Generate API docs from source comments

api_doc.go

package main

import (
	"go/parser"
	"go/token"
	"io"
	"strings"
)

// APIDoc is an API Documentation generator.
// Any comment (except this one) including :apidoc: will be included.
type APIDoc struct{}

const apiDocHint = ":apidoc:"

func (a APIDoc) Write(w io.Writer) (int, error) {
	// Create the AST by parsing dir
	fset := token.NewFileSet()
	pkgs, err := parser.ParseDir(fset, ".", nil, parser.ParseComments)
	if err != nil {
		panic(err)
	}

	for _, pkg := range pkgs {
		for filename, file := range pkg.Files {
			// skip this file
			if filename == "api_doc.go" {
				continue
			}

			// find :apidoc: comments
			for _, c := range file.Comments {
				if strings.Contains(c.Text(), apiDocHint) {
					text := c.Text()
					text = strings.Replace(text, apiDocHint, "", 1)
					text = strings.Trim(text, "\n")

					w.Write([]byte(text))
					w.Write([]byte("\n"))
					w.Write([]byte("\n"))
				}
			}
		}
	}
	return 0, nil
}