fix(assets): verify uploaded cosmetic size from the R2 listing

src/modules/assets/infrastructure/R2CosmeticAssetStorage.ts

@@ -18,10 +18,10 @@ export class R2CosmeticAssetStorage implements CosmeticAssetStorage {
 		});
 
 		try {
-			const persisted = await target.stat();
-			if (written !== upload.bytes.byteLength || persisted.size !== upload.bytes.byteLength) {
+			const persisted = await this.listedSize(upload.key);
+			if (written !== upload.bytes.byteLength || persisted !== upload.bytes.byteLength) {
 				throw new Error(
-					`R2 upload size mismatch for "${upload.key}": local=${upload.bytes.byteLength}, write=${written}, remote=${persisted.size}`,
+					`R2 upload size mismatch for "${upload.key}": local=${upload.bytes.byteLength}, write=${written}, remote=${persisted ?? "missing"}`,
 				);
 			}
 		} catch (error) {
@@ -30,6 +30,15 @@ export class R2CosmeticAssetStorage implements CosmeticAssetStorage {
 		}
 	}
 
+	/**
+	 * Reads the stored size from a listing. `stat()` reported 0 bytes for a small
+	 * JSON object that the listing showed was stored in full.
+	 */
+	private async listedSize(key: string): Promise<number | undefined> {
+		const listed = await this.client.list({ prefix: key });
+		return listed.contents?.find((object) => object.key === key)?.size;
+	}
+
 	async delete(key: string): Promise<void> {
 		await this.client.delete(key);
 	}

tests/unit/modules/assets/infrastructure/R2CosmeticAssetStorage.test.ts

@@ -0,0 +1,67 @@
+import type { S3Client } from "bun";
+import { describe, expect, it, mock } from "bun:test";
+
+import { R2CosmeticAssetStorage } from "../../../../../src/modules/assets/infrastructure/R2CosmeticAssetStorage";
+
+interface FakeR2 {
+	exists?: boolean;
+	written?: number;
+	statSize?: number;
+	listedSize?: number;
+}
+
+function fakeClient({ exists = false, written, statSize = 0, listedSize }: FakeR2) {
+	const deleteObject = mock(async (_key: string) => undefined);
+	const client = {
+		file: (key: string) => ({
+			exists: async () => exists,
+			stat: async () => ({ size: statSize }),
+			delete: () => deleteObject(key),
+		}),
+		write: async (_key: string, bytes: Uint8Array) => written ?? bytes.byteLength,
+		list: async ({ prefix }: { prefix: string }) => ({
+			contents: listedSize === undefined ? [] : [{ key: prefix, size: listedSize }],
+		}),
+		delete: (key: string) => deleteObject(key),
+	};
+	return { client: client as unknown as S3Client, deleteObject };
+}
+
+const upload = {
+	key: "emote-packs/halloween-duelist/pack.json",
+	bytes: new Uint8Array(538),
+	contentType: "application/json",
+};
+
+describe("R2CosmeticAssetStorage.put", () => {
+	it("accepts an upload whose listed size matches even when stat reports 0 bytes", async () => {
+		const { client, deleteObject } = fakeClient({ statSize: 0, listedSize: 538 });
+
+		await new R2CosmeticAssetStorage(client).put(upload);
+
+		expect(deleteObject).not.toHaveBeenCalled();
+	});
+
+	it("rejects and deletes an upload whose listed size differs", async () => {
+		const { client, deleteObject } = fakeClient({ listedSize: 0 });
+
+		await expect(new R2CosmeticAssetStorage(client).put(upload)).rejects.toThrow(
+			'R2 upload size mismatch for "emote-packs/halloween-duelist/pack.json": local=538, write=538, remote=0',
+		);
+		expect(deleteObject).toHaveBeenCalledWith(upload.key);
+	});
+
+	it("rejects and deletes an upload that is missing from the listing", async () => {
+		const { client, deleteObject } = fakeClient({});
+
+		await expect(new R2CosmeticAssetStorage(client).put(upload)).rejects.toThrow("remote=missing");
+		expect(deleteObject).toHaveBeenCalledWith(upload.key);
+	});
+
+	it("rejects and deletes an upload whose write count differs", async () => {
+		const { client, deleteObject } = fakeClient({ written: 10, listedSize: 538 });
+
+		await expect(new R2CosmeticAssetStorage(client).put(upload)).rejects.toThrow("write=10");
+		expect(deleteObject).toHaveBeenCalledWith(upload.key);
+	});
+});