From d637b1ba49c3fd047b63765876647d0545710454 Mon Sep 17 00:00:00 2001
From: Cory Snider <cory.snider@fitbit.com>
Date: Mon, 20 Aug 2018 16:32:44 -0400
Subject: [PATCH] Normalize `null` options correctly

Fixes #227.

The first version of Node where FS functions accepted an options object
was version 0.10. Between Node 0.10 and Node 6 inclusive, all falsy
values (including the empty string) and functions are replaced with the
default options. Only truthy values which are not strings, objects or
functions throw a `TypeError`.

Node 7 introduced a breaking change: only `null`, `undefined` and
functions get replaced with the default options, and any values which
are not strings or objects throw a `TypeError`.
https://github.com/nodejs/node/pull/7165/files#diff-9a205ef7ee967ee32efee02e58b3482dR39

It is not clear which version of the Node FS API is emulated by
BrowserFS, so I have elected to implement the Node 7 behaviour.
---
 src/core/FS.ts | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/core/FS.ts b/src/core/FS.ts
index 5120e7a5..5e62a9bd 100644
--- a/src/core/FS.ts
+++ b/src/core/FS.ts
@@ -77,7 +77,8 @@ function normalizePath(p: string): string {
  * @hidden
  */
 function normalizeOptions(options: any, defEnc: string | null, defFlag: string, defMode: number | null): {encoding: string; flag: string; mode: number} {
-  switch (typeof options) {
+  // typeof null === 'object' so special-case handing is needed.
+  switch (options === null ? 'null' : typeof options) {
     case 'object':
       return {
         encoding: typeof options['encoding'] !== 'undefined' ? options['encoding'] : defEnc,
@@ -90,12 +91,16 @@ function normalizeOptions(options: any, defEnc: string | null, defFlag: string,
         flag: defFlag,
         mode: defMode!
       };
-    default:
+    case 'null':
+    case 'undefined':
+    case 'function':
       return {
         encoding: defEnc!,
         flag: defFlag,
         mode: defMode!
       };
+    default:
+      throw new TypeError(`"options" must be a string or an object, got ${typeof options} instead.`);
   }
 }