Expose default vagrantfile template as a template variable {{.DefaultTemplate}}

.web-docs/components/builder/vagrant/README.md

@@ -101,6 +101,8 @@ the Compress post-processor will not work with this builder.
   be found here. The template variables available to you are
   `{{ .BoxName }}`, `{{ .SyncedFolder }}`, and `{{.InsertKey}}`, which
   correspond to the Packer options box_name, synced_folder, and insert_key.
+  Alternatively, the template variable `{{.DefaultTemplate}}` is available for
+  use if you wish to extend the default generated template.
 
 - `synced_folder` (string) - Path to the folder to be synced to the guest. The path can be absolute
   or relative to the directory Packer is being run from.

builder/vagrant/builder.go

@@ -105,6 +105,8 @@ type Config struct {
 	// be found here. The template variables available to you are
 	// `{{ .BoxName }}`, `{{ .SyncedFolder }}`, and `{{.InsertKey}}`, which
 	// correspond to the Packer options box_name, synced_folder, and insert_key.
+	// Alternatively, the template variable `{{.DefaultTemplate}}` is available for
+	// use if you wish to extend the default generated template.
 	Template string `mapstructure:"template" required:"false"`
 	// Path to the folder to be synced to the guest. The path can be absolute
 	// or relative to the directory Packer is being run from.

builder/vagrant/step_create_vagrantfile.go

@@ -6,26 +6,37 @@ package vagrant
 import (
 	"context"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
+	"strings"
 	"text/template"
 
 	"github.com/hashicorp/packer-plugin-sdk/multistep"
 	packersdk "github.com/hashicorp/packer-plugin-sdk/packer"
 )
 
 type StepCreateVagrantfile struct {
-	Template     string
-	OutputDir    string
-	SyncedFolder string
-	GlobalID     string
-	SourceBox    string
-	BoxName      string
-	InsertKey    bool
+	Template               string
+	OutputDir              string
+	SyncedFolder           string
+	GlobalID               string
+	SourceBox              string
+	BoxName                string
+	InsertKey              bool
+	defaultTemplateContent string
 }
 
-var DEFAULT_TEMPLATE = `Vagrant.configure("2") do |config|
+type VagrantfileOptions struct {
+	SyncedFolder    string
+	SourceBox       string
+	BoxName         string
+	InsertKey       bool
+	DefaultTemplate string
+}
+
+const DEFAULT_TEMPLATE = `Vagrant.configure("2") do |config|
   config.vm.define "source", autostart: false do |source|
 	source.vm.box = "{{.SourceBox}}"
 	config.ssh.insert_key = {{.InsertKey}}
@@ -42,51 +53,55 @@ var DEFAULT_TEMPLATE = `Vagrant.configure("2") do |config|
   {{- end}}
 end`
 
-type VagrantfileOptions struct {
-	SyncedFolder string
-	SourceBox    string
-	BoxName      string
-	InsertKey    bool
-}
+var defaultTemplate = template.Must(template.New("VagrantTpl").Parse(DEFAULT_TEMPLATE))
+
+func (s *StepCreateVagrantfile) createVagrantfile() (tplPath string, err error) {
+	tplPath, err = filepath.Abs(filepath.Join(s.OutputDir, "Vagrantfile"))
+	if err != nil {
+		return
+	}
 
-func (s *StepCreateVagrantfile) createVagrantfile() (string, error) {
-	tplPath := filepath.Join(s.OutputDir, "Vagrantfile")
 	templateFile, err := os.Create(tplPath)
 	if err != nil {
-		retErr := fmt.Errorf("Error creating vagrantfile %s", err.Error())
-		return "", retErr
+		err = fmt.Errorf("Error creating vagrantfile %s", err.Error())
+		return
+	}
+
+	if s.defaultTemplateContent, err = s.renderDefaultTemplate(); err != nil {
+		return
 	}
 
-	var tpl *template.Template
 	if s.Template == "" {
-		// Generate vagrantfile template based on our default
-		tpl = template.Must(template.New("VagrantTpl").Parse(DEFAULT_TEMPLATE))
+		// Generate vagrantfile template based on our default template
+		_, err = templateFile.WriteString(s.defaultTemplateContent)
 	} else {
-		// Read in the template from provided file.
+		// Otherwise, read in the template from provided file.
+		var tpl *template.Template
 		tpl, err = template.ParseFiles(s.Template)
-		if err != nil {
-			return "", err
+		if err == nil {
+			err = s.executeTemplate(tpl, templateFile)
 		}
 	}
+	return
+}
 
+func (s *StepCreateVagrantfile) executeTemplate(tpl *template.Template, file io.Writer) error {
 	opts := &VagrantfileOptions{
-		SyncedFolder: s.SyncedFolder,
-		BoxName:      s.BoxName,
-		SourceBox:    s.SourceBox,
-		InsertKey:    s.InsertKey,
-	}
-
-	err = tpl.Execute(templateFile, opts)
-	if err != nil {
-		return "", err
+		SyncedFolder:    s.SyncedFolder,
+		BoxName:         s.BoxName,
+		SourceBox:       s.SourceBox,
+		InsertKey:       s.InsertKey,
+		DefaultTemplate: s.defaultTemplateContent,
 	}
+	return tpl.Execute(file, opts)
+}
 
-	abspath, err := filepath.Abs(tplPath)
-	if err != nil {
-		return "", err
+func (s *StepCreateVagrantfile) renderDefaultTemplate() (string, error) {
+	buf := new(strings.Builder)
+	if err := s.executeTemplate(defaultTemplate, buf); err != nil {
+		return "", fmt.Errorf("Error rendering default template %w", err)
 	}
-
-	return abspath, nil
+	return buf.String(), nil
 }
 
 func (s *StepCreateVagrantfile) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction {

builder/vagrant/step_create_vagrantfile_test.go

@@ -6,6 +6,7 @@ package vagrant
 import (
 	"io/ioutil"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -116,3 +117,62 @@ end`
 		t.Fatalf("EXPECTED: \n%s\n\n RECEIVED: \n%s\n\n", expected, actual)
 	}
 }
+
+func TestCreateFile_customTemplate(t *testing.T) {
+	workdir := t.TempDir()
+	vagrantfileTemplatePath := filepath.Join(workdir, "Vagrantfile.tpl")
+	f, err := os.Create(vagrantfileTemplatePath)
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+	defer f.Close()
+
+	var TEMPLATE = `{{ .DefaultTemplate }}
+Vagrant.configure("2") do |config|
+  config.vm.provider "virtualbox" do |vb|
+    vb.customize ['modifyvm', :id, '--nested-hw-virt', 'on']
+  end
+end`
+
+	_, err = f.WriteString(TEMPLATE)
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	testy := StepCreateVagrantfile{
+		OutputDir: "./",
+		SourceBox: "apples",
+		BoxName:   "bananas",
+		Template:  vagrantfileTemplatePath,
+	}
+	templatePath, err := testy.createVagrantfile()
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	defer os.Remove(templatePath)
+	contents, err := ioutil.ReadFile(templatePath)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	actual := string(contents)
+	expected := `Vagrant.configure("2") do |config|
+  config.vm.define "source", autostart: false do |source|
+	source.vm.box = "apples"
+	config.ssh.insert_key = false
+  end
+  config.vm.define "output" do |output|
+	output.vm.box = "bananas"
+	output.vm.box_url = "file://package.box"
+	config.ssh.insert_key = false
+  end
+  config.vm.synced_folder ".", "/vagrant", disabled: true
+end
+Vagrant.configure("2") do |config|
+  config.vm.provider "virtualbox" do |vb|
+    vb.customize ['modifyvm', :id, '--nested-hw-virt', 'on']
+  end
+end`
+	if ok := strings.Compare(actual, expected); ok != 0 {
+		t.Fatalf("EXPECTED: \n%s\n\n RECEIVED: \n%s\n\n", expected, actual)
+	}
+}

docs-partials/builder/vagrant/Config-not-required.mdx

@@ -48,6 +48,8 @@
   be found here. The template variables available to you are
   `{{ .BoxName }}`, `{{ .SyncedFolder }}`, and `{{.InsertKey}}`, which
   correspond to the Packer options box_name, synced_folder, and insert_key.
+  Alternatively, the template variable `{{.DefaultTemplate}}` is available for
+  use if you wish to extend the default generated template.
 
 - `synced_folder` (string) - Path to the folder to be synced to the guest. The path can be absolute
   or relative to the directory Packer is being run from.