...prev, [field]: value }));
-    if (errors[field]) {
+    if (Object.hasOwn(errors, field)) {
       setErrors((prev) => {
         const next = { ...prev };
         delete next[field];
@@ -139,7 +139,7 @@ export default function SignUpPage() {
       ...prev,
       address: { ...prev.address, [field]: value },
     }));
-    if (errors.address?.[field]) {
+    if (errors.address?.[field] !== undefined) {
       setErrors((prev) => {
         const next = {
           ...prev,
@@ -210,9 +210,9 @@ export default function SignUpPage() {
         // Fallback: redirect to sign-in if auto-login fails
         router.push(`/${locale}/auth/signin?registered=true`);
       }
-    } catch (err: unknown) {
+    } catch (error: unknown) {
       setServerError(
-        err instanceof Error ? err.message : 'An unexpected error occurred',
+        error instanceof Error ? error.message : 'An unexpected error occurred',
       );
     } finally {
       setLoading(false);

app/[locale]/auth/verify-email/page.tsx

@@ -12,7 +12,7 @@ export default function VerifyEmailPage() {
   const token = searchParams.get('token');
   const [status, setStatus] = useState<
     'loading' | 'success' | 'expired' | 'invalid'
-  >(() => (!token ? 'invalid' : 'loading'));
+  >(() => (token ? 'loading' : 'invalid'));
   const dict = useDictionary();
 
   useEffect(() => {
@@ -22,22 +22,26 @@ export default function VerifyEmailPage() {
 
     const controller = new AbortController();
 
-    fetch(`/api/auth/verify-email?token=${encodeURIComponent(token)}`, {
-      signal: controller.signal,
-    })
-      .then((res) => res.json())
-      .then((data) => {
+    (async () => {
+      try {
+        const res = await fetch(
+          `/api/auth/verify-email?token=${encodeURIComponent(token)}`,
+          {
+            signal: controller.signal,
+          },
+        );
+        const data = await res.json();
         if (data.success) {
           setStatus('success');
         } else if (data.error?.includes('expired')) {
           setStatus('expired');
         } else {
           setStatus('invalid');
         }
-      })
-      .catch(() => {
+      } catch {
         setStatus('invalid');
-      });
+      }
+    })();
 
     return () => controller.abort();
   }, [token]);

app/[locale]/cart/design-preview.tsx

@@ -32,15 +32,15 @@ export function DesignPreview({
   const canvasRef = useRef<HTMLCanvasElement | null>(null);
 
   useEffect(() => {
-    let cancelled = false;
+    let isCancelled = false;
 
     async function draw() {
       const c = canvasRef.current?.getContext('2d');
       if (!c) return;
 
       const productImg = await loadImage(productImageUrl);
       const designImg = await loadImage(designImageUrl);
-      if (cancelled) return;
+      if (isCancelled) return;
 
       c.clearRect(0, 0, width, height);
       c.fillStyle = '#f4f2e6';
@@ -63,7 +63,7 @@ export function DesignPreview({
     draw();
 
     return () => {
-      cancelled = true;
+      isCancelled = true;
     };
   }, [productImageUrl, designImageUrl, designPosition, width, height]);
 

app/[locale]/checkout/page.tsx

@@ -209,7 +209,7 @@ export default async function CheckoutPage({
                     <span className={styles.itemCustomization}>
                       {[
                         ...item.customizations.flatMap((c) => [
-                          c.size &&
+                          c.size != null &&
                             `${dict.common.customizationSize}: ${c.size}`,
                           c.color &&
                             `${dict.common.customizationColor}: ${c.color}`,
@@ -260,10 +260,9 @@ export default async function CheckoutPage({
           {isFirstPurchase && (
             <div className={styles.totalRow}>
               <span>
-                {dict.common.firstPurchaseDiscount.replace(
-                  '{rate}',
-                  String(FIRST_PURCHASE_DISCOUNT_RATE * 100),
-                )}
+                {dict.common.firstPurchaseDiscount
+                  .split('{rate}')
+                  .join((FIRST_PURCHASE_DISCOUNT_RATE * 100).toString())}
               </span>
               <span className={styles.discount}>
                 −{Money.format(discount, currency)}

app/[locale]/layout.tsx

@@ -94,12 +94,12 @@ export default async function RootLayout({
   // ADMIN/DESIGNER and have no orders
   const role = (session?.user as { role?: string } | undefined)?.role;
   const isInternal = role === ADMIN_ROLE || role === DESIGNER_ROLE;
-  let showBanner = !isInternal;
-  if (showBanner && session?.user?.id) {
+  let isShowBanner = !isInternal;
+  if (isShowBanner && session?.user?.id) {
     const orderCount = await prisma.order.count({
       where: { userId: session.user.id },
     });
-    showBanner = orderCount === 0;
+    isShowBanner = orderCount === 0;
   }
 
   return (
@@ -142,7 +142,7 @@ export default async function RootLayout({
                 </div>
               </header>
 
-              {showBanner && <HeaderBanner text={dict.common.promoBanner} />}
+              {isShowBanner && <HeaderBanner text={dict.common.promoBanner} />}
 
               <main className={styles.main}>
                 <DictionaryProvider dict={dict}>

app/[locale]/orders/[orderId]/page.tsx

@@ -89,9 +89,9 @@ export default async function OrderDetailPage({
               )?.imageUrl;
               const displayImage = customImage ?? item.productImageUrl;
               const lineTotal =
-                item.unitPrice != null
-                  ? item.unitPrice * item.quantity
-                  : undefined;
+                item.unitPrice == null
+                  ? undefined
+                  : item.unitPrice * item.quantity;
 
               return (
                 <div key={item.id} className={styles.itemRow}>
@@ -113,7 +113,7 @@ export default async function OrderDetailPage({
                         <span className={styles.itemCustomization}>
                           {item.customizationSnapshot
                             .flatMap((c) => [
-                              c.size &&
+                              c.size != null &&
                                 `${dict.common.customizationSize}: ${c.size}`,
                               c.color &&
                                 `${dict.common.customizationColor}: ${c.color}`,

app/[locale]/orders/page.tsx

@@ -135,7 +135,7 @@ export default async function CustomerOrdersPage({
     if (filter.pageSize !== 20) params.set('pageSize', String(filter.pageSize));
     if (filter.q) params.set('q', filter.q);
     const qs = params.toString();
-    return `/${locale}/orders${qs ? `?${qs}` : ''}`;
+    return qs ? `/${locale}/orders?${qs}` : `/${locale}/orders`;
   };
 
   return (
@@ -153,7 +153,7 @@ export default async function CustomerOrdersPage({
               ariaLabel={dict.orders?.searchItems ?? 'Search by product'}
               defaultValue={filter.q}
               hiddenFields={
-                filter.status !== 'all' ? { status: filter.status } : undefined
+                filter.status === 'all' ? undefined : { status: filter.status }
               }
             />
           </div>

app/[locale]/page.tsx

@@ -47,16 +47,16 @@ export default async function HomePage({
   // Server-backed recent suggestions for authenticated users only.
   // v1 spec: guests receive null; no localStorage / sessionStorage / cookies
   // are ever written by the search feature.
-  const recent: RecentSearchSuggestion[] | null = session
-    ? await new GetRecentSearchesUseCase(container.getSearchHistoryRepository())
-        .execute({ userId: session.id, locale })
-        .then((entries) =>
-          entries.map((e) => ({
-            term: e.term,
-            searchedAt: e.searchedAt.toISOString(),
-          })),
-        )
-    : null;
+  let recent: RecentSearchSuggestion[] | null = null;
+  if (session) {
+    const entries = await new GetRecentSearchesUseCase(
+      container.getSearchHistoryRepository(),
+    ).execute({ userId: session.id, locale });
+    recent = entries.map((e) => ({
+      term: e.term,
+      searchedAt: e.searchedAt.toISOString(),
+    }));
+  }
 
   // Client island receives a stable JSON shape. We pre-format
   // the price string on the server so the client never receives

app/[locale]/products/[id]/customization-experience.tsx

@@ -94,7 +94,7 @@ function CustomizationExperienceInner({
   const { draft, setImage, setDesignPosition } = useCustomizationDraft();
   const customizationModel =
     ProductCustomizationConfig.fromJson(customizationConfig);
-  const allowsPhoto = customizationModel.allowPhotoDesign !== false;
+  const isAllowsPhoto = customizationModel.allowPhotoDesign !== false;
   const activeProductImageUrl =
     productImages.find((img) => img.alt === draft.color)?.url ??
     previewBaseImageUrl;
@@ -146,7 +146,7 @@ function CustomizationExperienceInner({
 
       <div className={styles.columns}>
         <div className={styles.canvasCol}>
-          {allowsPhoto && previewBaseImageUrl && (
+          {isAllowsPhoto && previewBaseImageUrl && (
             <MockupCanvasControl
               productImageUrl={activeProductImageUrl}
               initialDesignUrl={draft.imageUrl}

app/[locale]/products/[id]/customization-form.tsx

@@ -60,7 +60,8 @@ export function CustomizationForm({
   const config = ProductCustomizationConfig.fromJson(customizationConfig);
 
   const textErrorId = errors.text ? 'customization-text-error' : undefined;
-  const sizeErrorId = errors.size ? 'customization-size-error' : undefined;
+  const sizeErrorId =
+    errors.size == null ? undefined : 'customization-size-error';
 
   return (
     <form
@@ -96,19 +97,21 @@ export function CustomizationForm({
           </span>
           <div className={formStyles.colorCarousel}>
             {productImages.map((img) => {
-              const selected = draft.color === img.alt;
+              const isSelected = draft.color === img.alt;
               return (
                 <div
                   key={img.url}
                   role="button"
                   tabIndex={0}
-                  className={`${formStyles.colorItem} ${selected ? formStyles.colorItemSelected : ''}`}
+                  className={`${formStyles.colorItem} ${isSelected ? formStyles.colorItemSelected : ''}`}
                   onClick={() => setColor(img.alt)}
                   onKeyDown={(e) => {
-                    if (e.key === 'Enter' || e.key === ' ') {
-                      e.preventDefault();
-                      setColor(img.alt);
+                    if (!(e.key === 'Enter' || e.key === ' ')) {
+                      return;
                     }
+
+                    e.preventDefault();
+                    setColor(img.alt);
                   }}
                   title={img.alt}
                 >
@@ -131,7 +134,7 @@ export function CustomizationForm({
         <select
           value={draft.size ?? ''}
           onChange={(event) => setSize(event.target.value || null)}
-          aria-invalid={errors.size ? 'true' : undefined}
+          aria-invalid={errors.size == null ? undefined : 'true'}
           aria-describedby={sizeErrorId}
         >
           <option value="">{labels.customizationSizePlaceholder}</option>
@@ -141,7 +144,7 @@ export function CustomizationForm({
             </option>
           ))}
         </select>
-        {errors.size && (
+        {errors.size != null && (
           <p id={sizeErrorId} role="alert">
             {errors.size}
           </p>