fix: Correct file name in web-ext submit in Node 24

src/util/submit-addon.js

@@ -14,29 +14,6 @@ const log = createLogger(import.meta.url);
 
 export const defaultAsyncFsReadFile = fsPromises.readFile;
 
-// Used by fileFromSync method to make sure the form-data entry will
-// include a filename derived from the file path.
-//
-// TODO: Get rid of this hack when we will bump the web-ext nodejs
-// version required to nodejs v20 (where the native File constructor
-// exists).
-export class FileBlob extends Blob {
-  #name = '';
-
-  constructor(fileBits, fileName, options) {
-    super(fileBits, options);
-    this.#name = String(fileName);
-  }
-
-  get name() {
-    return this.#name;
-  }
-
-  get [Symbol.toStringTag]() {
-    return 'File';
-  }
-}
-
 export class JwtApiAuth {
   #apiKey;
   #apiSecret;
@@ -116,7 +93,21 @@ export default class Client {
     // submitted and fail with the error message:
     // "Unsupported file type, please upload a supported file (.crx, .xpi, .zip)."
     const fileData = readFileSync(filePath);
-    return new FileBlob([fileData], basename(filePath));
+    // eslint-disable-next-line no-shadow -- File is in Node v20.0.0+.
+    let File = global.File;
+    // TODO: Use the File global directly without the fallback when we drop
+    // support for Node versions before v20.
+    if (typeof File === 'undefined') {
+      // Even without File being public, its interface and constructor could
+      // be accessed indirectly from the FormData interface. According to the
+      // FormData spec (that Node.js implements, via undici), the entry value
+      // of a FormData is always a scalar value or a File:
+      // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#form-entry-value
+      const fd = new FormData();
+      fd.set('x', new Blob([]));
+      File = fd.get('x').constructor;
+    }
+    return new File([fileData], basename(filePath));
   }
 
   nodeFetch(url, { method, headers, body, agent }) {

tests/unit/test-util/test.submit-addon.js

@@ -1,6 +1,12 @@
 import { createHash } from 'crypto';
 import { promises as fsPromises, readFileSync } from 'fs';
 import path from 'path';
+// eslint-disable-next-line no-shadow -- TODO: Remove when we require Node v20+.
+import { File } from 'node:buffer';
+// ^ note: this was introduced in v18.13.0. Because of its unavailability in
+// earlier versions, the actual implementation in submit-addon.js retrieves
+// the File constructor in a different way, which also works in Node 18.0.0.
+// Our CI tests with Node 18.19.0 as the lowest version, so this passes tests.
 
 // eslint-disable-next-line import/no-extraneous-dependencies
 import CRC32 from 'crc-32';
@@ -16,9 +22,6 @@ import Client, {
   saveIdToFile,
   saveUploadUuidToFile,
   signAddon,
-
-  // eslint-disable-next-line no-shadow -- Not actually available under Node 20. Use global once possible.
-  FileBlob as File,
 } from '../../../src/util/submit-addon.js';
 import { withTempDir } from '../../../src/util/temp-dir.js';
 
@@ -372,6 +375,25 @@ describe('util.submit-addon', () => {
           assert.equal(await fileRes.text(), FILE_CONTENT);
           assert.equal(String(fileRes), '[object File]');
         }));
+
+      it('should return a File whose name is preserved in FormData', () =>
+        withTempDir(async (tmpDir) => {
+          const client = new Client(clientDefaults);
+          const FILE_BASENAME = 'testfile.txt';
+          const FILE_CONTENT = 'somecontent';
+          const filePath = path.join(tmpDir.path(), FILE_BASENAME);
+          await fsPromises.writeFile(filePath, FILE_CONTENT);
+          const fileRes = client.fileFromSync(filePath);
+
+          // Regression test for https://github.com/mozilla/web-ext/issues/3418
+          const fd = new FormData();
+          fd.set('upload', fileRes);
+          const fileOut = fd.get('upload');
+
+          assert.equal(fileOut.name, FILE_BASENAME);
+          assert.equal(fileOut.size, FILE_CONTENT.length);
+          assert.equal(await fileOut.text(), FILE_CONTENT);
+        }));
     });
 
     describe('getPreviousUuidOrUploadXpi', () => {