From a0b34488b259f8fdfb7386d2ef9f0f300c1f53e9 Mon Sep 17 00:00:00 2001
From: Gaurav Tiwari <gaurav@gauravtiwari.co.uk>
Date: Wed, 10 May 2017 19:08:53 +0100
Subject: [PATCH 1/2] Fail if yarn is outdated

---
 lib/install/bin/yarn.tt               | 2 +-
 lib/tasks/webpacker/check_yarn.rake   | 9 ++++++---
 lib/tasks/webpacker/yarn_install.rake | 2 +-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/lib/install/bin/yarn.tt b/lib/install/bin/yarn.tt
index 5187824b2..e72676245 100644
--- a/lib/install/bin/yarn.tt
+++ b/lib/install/bin/yarn.tt
@@ -2,7 +2,7 @@
 VENDOR_PATH = File.expand_path('..', __dir__)
 Dir.chdir(VENDOR_PATH) do
   begin
-    exec "yarnpkg #{ARGV.join(" ")}"
+    exec "yarn #{ARGV.join(" ")}"
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
diff --git a/lib/tasks/webpacker/check_yarn.rake b/lib/tasks/webpacker/check_yarn.rake
index a16698251..88ccced3f 100644
--- a/lib/tasks/webpacker/check_yarn.rake
+++ b/lib/tasks/webpacker/check_yarn.rake
@@ -1,11 +1,14 @@
 namespace :webpacker do
   desc "Verifies if yarn is installed"
   task :check_yarn do
+    required_yarn_version = "0.20.1"
+
     begin
-      version = `yarn --version`
-      raise Errno::ENOENT if version.blank?
+      yarn_version = `yarn --version`
+
+      raise Errno::ENOENT if yarn_version.blank? || Gem::Version.new(yarn_version) < Gem::Version.new(required_yarn_version)
     rescue Errno::ENOENT
-      puts "Webpacker requires yarn. Please download and install Yarn https://yarnpkg.com/lang/en/docs/install/"
+      puts "Webpacker requires Yarn version >= #{required_yarn_version}. Please download latest version and install https://yarnpkg.com/lang/en/docs/install/"
       puts "Exiting!" && exit!
     end
   end
diff --git a/lib/tasks/webpacker/yarn_install.rake b/lib/tasks/webpacker/yarn_install.rake
index 43e3d1431..74ef4cb31 100644
--- a/lib/tasks/webpacker/yarn_install.rake
+++ b/lib/tasks/webpacker/yarn_install.rake
@@ -1,6 +1,6 @@
 namespace :webpacker do
   desc "Support for older Rails versions.Install all JavaScript dependencies as specified via Yarn"
   task :yarn_install do
-    system("./bin/yarn")
+    exec "#{RbConfig.ruby} ./bin/yarn"
   end
 end

From 79aa0dfc5021d0b118c4e688b3f5777e8baaa448 Mon Sep 17 00:00:00 2001
From: Gaurav Tiwari <gaurav@gauravtiwari.co.uk>
Date: Thu, 11 May 2017 10:49:54 +0100
Subject: [PATCH 2/2] Revert other changes

---
 lib/install/bin/yarn.tt               | 2 +-
 lib/tasks/webpacker/yarn_install.rake | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/install/bin/yarn.tt b/lib/install/bin/yarn.tt
index e72676245..5187824b2 100644
--- a/lib/install/bin/yarn.tt
+++ b/lib/install/bin/yarn.tt
@@ -2,7 +2,7 @@
 VENDOR_PATH = File.expand_path('..', __dir__)
 Dir.chdir(VENDOR_PATH) do
   begin
-    exec "yarn #{ARGV.join(" ")}"
+    exec "yarnpkg #{ARGV.join(" ")}"
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
diff --git a/lib/tasks/webpacker/yarn_install.rake b/lib/tasks/webpacker/yarn_install.rake
index 74ef4cb31..43e3d1431 100644
--- a/lib/tasks/webpacker/yarn_install.rake
+++ b/lib/tasks/webpacker/yarn_install.rake
@@ -1,6 +1,6 @@
 namespace :webpacker do
   desc "Support for older Rails versions.Install all JavaScript dependencies as specified via Yarn"
   task :yarn_install do
-    exec "#{RbConfig.ruby} ./bin/yarn"
+    system("./bin/yarn")
   end
 end