(#9622) Use SafeExec for docker-exec

This commit uses the internal helper SafeExec rather than using the
Kernel class directly. It also adds a test to ensure that if the `-t`
option is used, it will call SafeExec.

plugins/providers/docker/command/exec.rb

@@ -1,3 +1,5 @@
+require 'vagrant/util/safe_exec'
+
 module VagrantPlugins
   module DockerProvider
     module Command
@@ -86,7 +88,7 @@ module VagrantPlugins
           exec_options = options
 
           if options[:pty]
-            Kernel.system(*exec_cmd)
+            Vagrant::Util::SafeExec.exec(exec_cmd[0], *exec_cmd[1..-1])
           else
             output = ""
             machine.provider.driver.execute(*exec_cmd, exec_options) do |type, data|

test/unit/plugins/providers/docker/command/exec_test.rb

@@ -5,14 +5,30 @@ describe VagrantPlugins::DockerProvider::Command::Exec do
   include_context "unit"
   include_context "command plugin helpers"
 
-  let(:sandbox) do
-    isolated_environment
+  let(:env) { {
+    action_runner: action_runner,
+    machine: machine,
+    ui: Vagrant::UI::Silent.new,
+  } }
+
+  subject { described_class.new(app, env) }
+  let(:argv) { [] }
+
+  let(:iso_env) do
+    # We have to create a Vagrantfile so there is a root path
+    isolated_environment.tap do |env|
+      env.vagrantfile("")
+    end
   end
 
-  let(:argv) { [] }
-  let(:env) { sandbox.create_vagrant_env }
+  let(:iso_vagrant_env) { iso_env.create_vagrant_env }
 
-  let(:vagrantfile_path) { File.join(env.cwd, "Vagrantfile") }
+  let(:action_runner) { double("action_runner") }
+  let(:box) do
+    box_dir = iso_env.box3("foo", "1.0", :virtualbox)
+    Vagrant::Box.new("foo", :virtualbox, "1.0", box_dir)
+  end
+  let(:machine) { iso_vagrant_env.machine(iso_vagrant_env.machine_names[0], :dummy) }
 
   subject { described_class.new(argv, env) }
 
@@ -23,14 +39,19 @@ describe VagrantPlugins::DockerProvider::Command::Exec do
 
   before do
     allow(Vagrant.plugin("2").manager).to receive(:commands).and_return({})
-    allow(subject).to receive(:exec_command)
   end
 
-  after do
-    sandbox.close
-  end
+  describe "#exec_command" do
+    describe "with -t option" do
+      let(:command) { ["/bin/bash"] }
+      let(:options) { {pty: "true"} }
 
-  describe "#execute" do
+      it "calls Safe Exec" do
+        allow(Kernel).to receive(:exec).and_return(true)
+        expect(Vagrant::Util::SafeExec).to receive(:exec).with("docker", "exec", "-t", anything, "/bin/bash")
+        subject.exec_command(machine, command, options)
+      end
+    end
     describe "without a command" do
       let(:argv) { [] }