fix: check actual asset file size, not base64 encoded size

Previously we were checking whether the base64 encoded size of an asset was too large (>25Mb).
But base64 takes up more space than a normal file, so this was too aggressive.

.changeset/silly-students-live.md

@@ -0,0 +1,7 @@
+---
+"wrangler": patch
+---
+
+fix: check actual asset file size, not base64 encoded size
+
+Previously we were checking whether the base64 encoded size of an asset was too large (>25Mb). But base64 takes up more space than a normal file, so this was too aggressive.

packages/wrangler/src/__tests__/publish.test.ts

@@ -373,17 +373,24 @@ describe("publish", () => {
     });
 
     it("should error if the asset is over 25Mb", async () => {
-      const veryLargeAsset = {
-        filePath: "large-file.txt",
-        content: "X".repeat(25 * 1024 * 1024 + 1),
-      };
+      const assets = [
+        {
+          filePath: "large-file.txt",
+          // This file is greater than 25Mb when base64 encoded but small enough to be uploaded.
+          content: "X".repeat(25 * 1024 * 1024 * 0.8 + 1),
+        },
+        {
+          filePath: "too-large-file.txt",
+          content: "X".repeat(25 * 1024 * 1024 + 1),
+        },
+      ];
       const kvNamespace = {
         title: "__test-name_sites_assets",
         id: "__test-name_sites_assets-id",
       };
       writeWranglerToml("./index.js", "./assets", undefined, ["file-1.txt"]);
       writeEsmWorkerSource();
-      writeAssets("./assets", [veryLargeAsset]);
+      writeAssets("./assets", assets);
       mockUploadWorkerRequest();
       mockSubDomainRequest();
       mockListKVNamespacesRequest(kvNamespace);
@@ -395,10 +402,10 @@ describe("publish", () => {
         `"uploading assets/large-file.txt..."`
       );
       expect(stderr).toMatchInlineSnapshot(
-        `"File assets/large-file.txt is too big, it should be under 25 mb."`
+        `"File assets/too-large-file.txt is too big, it should be under 25 mb."`
       );
       expect(error).toMatchInlineSnapshot(
-        `[Error: File assets/large-file.txt is too big, it should be under 25 mb.]`
+        `[Error: File assets/too-large-file.txt is too big, it should be under 25 mb.]`
       );
     });
   });

packages/wrangler/src/sites.tsx

@@ -1,7 +1,7 @@
 import crypto from "node:crypto";
 import { createReadStream } from "node:fs";
 import * as path from "node:path";
-import { readdir, readFile } from "node:fs/promises";
+import { readdir, readFile, stat } from "node:fs/promises";
 import ignore from "ignore";
 import { fetchResult } from "./cfetch";
 import type { AssetPaths } from "./config";
@@ -127,14 +127,14 @@ export async function syncAssets(
     if (exclude(relativePath)) {
       continue;
     }
+
+    await validateAssetSize(file);
+
     const { assetKey } = await hashAsset(file);
     // now put each of the files into kv
     if (!keys.has(assetKey)) {
       console.log(`uploading ${file}...`);
       const content = await readFile(file, "base64");
-      if (content.length > 25 * 1024 * 1024) {
-        throw new Error(`File ${file} is too big, it should be under 25 mb.`);
-      }
       upload.push({
         key: assetKey,
         value: content,
@@ -158,3 +158,10 @@ function createPatternMatcher(
     return (filePath) => ignorer.test(filePath).ignored;
   }
 }
+
+async function validateAssetSize(filePath: string) {
+  const { size } = await stat(filePath);
+  if (size > 25 * 1024 * 1024) {
+    throw new Error(`File ${filePath} is too big, it should be under 25 mb.`);
+  }
+}