gistfile1.txt

$ go run main.go
Config.Registration: doc: "The plugin to use for sending Registration data, when this is unset or empty sending registration data is disabled "

main.go

package main

import (
  "fmt"
  "go/ast"
  "go/parser"
  "go/token"
  "strings"
)


type Config struct {
  // @doc The plugin to use for sending Registration data,
  // when this is unset or empty sending registration data is disabled
  Registration              []string `confkey:"registration" type:"comma_split" default:""`
  RegistrationCollective    string   `confkey:"registration_collective"` // The Sub Collective to publish registration data to
}

// since I check for `Config` this should all be skipped
type Other struct {
  // @doc the wrong documentation
  Registration              []string `confkey:"registration" type:"comma_split" default:""`
  RegistrationCollective    string   `confkey:"registration_collective"` // The Sub Collective to publish registration data to
}

func parseDocString(d string) string {
  d = strings.TrimPrefix(d, "@doc ")
  d = strings.ReplaceAll(d, "\n", " ")

  return d
}

func parseGoFile(f string, structName string) error {
  d, err := parser.ParseFile(token.NewFileSet(), f, nil, parser.ParseComments)
  if err != nil {
    fmt.Println(err)
    return nil
  }

  ast.Inspect(d, func(n ast.Node) bool {
    switch t := n.(type) {
    case *ast.TypeSpec:
      return t.Name.Name == structName
    case *ast.StructType:
      for _, field := range t.Fields.List {
        tag := ""
        doc := ""

        if field.Tag != nil && field.Tag.Kind == token.STRING {
          tag = field.Tag.Value
        }

        switch {
        case strings.HasPrefix(field.Doc.Text(), "@doc"):
          doc = field.Doc.Text()
        case strings.HasPrefix(field.Comment.Text(), "@doc"):
          doc = field.Comment.Text()
        }

        if strings.Contains(tag, "confkey") && doc != "" {
          fmt.Printf("%s.%s: doc: %q\n", structName, field.Names[0].Name, parseDocString(doc))
        }
      }
    }

    return true
  })

  return nil
}

func main() {
  parseGoFile("main.go", "Config")
}