ifacemaker

ifacemaker

This is a development helper program that generates a Golang interface by inspecting the structure methods of existing .go file(s). The primary use case is to generate interfaces for gomock, so that gomock can generate mocks from those interfaces. This makes unit testing easier.

Origins

• https://github.com/vburenin/ifacemaker
• https://github.com/nkovacs/ifacemaker

Install

go get github.com/mlctrez/ifacemaker

Usage

Here is the help output of ifacemaker:

$ ifacemaker --help
Options:
  
  -h, --help         display help information
  -f, --file        *Go source file or directory to read
  -s, --struct      *Generate an interface for this structure name
  -i, --iface       *Name of the generated interface
  -p, --pkg         *Package name for the generated interface
  -d, --doc[=true]   Copy method documentation from source files.
  -o, --output       Output file name. If not provided, result will be printed to stdout.
  -a, --add-import   An additional import to add to the generated file.
  -r, --rewrite      Rewrites unqualified exports with this package prefix.
$

As an example, let's say you wanted to generate an interface for all methods on the Human struct in this sample code:

package main

import "fmt"

type Human struct {
	name string
	age  int
}

// Returns the name of our Human.
func (h *Human) GetName() string {
	return h.name
}

// Our Human just had a birthday! Increase its age.
func (h *Human) Birthday() {
	h.age += 1
	fmt.Printf("I am now %d years old!\n", h.age)
}

// Make the Human say hello.
func (h *Human) SayHello() {
	fmt.Printf("Hello, my name is %s, and I am %d years old.\n", h.name, h.age)
}

func main() {
	human := &Human{name: "Bob", age: 30}
	human.GetName()
	human.SayHello()
	human.Birthday()
}

The ifacemaker helper program can generate this interface for you:

$ ifacemaker -f human.go -s Human -i HumanIface -p humantest
package humantest

type HumanIface interface {
	// Returns the name of our Human.
	GetName() string
	// Our Human just had a birthday! Increase its age.
	Birthday()
	// Make the Human say hello.
	SayHello()
}

$

In the above example, ifacemaker inspected the structure methods of the Human struct and generated an interface called HumanIface in the humantest package. Note that the ifacemaker program preserves docstrings by default.

You can tell ifacemaker to write its output to a file, versus stdout, using the -o parameter:

$ ifacemaker -f human.go -s Human -i HumanIface -p humantest -o humaniface.go

Additional Imports / Rewrite

Field and return types in the generated interface can be re-written to include the source package name. See scripts/sample.sh for example usage of the --add-import and --rewrite args.

A short example

$ ifacemaker --file ~/go/src/github.com/aws/aws-sdk-go/service/cloudformation/api.go \
  --struct CloudFormation --iface ICloudFormation --pkg icloud \
  --doc=false --rewrite cloudformation

results in this (truncated) output

// ** comments explain additional generated code

package icloud

import (
        "github.com/aws/aws-sdk-go/aws"
        "github.com/aws/aws-sdk-go/aws/request"
        // ** additional import added
        "github.com/aws/aws-sdk-go/service/cloudformation"
)

// ** checks that the interface implements all of the original api
var _ ICloudFormation = (*cloudformation.CloudFormation)(nil)

type ICloudFormation interface {
        // ** *CancelUpdateStackInput rewritten to *cloudformation.CancelUpdateStackInput
        CancelUpdateStackRequest(input *cloudformation.CancelUpdateStackInput) (req *request.Request, output *cloudformation.CancelUpdateStackOutput)
        CancelUpdateStack(input *cloudformation.CancelUpdateStackInput) (*cloudformation.CancelUpdateStackOutput, error)
        CancelUpdateStackWithContext(ctx aws.Context, input *cloudformation.CancelUpdateStackInput, opts ...request.Option) (*cloudformation.CancelUpdateStackOutput, error)
        // remainder omitted
}