Merge pull request #1 from gostaticanalysis/add-tempalte-options

Add TemplateOption

template.go

@@ -11,9 +11,44 @@ import (
 	"golang.org/x/tools/txtar"
 )
 
+// DefaultFuncMap is a default functions which using in a template.
+var DefaultFuncMap = template.FuncMap{
+	"gitkeep": func() string {
+		return ".gitkeep"
+	},
+	"gomod": func() string {
+		return "go.mod"
+	},
+	"gomodinit": func(path string) string {
+		f, err := ModInit(path)
+		if err != nil {
+			panic(err)
+		}
+		return f
+	},
+}
+
+// TemplateOption is an option for a template.
+// It can decorate the template.
+type TemplateOption func(*template.Template) (*template.Template, error)
+
+// TemplateWithFuncs add funcs to a template.
+func TemplateWithFuncs(funcs template.FuncMap) TemplateOption {
+	return func(tmpl *template.Template) (*template.Template, error) {
+		return tmpl.Funcs(funcs), nil
+	}
+}
+
+// TemplateWithDelims sets delims of a template.
+func TemplateWithDelims(left, right string) TemplateOption {
+	return func(tmpl *template.Template) (*template.Template, error) {
+		return tmpl.Delims(left, right), nil
+	}
+}
+
 // ParseTemplate parses a template which represents as txtar format from given a file system.
 // The name is template name. If stripPrefix is not empty string, ParseTemplate uses sub directory of stripPrefix.
-func ParseTemplate(tmplFS fs.FS, name, stripPrefix string) (*template.Template, error) {
+func ParseTemplate(tmplFS fs.FS, name, stripPrefix string, options ...TemplateOption) (*template.Template, error) {
 	fsys := tmplFS
 	if stripPrefix != "" {
 		var err error
@@ -28,21 +63,15 @@ func ParseTemplate(tmplFS fs.FS, name, stripPrefix string) (*template.Template,
 		return nil, err
 	}
 
-	return template.New(name).Delims("@@", "@@").Funcs(template.FuncMap{
-		"gitkeep": func() string {
-			return ".gitkeep"
-		},
-		"gomod": func() string {
-			return "go.mod"
-		},
-		"gomodinit": func(path string) string {
-			f, err := ModInit(path)
-			if err != nil {
-				panic(err)
-			}
-			return f
-		},
-	}).Parse(string(txtar.Format(ar)))
+	tmpl := template.New(name).Delims("@@", "@@").Funcs(DefaultFuncMap)
+	for _, opt := range options {
+		tmpl, err = opt(tmpl)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return tmpl.Parse(string(txtar.Format(ar)))
 }
 
 // ExecuteTemplate executes a template with data.