ifacegen

README

ifacegen

ifacegen is a Go code generation tool that scans Go packages to automatically generate interfaces based on struct method sets. It's particularly useful for creating abstractions such as Service, Repository, or similar patterns.

Features

• Generates interfaces for structs matching configurable name patterns (e.g., *Service, *Repository).
• Skips specific structs or methods via // ifacegen:skip comment.
• Includes structs explicitly marked with // ifacegen:generate, even if their name doesn't match patterns.
• Preserves method comments in the generated interfaces.
• Resolves types using go/types for accurate imports and signatures.
• Handles cross-package imports with proper aliasing.
• Concurrently processes multiple packages for improved performance.
• Outputs one file per package (default name: iface_gen.go).
• Formats generated output with gofmt.

Installation

go install github.com/seyyedaghaei/ifacegen/cmd/ifacegen@latest

Usage

Basic Usage

ifacegen --match '*Service,*Repository' --output iface_gen.go ./...

Interactive Mode

For easy configuration, use interactive mode:

ifacegen --interactive

Advanced Examples

# Dry run to see what would be generated
ifacegen --dry-run --match '*Service' ./...

# Watch mode for development
ifacegen --watch --match '*Service' ./...

# Verbose output with progress indicators
ifacegen --verbose --match '*Service,*Repository' ./...

# Custom interface naming
ifacegen --name '{}Interface' --match '*Service' ./...

Flags

Flag	Description
--match, -m	Comma-separated list of glob patterns to match struct names (e.g., *Service). Use --match or -m, not -match.
--output, -o	Output filename used inside each package (default: iface_gen.go). Use --output or -o, not -output.
--name, -n	Pattern for naming interfaces, using {} as the placeholder (default: I{}). Use --name or -n, not -name.
--dry-run, -d	Show what would be generated without writing files.
--verbose, -V	Enable verbose output with detailed logging.
--watch, -w	Watch for file changes and regenerate automatically.
--progress, -p	Show progress indicators (default: true).
--interactive, -i	Start interactive configuration mode.
--version, -v	Show version information.
--help, -h	Show usage information.

Skipping and Including Structs or Methods

You can exclude specific structs or methods from interface generation using the // ifacegen:skip comment:

// ifacegen:skip
type AuthService struct {
	// ...
}

// ifacegen:skip
func (s *UserService) InternalLogic() {}

You can explicitly include structs (even if they don't match --match) with the // ifacegen:generate comment:

// ifacegen:generate
type Special struct {
	// ...
}

You can override the interface name with // ifacegen:name:

// ifacegen:name IOAuthStateRepository
type oauthStateRepository struct {
	// ...
}

Example

Given this struct:

// UserService handles user-related operations.
type UserService struct {}

func (s *UserService) CreateUser(name string) error {
	return nil
}

func (s *UserService) GetUser(id int) (*User, error) {
	return nil, nil
}

Running:

ifacegen --match '*Service' ./...

Generates:

// Code generated by ifacegen. DO NOT EDIT.
package yourpackage

// UserService handles user-related operations.
type IUserService interface {
	CreateUser(name string) error
	GetUser(id int) (*User, error)
}

CLI Features

Interactive Mode

The --interactive / -i flag starts a guided configuration process:

• Step-by-step setup of all options
• Preview of generated command
• Confirmation before execution

Dry Run Mode

Use --dry-run / -d to preview what would be generated:

• Shows which files would be created/updated
• Displays file size changes
• No actual files are written

Watch Mode

Use --watch / -w for development workflows:

• Automatically regenerates when files change
• Polls for changes every 2 seconds
• Perfect for development environments

Progress Indicators

• Real-time progress updates
• Package-by-package status
• Success/failure indicators
• Disable with --progress=false

Verbose Output

Use --verbose / -V for detailed logging:

• Package loading information
• Generation details
• Error context
• File operation logs

Output Location

The generated file is written once per package, in the same directory as the structs, using the filename from --output (default iface_gen.go). If the content hasn't changed, the file won't be overwritten.

Docs

• Development: docs/development.md
• Breaking changes policy: docs/breaking-changes-policy.md
• How it works: docs/how-it-works.md
• Releases: docs/releases.md
• Contributing: CONTRIBUTING.md

License

MIT. See LICENSE.