Colgen – Collection Generator for Go

Colgen is a powerful Go code generation tool that automates the creation of collection methods and types based on special comment annotations.

Features

• Generates collection types and utility methods from simple annotations
• Supports multiple generation modes:
  • Base collection types ([]Struct)
  • Field value collectors
  • Unique field value collectors
  • Group slice by field
  • Converters and Index functions
• AI-assisted review/readme/tests generation
• Code injection capabilities
• Customizable through command-line flags

Installation

go install github.com/vmkteam/colgen/cmd/colgen@latest

Usage

Comment Format

//go:generate colgen
//colgen:News,Category,Tag
//colgen:News:TagIDs,UniqueTagIDs,Map(db),UUID
//colgen:Episode:ShowIDs,MapP(db.SiteUser),Index(MovieID),Group(ShowID)
//colgen:Show:MapP(db)
//colgen:Season:mapp(db)

Command Line Flags

Flag	Description	Default
-list	Use "List" suffix for collections	false
-imports	Custom import paths (comma-separated)	""
-funcpkg	Package for Map & MapP functions	""
-write-key	Write assistant key to homedir	""
-ai	Choose assistant whose key is being written	"deepseek"

Generation Modes

Base Generators

For //colgen:<struct>,<struct>,...:

• Creates type <struct>s []<struct>
• Generates methods:
  • IDs() []<id type> - Returns all IDs in slice
  • Index() map[<id type>]<struct> - Returns map of ID to struct

Custom Generators

• Index(field) - Create index by specified field (default: ID)
• Group(field) - Group slice by specified field
• <Field> - Collect all values from field
• Unique<Field> - Collect unique values from field
• MapP - Generate mapping function with package prefix
• Map - Generate mapping function (can be lowercase for private)

Inline Mode

//colgen@NewCall(db)
//colgen@newUserSummary(newsportal.User,full,json)

AI Assistance

colgen -write-key=<deepseek key>

It writes deepseek key to the config file. If you want to use claude, run:

colgen -write-key=<claude key> -ai=claude

Supported assistants at the moment: deepseek, claude.

Note: if you run it not the first time, it replaces only key of chosen assistant. So, you can add both keys and choose assistant to run from a special comment.

//go:generate colgen 
//colgen@ai:<readme|review|tests>

Examples:

//go:generate colgen 
//colgen@ai:readme           // makes readme using deepseek by default
//colgen@ai:tests(deepseek)  // makes tests using deepseek explicitly
//colgen@ai:review(claude)   // makes review using claude