Exemplo n.º 1
0
Arquivo: rewrite.go Projeto: tcard/sgo
// rewriteFile applies the rewrite rule 'pattern -> replace' to an entire file.
func rewriteFile(pattern, replace ast.Expr, p *ast.File) *ast.File {
	cmap := ast.NewCommentMap(fileSet, p, p.Comments)
	m := make(map[string]reflect.Value)
	pat := reflect.ValueOf(pattern)
	repl := reflect.ValueOf(replace)

	var rewriteVal func(val reflect.Value) reflect.Value
	rewriteVal = func(val reflect.Value) reflect.Value {
		// don't bother if val is invalid to start with
		if !val.IsValid() {
			return reflect.Value{}
		}
		for k := range m {
			delete(m, k)
		}
		val = apply(rewriteVal, val)
		if match(m, pat, val) {
			val = subst(m, repl, reflect.ValueOf(val.Interface().(ast.Node).Pos()))
		}
		return val
	}

	r := apply(rewriteVal, reflect.ValueOf(p)).Interface().(*ast.File)
	r.Comments = cmap.Filter(r).Comments() // recreate comments list
	return r
}
Exemplo n.º 2
0
// This example illustrates how to remove a variable declaration
// in a Go program while maintaining correct comment association
// using an ast.CommentMap.
func ExampleCommentMap() {
	// src is the input for which we create the AST that we
	// are going to manipulate.
	src := `
// This is the package comment.
package main

// This comment is associated with the hello constant.
const hello = "Hello, World!" // line comment 1

// This comment is associated with the foo variable.
var foo = hello // line comment 2 

// This comment is associated with the main function.
func main() {
	fmt.Println(hello) // line comment 3
}
`

	// Create the AST by parsing src.
	fset := token.NewFileSet() // positions are relative to fset
	f, err := parser.ParseFile(fset, "src.go", src, parser.ParseComments)
	if err != nil {
		panic(err)
	}

	// Create an ast.CommentMap from the ast.File's comments.
	// This helps keeping the association between comments
	// and AST nodes.
	cmap := ast.NewCommentMap(fset, f, f.Comments)

	// Remove the first variable declaration from the list of declarations.
	f.Decls = removeFirstVarDecl(f.Decls)

	// Use the comment map to filter comments that don't belong anymore
	// (the comments associated with the variable declaration), and create
	// the new comments list.
	f.Comments = cmap.Filter(f).Comments()

	// Print the modified AST.
	var buf bytes.Buffer
	if err := format.Node(&buf, fset, f); err != nil {
		panic(err)
	}
	fmt.Printf("%s", buf.Bytes())

	// output:
	// // This is the package comment.
	// package main
	//
	// // This comment is associated with the hello constant.
	// const hello = "Hello, World!" // line comment 1
	//
	// // This comment is associated with the main function.
	// func main() {
	// 	fmt.Println(hello) // line comment 3
	// }
}