packer: template process build names [GH-744]

CHANGELOG.md

@@ -39,6 +39,8 @@ IMPROVEMENTS:
 * core: Plugins communicate over a single TCP connection per plugin now,
   instead of sometimes dozens. Performance around plugin communication
   dramatically increased.
+* core: Build names are now template processed so you can use things
+  like user variables in them. [GH-744]
 * builder/amazon/all: Launched EC2 instances now have a name of
   "Packer Builder" so that they are easily recognizable. [GH-642]
 * builder/amazon/all: Copying AMIs to multiple regions now happens

command/inspect/command.go

@@ -142,5 +142,9 @@ func (c Command) Run(env packer.Environment, args []string) int {
 		}
 	}
 
+	ui.Say("\nNote: If your build names contain user variables or template\n" +
+		"functions such as 'timestamp', these are processed at build time,\n" +
+		"and therefore only show in their raw form here.")
+
 	return 0
 }

packer/template.go

@@ -446,6 +446,39 @@ func (t *Template) Build(name string, components *ComponentFinder) (b Build, err
 		return
 	}
 
+	// Prepare the variables
+	var varErrors []error
+	variables := make(map[string]string)
+	for k, v := range t.Variables {
+		if v.Required && !v.HasValue {
+			varErrors = append(varErrors,
+				fmt.Errorf("Required user variable '%s' not set", k))
+		}
+
+		var val string = v.Default
+		if v.HasValue {
+			val = v.Value
+		}
+
+		variables[k] = val
+	}
+
+	if len(varErrors) > 0 {
+		return nil, &MultiError{varErrors}
+	}
+
+	// Process the name
+	tpl, err := NewConfigTemplate()
+	if err != nil {
+		return nil, err
+	}
+	tpl.UserVars = variables
+
+	name, err = tpl.Process(name, nil)
+	if err != nil {
+		return nil, err
+	}
+
 	// Gather the Hooks
 	hooks := make(map[string][]Hook)
 	for tplEvent, tplHooks := range t.Hooks {
@@ -542,27 +575,6 @@ func (t *Template) Build(name string, components *ComponentFinder) (b Build, err
 		provisioners = append(provisioners, coreProv)
 	}
 
-	// Prepare the variables
-	var varErrors []error
-	variables := make(map[string]string)
-	for k, v := range t.Variables {
-		if v.Required && !v.HasValue {
-			varErrors = append(varErrors,
-				fmt.Errorf("Required user variable '%s' not set", k))
-		}
-
-		var val string = v.Default
-		if v.HasValue {
-			val = v.Value
-		}
-
-		variables[k] = val
-	}
-
-	if len(varErrors) > 0 {
-		return nil, &MultiError{varErrors}
-	}
-
 	b = &coreBuild{
 		name:           name,
 		builder:        builder,

packer/template_test.go

@@ -688,6 +688,48 @@ func TestTemplate_BuildUnknownBuilder(t *testing.T) {
 	}
 }
 
+func TestTemplateBuild_names(t *testing.T) {
+	data := `
+	{
+		"variables": {
+			"foo": null
+		},
+
+		"builders": [
+			{
+				"name": "test1",
+				"type": "test-builder"
+			},
+			{
+				"name": "test2-{{user \"foo\"}}",
+				"type": "test-builder"
+			}
+		]
+	}
+	`
+
+	template, err := ParseTemplate([]byte(data), map[string]string{"foo": "bar"})
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	b, err := template.Build("test1", testComponentFinder())
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if b.Name() != "test1" {
+		t.Fatalf("bad: %#v", b.Name())
+	}
+
+	b, err = template.Build("test2-{{user \"foo\"}}", testComponentFinder())
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if b.Name() != "test2-bar" {
+		t.Fatalf("bad: %#v", b.Name())
+	}
+}
+
 func TestTemplate_Build_NilBuilderFunc(t *testing.T) {
 	data := `
 	{