packer: Add description to top-level template [GH-658]

packer/template.go

@@ -16,6 +16,7 @@ import (
 // "interface{}" pointers since we actually don't know what their contents
 // are until we read the "type" field.
 type rawTemplate struct {
+	Description    string
 	Variables      map[string]interface{}
 	Builders       []map[string]interface{}
 	Hooks          map[string][]string
@@ -26,6 +27,7 @@ type rawTemplate struct {
 // The Template struct represents a parsed template, parsed into the most
 // completed form it can be without additional processing by the caller.
 type Template struct {
+	Description    string
 	Variables      map[string]RawVariable
 	Builders       map[string]RawBuilderConfig
 	Hooks          map[string][]string
@@ -115,6 +117,7 @@ func ParseTemplate(data []byte) (t *Template, err error) {
 	}
 
 	t = &Template{}
+	t.Description = rawTpl.Description
 	t.Variables = make(map[string]RawVariable)
 	t.Builders = make(map[string]RawBuilderConfig)
 	t.Hooks = rawTpl.Hooks

packer/template_test.go

@@ -111,6 +111,26 @@ func TestParseTemplate_Basic(t *testing.T) {
 	}
 }
 
+func TestParseTemplate_Description(t *testing.T) {
+	data := `
+	{
+		"description": "Foo",
+		"builders": [{"type": "something"}]
+	}
+	`
+
+	result, err := ParseTemplate([]byte(data))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if result == nil {
+		t.Fatal("should have result")
+	}
+	if result.Description != "Foo" {
+		t.Fatalf("bad: %#v", result.Description)
+	}
+}
+
 func TestParseTemplate_Invalid(t *testing.T) {
 	// Note there is an extra comma below for a purposeful
 	// syntax error in the JSON.