fix: test before using Buffers

[ST-DDT]

Fixes #3285

---

Adds a feature check before committing to use the Buffer methods.

Alternative

Remove the Buffer "shortcut" check and usage from the base64url method.

[netlify]

✅ Deploy Preview for fakerjs ready!

Name	Link
🔨 Latest commit	e1b0b4b
🔍 Latest deploy log	https://app.netlify.com/sites/fakerjs/deploys/67ad147ba0bf67000878322f
😎 Deploy Preview	https://deploy-preview-3400.fakerjs.dev
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 99.97%. Comparing base (7c749b6) to head (e1b0b4b).

Files with missing lines	Patch %	Lines
src/internal/base64.ts	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #3400      +/-   ##
==========================================
- Coverage   99.97%   99.97%   -0.01%     
==========================================
  Files        2811     2811              
  Lines      216965   216972       +7     
  Branches      941      941              
==========================================
+ Hits       216914   216919       +5     
- Misses         51       53       +2     

Files with missing lines	Coverage Δ
src/internal/base64.ts	44.00% <77.77%> (+10.66%)	⬆️

[xDivisionByZerox]

I'm honestly fine with both solutions. Having the explicit check function with documentation linking to the related upstream issues, might remind someone in the future to look into this and remove the workaround. On the other side, most of us are propably suvscribed to the external issues as well and will get notified anyway.

[Shinigami92]

My opinionated solution:

/* eslint-disable no-undef -- This file serves as a compatibility layer between environments */

/**
 * Checks whether the environment supports the given encoding on the `Buffer` class.
 * This is required because some `Buffer` polyfills do not support all encodings.
 *
 * @param encoding The encoding to check.
 *
 * @see https://www.npmjs.com/package/buffer
 * @see https://github.com/feross/buffer/issues/309
 */
function bufferFeatureCheck(encoding: BufferEncoding): boolean {
  try {
    return typeof Buffer.from("test").toString(encoding) === "string";
  } catch {
    return false;
  }
}

const SUPPORTS_BASE64_BUFFER =
  typeof Buffer === "undefined" || !bufferFeatureCheck("base64");
const SUPPORTS_BASE64_URL_BUFFER =
  typeof Buffer === "undefined" || !bufferFeatureCheck("base64url");

/**
 * This works the same as `Buffer.from(input).toString('base64')`
 * to work on both Node.js and browser environment.
 *
 * @internal
 *
 * @param input The string to encode to Base64.
 *
 * @returns Base64 encoded string.
 *
 * @see https://datatracker.ietf.org/doc/html/rfc4648
 *
 * @example const encodedHeader = toBase64(JSON.stringify(header));
 */
export function toBase64(input: string): string {
  if (SUPPORTS_BASE64_BUFFER) {
    return Buffer.from(input).toString("base64");
  }

  const utf8Bytes = new TextEncoder().encode(input);
  const binaryString = Array.from(utf8Bytes, (byte) =>
    String.fromCodePoint(byte)
  ).join("");
  return btoa(binaryString);
}

/**
 * This works the same as `Buffer.from(input).toString('base64url')`
 * to work on both Node.js and browser environment.
 *
 * @internal
 *
 * @param input The string to encode to Base64 URL.
 *
 * @returns Base64 URL encoded string.
 *
 * @see https://datatracker.ietf.org/doc/html/rfc4648
 *
 * @example const encodedHeader = toBase64Url(JSON.stringify(header));
 */
export function toBase64Url(input: string): string {
  if (SUPPORTS_BASE64_URL_BUFFER) {
    return Buffer.from(input).toString("base64url");
  }

  return toBase64(input)
    .replaceAll("+", "-")
    .replaceAll("/", "_")
    .replaceAll(/=+$/g, "");
}

I know this moves the check into the function, but makes it (to me) much more readable. I don't think that the condition has a to bad performance compared to actually craft the base64 string.

Edit: we might even be able to remove the typeof Buffer === "undefined", because the try-catch would catch it anyway 😅