Golang template 包基本原理分析

package main
import (
   "os"
   "text/template"
)
var templateStr = `
package main
func main() {
    fmt.Println("Hello, {{.Name}}!")
}
`
func main() {
   // 创建template对象
   t := template.New("demo")
   // 解析模板内容
   parse, err := t.Parse(templateStr)
   if err != nil {
      panic(err)
   }
   // 执行解析
   data := map[string]string{"Name": "World"}
   err = parse.Execute(os.Stdout, data)
   if err != nil {
      panic(err)
   }
}

package main
func main() {
    fmt.Println("Hello, World!")
}

// src/text/template/template.go
type Template struct {
   name string
   *parse.Tree
   *common
   leftDelim  string
   rightDelim string
}

// src/text/template/exec.go
func (t *Template) Execute(wr io.Writer, data any) error {
   return t.execute(wr, data)
}
func (t *Template) execute(wr io.Writer, data any) (err error) {
   defer errRecover(&err)
   // 使用反射解析传入的参数
   value, ok := data.(reflect.Value)
   ...
   state := &state{
      tmpl: t,
      wr:   wr,
      vars: []variable{{"$", value}},
   }
   ...
   // 遍历节点
   state.walk(value, t.Root)
   return
}

// src/text/template/exec.go
func (s *state) walk(dot reflect.Value, node parse.Node) {
   s.at(node)
   switch node := node.(type) {
   case *parse.ActionNode:
      val := s.evalPipeline(dot, node.Pipe)
      if len(node.Pipe.Decl) == 0 {
         s.printValue(node, val)
      }
   ...
   case *parse.ListNode:
       // 循环遍历节点, 递归 
      for _, node := range node.Nodes {
         s.walk(dot, node)
      }
   ...
   case *parse.TextNode:
      if _, err := s.wr.Write(node.Text); err != nil {
         s.writeError(err)
      }
   ...
}