Support loading plugin information from nested Vagrantfiles

Since plugin installation happens when the environment is first
initialized, attempt to determine the provider in use and load
any box provided Vagrantfiles to include any plugin configuration
they may include.

lib/vagrant/environment.rb

@@ -175,9 +175,7 @@ module Vagrant
       # Load any global plugins
       Vagrant::Plugin::Manager.instance.load_plugins(plugins)
 
-      if !vagrantfile.config.vagrant.plugins.empty?
-        plugins = process_configured_plugins
-      end
+      plugins = process_configured_plugins
 
       # Call the hooks that does not require configurations to be loaded
       # by using a "clean" action runner
@@ -922,6 +920,49 @@ module Vagrant
 
     protected
 
+    # Attempt to guess the configured provider in use. Will fallback
+    # to the default provider if an explicit provider name is not
+    # provided. This can be pretty error prone, but is used during
+    # initial environment setup to allow loading plugins so it doesn't
+    # need to be perfect
+    #
+    # @return [String]
+    def guess_provider
+      gp = nil
+      ARGV.each_with_index do |val, idx|
+        if val.start_with?("--provider=")
+          gp = val.split("=", 2).last
+          break
+        elsif val == "--provider"
+          gp = ARGV[idx+1]
+          break
+        end
+      end
+      return gp if gp
+      begin
+        default_provider
+      rescue Errors::NoDefaultProvider
+        # if a provider cannot be determined just return nil
+        nil
+      end
+    end
+
+    # Load any configuration provided by guests defined within
+    # the Vagrantfile to pull plugin information they may have
+    # defined.
+    def find_configured_plugins
+      plugins = []
+      provider = guess_provider
+      vagrantfile.machine_names.each do |mname|
+        ldp = @local_data_path.join("machines/#{mname}/#{provider}") if @local_data_path
+        plugins << vagrantfile.machine_config(mname, guess_provider, boxes, ldp)[:config]
+      end
+      result = plugins.reverse.inject(Vagrant::Util::HashWithIndifferentAccess.new) do |memo, val|
+        Vagrant::Util::DeepMerge.deep_merge(memo, val.vagrant.plugins)
+      end
+      Vagrant::Util::DeepMerge.deep_merge(result, vagrantfile.config.vagrant.plugins)
+    end
+
     # Check for any local plugins defined within the Vagrantfile. If
     # found, validate they are available. If they are not available,
     # request to install them, or raise an exception
@@ -939,7 +980,7 @@ module Vagrant
       # Check if defined plugins are installed
       installed = Plugin::Manager.instance.installed_plugins
       needs_install = []
-      config_plugins = vagrantfile.config.vagrant.plugins
+      config_plugins = find_configured_plugins
       config_plugins.each do |name, info|
         if !installed[name]
           needs_install << name

test/unit/vagrant/environment_test.rb

@@ -165,7 +165,7 @@ describe Vagrant::Environment do
 
         collection = double("collection")
         expect(Vagrant::BoxCollection).to receive(:new).with(
-          env.homedir.join("boxes"), anything).and_return(collection)
+          env.homedir.join("boxes"), anything).twice.and_return(collection)
         expect(collection).to receive(:upgrade_v1_1_v1_5).once
         subject
       end
@@ -761,6 +761,7 @@ VF
     before do
       m = Vagrant.plugin("2").manager
       allow(m).to receive(:providers).and_return(plugin_providers)
+      allow_any_instance_of(described_class).to receive(:process_configured_plugins)
     end
 
     it "is the highest matching usable provider" do
@@ -1431,6 +1432,108 @@ VF
     end
   end
 
+  describe "guess_provider" do
+    before { allow_any_instance_of(described_class).to receive(:process_configured_plugins) }
+
+    it "should return the default provider by default" do
+      expect(subject).to receive(:default_provider).and_return("default_provider")
+      expect(subject.send(:guess_provider)).to eq("default_provider")
+    end
+
+    context "when provider is defined via command line argument" do
+      before { stub_const("ARGV", argv) }
+
+      context "when provider is given as single argument" do
+        let(:argv) { ["--provider=single_arg"] }
+
+        it "should return the provider name" do
+          expect(subject.send(:guess_provider)).to eq("single_arg")
+        end
+      end
+
+      context "when provider is given as two arguments" do
+        let(:argv) { ["--provider", "double_arg"] }
+
+        it "should return the provider name" do
+          expect(subject.send(:guess_provider)).to eq("double_arg")
+        end
+      end
+    end
+
+    context "when no default provider is available" do
+      before {
+        expect(subject).to receive(:default_provider).
+          and_raise(Vagrant::Errors::NoDefaultProvider) }
+
+      it "should return a nil value" do
+        expect(subject.send(:guess_provider)).to be_nil
+      end
+    end
+  end
+
+  describe "#find_configured_plugins" do
+    before do
+      allow_any_instance_of(described_class).to receive(:guess_provider).and_return(:dummy)
+      allow_any_instance_of(described_class).to receive(:process_configured_plugins)
+    end
+
+    it "should find no plugins when no plugins are configured" do
+      expect(subject.send(:find_configured_plugins)).to be_empty
+    end
+
+    context "when plugins are defined in the Vagrantfile" do
+      before do
+        env.vagrantfile <<-VF
+          Vagrant.configure("2") do |config|
+            config.vagrant.plugins = "vagrant-plugin"
+          end
+          VF
+      end
+
+      it "should return the vagrant-plugin" do
+        expect(subject.send(:find_configured_plugins).keys).to include("vagrant-plugin")
+      end
+    end
+
+    context "when plugins are defined in the Vagrantfile of a box" do
+      before do
+        env.box3("foo", "1.0", :dummy, vagrantfile: <<-VF)
+          Vagrant.configure("2") do |config|
+            config.vagrant.plugins = "vagrant-plugin"
+          end
+        VF
+        env.vagrantfile <<-VF
+          Vagrant.configure("2") do |config|
+            config.vm.box = "foo"
+          end
+        VF
+      end
+
+      it "should return the vagrant-plugin" do
+        expect(subject.send(:find_configured_plugins).keys).to include("vagrant-plugin")
+      end
+    end
+
+    context "when the box does not match the provider" do
+      before do
+        env.box3("foo", "1.0", :other, vagrantfile: <<-VF)
+          Vagrant.configure("2") do |config|
+            config.vagrant.plugins = "vagrant-plugin"
+          end
+        VF
+        env.vagrantfile <<-VF
+          Vagrant.configure("2") do |config|
+            config.vm.box = "foo"
+          end
+        VF
+      end
+
+      it "should not return the vagrant-plugin" do
+        expect(subject.send(:find_configured_plugins).keys).not_to include("vagrant-plugin")
+      end
+    end
+  end
+
   describe "#process_configured_plugins" do
     let(:env) do
       isolated_environment.tap do |e|

test/unit/vagrant/util/ssh_test.rb

@@ -39,7 +39,7 @@ describe Vagrant::Util::SSH do
       dsa_authentication: true
     }}
 
-    let(:ssh_path) { "/usr/bin/ssh" }
+    let(:ssh_path) { /.*ssh/ }
 
     it "searches original PATH for executable" do
       expect(Vagrant::Util::Which).to receive(:which).with("ssh", original_path: true).and_return("valid-return")
@@ -97,8 +97,6 @@ describe Vagrant::Util::SSH do
         dsa_authentication: true
       }}
 
-      let(:ssh_path) { "/usr/bin/ssh" }
-
       it "uses the IdentityFile argument and escapes the '%' character" do
         allow(Vagrant::Util::SafeExec).to receive(:exec).and_return(nil)
         described_class.exec(ssh_info)
@@ -247,7 +245,7 @@ describe Vagrant::Util::SSH do
       it "enables ssh config loading" do
         allow(Vagrant::Util::SafeExec).to receive(:exec).and_return(nil)
         expect(Vagrant::Util::SafeExec).to receive(:exec) do |exe_path, *args|
-          expect(exe_path).to eq(ssh_path)
+          expect(exe_path).to match(ssh_path)
           config_options = ["-F", "/path/to/config"]
           expect(args & config_options).to eq(config_options)
         end