fix: Disable base64 optimization in ReactNative (#3564)

Our base64 encoding optimization does not run in React Native, because
React Native doesn't support creating Files/Blobs from buffers.

---------

Co-authored-by: Maarten Zuidhoorn <[email protected]>

Author: FrederikBolding

packages/snaps-utils/src/base64.test.ts

@@ -51,6 +51,21 @@ describe('encodeBase64', () => {
     );
     expect(await encodeBase64(vfile)).toBe('eyJmb28iOiJiYXIifQ==');
   });
+
+  it('does not use optimization when running in React Native', async () => {
+    Object.defineProperty(globalThis, 'FileReader', {
+      value: MockFileReader,
+    });
+
+    Object.defineProperty(globalThis, 'navigator', {
+      value: { product: 'ReactNative' },
+    });
+
+    const vfile = new VirtualFile(
+      stringToBytes(JSON.stringify({ foo: 'bar' })),
+    );
+    expect(await encodeBase64(vfile)).toBe('eyJmb28iOiJiYXIifQ==');
+  });
 });
 
 describe('decodeBase64', () => {

packages/snaps-utils/src/base64.ts

@@ -11,8 +11,10 @@ import type { VirtualFile } from './virtual-file';
  */
 export async function encodeBase64(input: Uint8Array | VirtualFile | string) {
   const bytes = getBytes(input);
-  // In the browser, FileReader is much faster than bytesToBase64.
-  if ('FileReader' in globalThis) {
+  const isReactNative =
+    typeof navigator !== 'undefined' && navigator.product === 'ReactNative';
+  // In the browser, FileReader is much faster than bytesToBase64. This is not supported in React Native however.
+  if ('FileReader' in globalThis && !isReactNative) {
     return await new Promise((resolve, reject) => {
       const reader = Object.assign(new FileReader(), {
         onload: () =>