fix(card): coerce printing Decimal prices inside cache boundary

app/(ui)/card/[slug]/page.tsx

@@ -8,7 +8,6 @@ import { OracleText } from "@/app/_components/card/oracle-text";
 import Link from "@/app/_components/link";
 import { PrintingCarousel } from "@/app/_components/builder/printing-carousel";
 import { getPrintingsForCard } from "@/lib/card/printing-queries";
-import { serializePrintings } from "@/lib/card/printing-types";
 import { getCardBySlug, getDecksContainingCard } from "@/lib/card/queries";
 import { getSession } from "@/lib/auth/session";
 
@@ -62,7 +61,7 @@ async function CardContent({ slug, from }: { slug: string; from: string | undefi
   const card = await getCardBySlug(slug);
   if (!card) notFound();
 
-  const printings = serializePrintings(await getPrintingsForCard(card.id));
+  const printings = await getPrintingsForCard(card.id);
   const back = resolveBackLink(from);
 
   const metaItems = [

app/api/cards/[id]/printings/route.ts

@@ -1,6 +1,5 @@
 import { type NextRequest, NextResponse } from "next/server";
 import { getPrintingsForCard } from "@/lib/card/printing-queries";
-import { serializePrintings } from "@/lib/card/printing-types";
 
 // Public read endpoint — printings are reference data with no per-user gating.
 // The underlying query is `'use cache'` with `cacheTag` + `cacheLife("hours")`,
@@ -17,5 +16,5 @@ export async function GET(
   }
 
   const printings = await getPrintingsForCard(cardId);
-  return NextResponse.json(serializePrintings(printings));
+  return NextResponse.json(printings);
 }

lib/card/__tests__/printing-queries.test.ts

@@ -24,10 +24,20 @@ beforeEach(() => {
 });
 
 describe("getPrintingsForCard", () => {
-  it("returns printings for the given cardId", async () => {
+  it("returns printings for the given cardId, coercing Decimal prices to number", async () => {
     const printings = [
-      { id: 10, cardId: 5, setCode: "MH3", setName: "Modern Horizons 3" },
-      { id: 9, cardId: 5, setCode: "MH2", setName: "Modern Horizons 2" },
+      {
+        id: 10,
+        cardId: 5,
+        setCode: "MH3",
+        setName: "Modern Horizons 3",
+        priceUsd: { toString: () => "12.50" }, // Prisma Decimal-like
+        priceUsdFoil: null,
+        priceUsdEtched: null,
+        priceEur: null,
+        priceEurFoil: null,
+        priceEurEtched: null,
+      },
     ];
     mockPrintingFindMany.mockResolvedValue(printings as never);
 
@@ -37,7 +47,20 @@ describe("getPrintingsForCard", () => {
       where: { cardId: 5 },
       orderBy: { id: "desc" },
     });
-    expect(result).toEqual(printings);
+    expect(result).toEqual([
+      {
+        id: 10,
+        cardId: 5,
+        setCode: "MH3",
+        setName: "Modern Horizons 3",
+        priceUsd: 12.5,
+        priceUsdFoil: null,
+        priceUsdEtched: null,
+        priceEur: null,
+        priceEurFoil: null,
+        priceEurEtched: null,
+      },
+    ]);
   });
 
   it("returns an empty array when the card has no printings", async () => {

lib/card/printing-queries.ts

@@ -1,15 +1,18 @@
 import { cacheLife, cacheTag } from "next/cache";
 import { prisma } from "@/lib/db";
+import { serializePrintings, type ClientPrinting } from "@/lib/card/printing-types";
 
 // Returns all printings for a card ordered by id desc (newest ingested first).
-// Cached aggressively — printings rarely change.
-export async function getPrintingsForCard(cardId: number) {
+// Cached aggressively — printings rarely change. Decimal price columns are coerced
+// to number *inside* the cache boundary; Prisma Decimal can't cross `'use cache'`.
+export async function getPrintingsForCard(cardId: number): Promise<ClientPrinting[]> {
   "use cache";
   cacheLife("hours");
   cacheTag(`card-printings:${cardId}`);
 
-  return prisma.printing.findMany({
+  const rows = await prisma.printing.findMany({
     where: { cardId },
     orderBy: { id: "desc" },
   });
+  return serializePrintings(rows);
 }

lib/card/printing-types.ts

@@ -1,10 +1,8 @@
-import { getPrintingsForCard } from "@/lib/card/printing-queries";
-
-type DbPrinting = Awaited<ReturnType<typeof getPrintingsForCard>>[number];
+import type { Printing } from "@/lib/generated/prisma/browser";
 
 // Client-safe shape of a Printing — Decimal columns coerced to number for serialization.
 export type ClientPrinting = Omit<
-  DbPrinting,
+  Printing,
   | "priceUsd"
   | "priceUsdFoil"
   | "priceUsdEtched"
@@ -20,7 +18,7 @@ export type ClientPrinting = Omit<
   priceEurEtched: number | null;
 };
 
-function serializePrinting(printing: DbPrinting): ClientPrinting {
+function serializePrinting(printing: Printing): ClientPrinting {
   return {
     ...printing,
     priceUsd: printing.priceUsd ? Number(printing.priceUsd) : null,
@@ -32,6 +30,6 @@ function serializePrinting(printing: DbPrinting): ClientPrinting {
   };
 }
 
-export function serializePrintings(printings: readonly DbPrinting[]): ClientPrinting[] {
+export function serializePrintings(printings: readonly Printing[]): ClientPrinting[] {
   return printings.map(serializePrinting);
 }