Golang go/ast.FilterPackage() function example

package go/ast

FilterPackage trims the AST for a Go package in place by removing all names from top-level declarations (including struct field and interface method names, but not from parameter lists) that don't pass through the filter f. If the declaration is empty afterwards, the declaration is removed from the AST. The pkg.Files list is not changed, so that file names and top-level package comments don't get lost.

FilterPackage returns true if there are any top-level declarations left after filtering; it returns false otherwise.

Golang go/ast.FilterPackage() function usage

 func makeRx(names []string) (*regexp.Regexp, error) {
  if len(names) == 0 {
 return nil, fmt.Errorf("no expression provided")
  }
  s := ""
  for i, name := range names {
 if i > 0 {
 s += "|"
 }
 if isRegexp(name) {
 s += name
 } else {
 s += "^" + name + "$" // must match exactly
 }
  }
  return regexp.Compile(s)
 }

 func main() {
 var astFile *ast.File
 var dirname string


 ...

 pkgName := astFile.Name.Name
 if pkgName == "main" {
 return
 }

 pkgPath := strings.TrimPrefix(strings.TrimPrefix(dirname, "/src/"), "pkg/")
 astPkg := ast.Package{
 Name: pkgName,
 Files: map[string]*ast.File{
 filename: astFile,
 },
 }

 rx, _ := makeRx(args)


 filter := func(s string) bool { return rx.MatchString(s) }
 ast.FilterPackage(&astPkg, filter) // <-- here
 ...
 }

References :

https://github.com/fzipp/pythia/blob/master/third_party/go.tools/godoc/cmdline.go

http://golang.org/pkg/go/ast/#FilterPackage