Add faster alternative for checking mjml version

lib/mjml.rb

@@ -48,6 +48,7 @@ def self.run_mjml(args, mjml_bin: valid_mjml_binary)
   def self.valid_mjml_binary
     self.valid_mjml_binary = @@valid_mjml_binary ||
                              check_for_custom_mjml_binary ||
+                             check_for_node_modules_mjml_binary ||
                              check_for_package_mjml_binary ||
                              check_for_global_mjml_binary ||
                              check_for_mrml_binary
@@ -73,6 +74,15 @@ def self.check_for_custom_mjml_binary
           'it is a valid MJML binary. Please check your configuration.'
   end
 
+  def self.check_for_node_modules_mjml_binary
+    package_json = JSON.parse(Rails.root.join('node_modules/mjml/package.json').read)
+    if package_json['version'].start_with?(Mjml.mjml_binary_version_supported)
+      Rails.root.join('node_modules/.bin/mjml').to_s
+    end
+  rescue StandardError
+    false
+  end
+
   def self.check_for_mjml_package(package_manager, bin_command, binary_path)
     stdout, _, status = Open3.capture3("which #{package_manager}")
     return unless status.success?

test/mjml_test.rb

@@ -159,6 +159,15 @@ class NotifierMailerTest < ActiveSupport::TestCase
                                      'but MJML-Rails could not validate that it is a valid MJML binary'))
     end
 
+    it 'checks for node_modules first to avoid running the binary' do
+      Rails.stubs(:root).returns(Pathname.new('.'))
+      Mjml.stubs(:check_for_package_mjml_binary).never
+      Mjml.stubs(:check_for_global_mjml_binary).never
+      Mjml.stubs(:check_for_mrml_binary).never
+
+      expect(Mjml.valid_mjml_binary.to_s).must_match(%r{node_modules/.bin/mjml})
+    end
+
     it 'can use MRML and check for a valid binary' do
       Mjml.use_mrml = true
       Mjml.stubs(:check_for_custom_mjml_binary).returns(false)