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🏁 Preserve file extension when extracting from asar

Currently, when calling `copyFileOut`, the original extension from the
file is lost, and a generic `*.tmp` is added instead.

This becomes problematic in the scenario where we use
`child_process.execFile` on a Windows Batch script that lives inside the
`asar` package.

Windows relies on the extension being present in order to interpret the
script accordingly, which results in the following bug because the
operating system doesn't know what do to with this `*.tmp` file:

Error: spawn UNKNOWN

Steps to reproduce:

1. Create a dummy batch script (test.bat):

@echo off
echo "Hello world"

2. Create an electron app that attemps to call this script with

var child_process = require('child_process');
var path = require('path');

child_process.execFile(path.join(__dirname, 'test.bat'), function(error, stdout) {
    if (error) throw error;

3. Package this small application as an asar archive:

> asar pack mytestapp app.asar

4. Execute the application:

> electron.exe app.asar
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Juan Cruz Viotti
Juan Cruz Viotti committed Dec 1, 2015
1 parent 85b7aa6 commit a99c193cf2d783308a0777e6c6ee606590bfa263
@@ -272,7 +272,8 @@ bool Archive::CopyFileOut(const base::FilePath& path, base::FilePath* out) {

scoped_ptr<ScopedTemporaryFile> temp_file(new ScopedTemporaryFile);
if (!temp_file->InitFromFile(&file_, info.offset, info.size))
base::FilePath::StringType ext = path.Extension();
if (!temp_file->InitFromFile(&file_, ext, info.offset, info.size))
return false;

#if defined(OS_POSIX)
@@ -28,20 +28,28 @@ ScopedTemporaryFile::~ScopedTemporaryFile() {

bool ScopedTemporaryFile::Init() {
bool ScopedTemporaryFile::Init(const base::FilePath::StringType ext) {
if (!path_.empty())
return true;

base::ThreadRestrictions::ScopedAllowIO allow_io;
return base::CreateTemporaryFile(&path_);

base::FilePath temporaryPath_;
if (!base::CreateTemporaryFile(&temporaryPath_)) {
return false;

path_ = temporaryPath_.AddExtension(ext);
return base::Move(temporaryPath_, path_);

bool ScopedTemporaryFile::InitFromFile(base::File* src,
const base::FilePath::StringType ext,
uint64 offset, uint64 size) {
if (!src->IsValid())
return false;

if (!Init())
if (!Init(ext))
return false;

std::vector<char> buf(size);
@@ -22,11 +22,13 @@ class ScopedTemporaryFile {
virtual ~ScopedTemporaryFile();

// Init an empty temporary file.
bool Init();
// Init an empty temporary file with a certain extension.
bool Init(const base::FilePath::StringType ext);

// Init an temporary file and fill it with content of |path|.
bool InitFromFile(base::File* src, uint64 offset, uint64 size);
bool InitFromFile(base::File* src,
const base::FilePath::StringType ext,
uint64 offset, uint64 size);

base::FilePath path() const { return path_; }

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