gengen

Documentation

Overview

Package gengen provides goagen with the ability to run user provided generators.

How to write a goagen generator package:

The only requirement is that the package expose a global Generate function with the following signature:

func Generate(api *design.APIDefinition) ([]string, error)

where api is the API definition computed from the design DSL. On success Generate should return the path to the generated files. On error the error message gets displayed to the user (and goagen exist with status 1).

The Generate method should take advantage of the APIDefinition IterateXXX methods to iterate through the API resources, media types and types to guarantee that the order doesn't change between two invokation of the function (thereby generating different output even if the design hasn't changed).

The Output directory is available through the codegen.OutputDir global variable. Here is an example of a custom generator package source:

Package genresnames implements a goa generator which creates a file "names.txt" containing the names of the API resources sorted in alphabetical order. invoke with "goagen -d <Go package path to design package> gen --pkg-path=<Go package path to genresnames>"

package genresnames

import (
	"io/ioutil"
	"path/filepath"
	"strings"

	"github.com/raphael/goa/codegen"
	"github.com/raphael/goa/design"
)

// Generate is the function called by goagen to generate the "names.txt" file.
func Generate(api *design.APIDefinition) ([]string, error) {
	names := make([]string, len(api.Resources))
	i := 0
	api.IterateResources(func(res *design.ResourceDefinition) error {
		names[i] = res.Name
		i++
		return nil
	})
	content := strings.Join(names, "\n")
	outputFile := filepath.Join(codegen.OutputDir, "names.txt")
	ioutil.WriteFile(outputFile, []byte(content), 0755)
	return []string{outputFile}, nil
}

Index

• Variables
• type Command
  • func NewCommand() *Command
  • func (c *Command) RegisterFlags(r codegen.FlagRegistry)
  • func (c *Command) Run() ([]string, error)

Variables

var (
	// GenPkgPath contains the path to the third party generator Go package.
	GenPkgPath string

	// GenPkgName contains the name of the third party generator Go package.
	GenPkgName string
)

Types

type Command

type Command struct {
	*codegen.BaseCommand
}

Command is the goa generic generator command line data structure. It implements meta.Command.

func NewCommand

func NewCommand() *Command

NewCommand instantiates a new command.

func (*Command) RegisterFlags

func (c *Command) RegisterFlags(r codegen.FlagRegistry)

RegisterFlags registers the command line flags with the given registry.

func (*Command) Run

func (c *Command) Run() ([]string, error)

Run simply calls the meta generator.