command/fix: validate resulting template [GH-2075]

command/fix.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/mitchellh/packer/fix"
+	"github.com/mitchellh/packer/template"
 )
 
 type FixCommand struct {
@@ -16,7 +17,9 @@ type FixCommand struct {
 }
 
 func (c *FixCommand) Run(args []string) int {
+	var flagValidate bool
 	flags := c.Meta.FlagSet("fix", FlagSetNone)
+	flags.BoolVar(&flagValidate, "validate", true, "")
 	flags.Usage = func() { c.Ui.Say(c.Help()) }
 	if err := flags.Parse(args); err != nil {
 		return 1
@@ -80,6 +83,28 @@ func (c *FixCommand) Run(args []string) int {
 	result = strings.Replace(result, `\u003c`, "<", -1)
 	result = strings.Replace(result, `\u003e`, ">", -1)
 	c.Ui.Say(result)
+
+	if flagValidate {
+		// Attemot to parse and validate the template
+		tpl, err := template.Parse(strings.NewReader(result))
+		if err != nil {
+			c.Ui.Error(fmt.Sprintf(
+				"Error! Fixed template fails to parse: %s\n\n"+
+					"This is usually caused by an error in the input template.\n"+
+					"Please fix the error and try again.",
+				err))
+			return 1
+		}
+		if err := tpl.Validate(); err != nil {
+			c.Ui.Error(fmt.Sprintf(
+				"Error! Fixed template failed to validate: %s\n\n"+
+					"This is usually caused by an error in the input template.\n"+
+					"Please fix the error and try again.",
+				err))
+			return 1
+		}
+	}
+
 	return 0
 }
 
@@ -102,6 +127,10 @@ Fixes that are run:
   pp-vagrant-override Replaces old-style provider overrides for the Vagrant
                       post-processor to new-style as of Packer 0.5.0.
   virtualbox-rename   Updates "virtualbox" builders to "virtualbox-iso"
+
+Options:
+
+  -validate=true      If true (default), validates the fixed template.
 `
 
 	return strings.TrimSpace(helpText)

command/fix_test.go

@@ -0,0 +1,58 @@
+package command
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestFix_noArgs(t *testing.T) {
+	c := &PushCommand{Meta: testMeta(t)}
+	code := c.Run(nil)
+	if code != 1 {
+		t.Fatalf("bad: %#v", code)
+	}
+}
+
+func TestFix_multiArgs(t *testing.T) {
+	c := &PushCommand{Meta: testMeta(t)}
+	code := c.Run([]string{"one", "two"})
+	if code != 1 {
+		t.Fatalf("bad: %#v", code)
+	}
+}
+
+func TestFix(t *testing.T) {
+	c := &FixCommand{
+		Meta: testMeta(t),
+	}
+
+	args := []string{filepath.Join(testFixture("fix"), "template.json")}
+	if code := c.Run(args); code != 0 {
+		fatalCommand(t, c.Meta)
+	}
+}
+
+func TestFix_invalidTemplate(t *testing.T) {
+	c := &FixCommand{
+		Meta: testMeta(t),
+	}
+
+	args := []string{filepath.Join(testFixture("fix-invalid"), "template.json")}
+	if code := c.Run(args); code != 1 {
+		fatalCommand(t, c.Meta)
+	}
+}
+
+func TestFix_invalidTemplateDisableValidation(t *testing.T) {
+	c := &FixCommand{
+		Meta: testMeta(t),
+	}
+
+	args := []string{
+		"-validate=false",
+		filepath.Join(testFixture("fix-invalid"), "template.json"),
+	}
+	if code := c.Run(args); code != 0 {
+		fatalCommand(t, c.Meta)
+	}
+}

command/test-fixtures/fix-invalid/template.json

@@ -0,0 +1,3 @@
+{
+    "hello": "world"
+}

command/test-fixtures/fix/template.json

@@ -0,0 +1,7 @@
+{
+    "builders": [{"type": "dummy"}],
+
+    "push": {
+        "name": "foo/bar"
+    }
+}