From eb24e2fddc57313027a8281f9ced6fc169252cd9 Mon Sep 17 00:00:00 2001
From: Chunpeng Huo <huocp@me.com>
Date: Fri, 14 Aug 2020 09:38:58 +1000
Subject: [PATCH] fix: synchronize patching binding/createWriteStream/cwd/chdir

All the patches now check same realBinding._mockedBinding. This should
fix the edge cases around the new feature bypass().

follows up #306
---
 lib/index.js | 92 +++++++++++++++++++---------------------------------
 1 file changed, 34 insertions(+), 58 deletions(-)

diff --git a/lib/index.js b/lib/index.js
index 2f6b5ac6..efe047db 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -3,21 +3,39 @@
 const Binding = require('./binding');
 const FSError = require('./error');
 const FileSystem = require('./filesystem');
-const realBinding = process.binding('fs');
 const path = require('path');
 const loader = require('./loader');
 const bypass = require('./bypass');
 const fs = require('fs');
 
+const realBinding = process.binding('fs');
 const toNamespacedPath = FileSystem.toNamespacedPath;
+const realCreateWriteStream = fs.createWriteStream;
+const realCwd = process.cwd;
+const realChdir = process.chdir;
 
-const realProcessProps = {
-  cwd: process.cwd,
-  chdir: process.chdir
+let mockedCwd; // To be set in mockfs()
+process.cwd = function() {
+  if (realBinding._mockedBinding) {
+    return mockedCwd;
+  }
+  return realCwd();
+};
+
+process.chdir = function(directory) {
+  if (realBinding._mockedBinding) {
+    if (
+      !realBinding._mockedBinding
+        .stat(toNamespacedPath(directory))
+        .isDirectory()
+    ) {
+      throw new FSError('ENOTDIR');
+    }
+    mockedCwd = path.resolve(mockedCwd, directory);
+  } else {
+    return realChdir();
+  }
 };
-const realCreateWriteStream = fs.createWriteStream;
-const realStats = realBinding.Stats;
-const realStatWatcher = realBinding.StatWatcher;
 
 /**
  * Pre-patch fs binding.
@@ -50,15 +68,6 @@ for (const key in Binding.prototype) {
   }
 }
 
-function overrideBinding(binding) {
-  realBinding._mockedBinding = binding;
-}
-
-function overrideProcess(cwd, chdir) {
-  process.cwd = cwd;
-  process.chdir = chdir;
-}
-
 /**
  * Have to disable write stream _writev on nodejs v10+.
  *
@@ -83,30 +92,14 @@ function overrideProcess(cwd, chdir) {
  * Luckily _writev is an optional method on Writeable stream implementation.
  * When _writev is missing, it will fall back to make multiple _write calls.
  */
-function overrideCreateWriteStream() {
-  fs.createWriteStream = function(path, options) {
-    const output = realCreateWriteStream(path, options);
-    // disable _writev, this will over shadow WriteStream.prototype._writev
+fs.createWriteStream = function(path, options) {
+  const output = realCreateWriteStream(path, options);
+  // disable _writev, this will over shadow WriteStream.prototype._writev
+  if (realBinding._mockedBinding) {
     output._writev = undefined;
-    return output;
-  };
-}
-
-function restoreBinding() {
-  delete realBinding._mockedBinding;
-  realBinding.Stats = realStats;
-  realBinding.StatWatcher = realStatWatcher;
-}
-
-function restoreProcess() {
-  for (const key in realProcessProps) {
-    process[key] = realProcessProps[key];
   }
-}
-
-function restoreCreateWriteStream() {
-  fs.createWriteStream = realCreateWriteStream;
-}
+  return output;
+};
 
 /**
  * Swap out the fs bindings for a mock file system.
@@ -120,23 +113,8 @@ function restoreCreateWriteStream() {
 exports = module.exports = function mock(config, options) {
   const system = FileSystem.create(config, options);
   const binding = new Binding(system);
-
-  overrideBinding(binding);
-
-  let currentPath = process.cwd();
-  overrideProcess(
-    function cwd() {
-      return currentPath;
-    },
-    function chdir(directory) {
-      if (!binding.stat(toNamespacedPath(directory)).isDirectory()) {
-        throw new FSError('ENOTDIR');
-      }
-      currentPath = path.resolve(currentPath, directory);
-    }
-  );
-
-  overrideCreateWriteStream();
+  mockedCwd = realCwd();
+  realBinding._mockedBinding = binding;
 };
 
 /**
@@ -155,9 +133,7 @@ exports.getMockRoot = function() {
  * Restore the fs bindings for the real file system.
  */
 exports.restore = function() {
-  restoreBinding();
-  restoreProcess();
-  restoreCreateWriteStream();
+  delete realBinding._mockedBinding;
 };
 
 /**