notag

A tiny Go linter that ensures specific struct tags are not used globally or in designated packages.

Why Use notag?

Your project, your rules!

But seriously, it's incredibly useful for maintaining clean architecture. For example, when you have:

• Controller/API layer → JSON tags belong here for request/response structs
• Business logic layer → No JSON tags needed, keeps internal structs clean
• Data layer → Different serialization needs

This prevents confusion and enforces architectural boundaries, saving debugging time and maintaining code clarity.

┌─────────────────────────────────────────┐
│            API/Controller Layer         │
│  ┌─────────────────────────────────────┐│
│  │ type UserRequest struct {           ││  ✅ JSON tags OK
│  │     Name  string `json:"name"`      ││
│  │     Email string `json:"email"`     ││
│  │ }                                   ││
│  └─────────────────────────────────────┘│
└─────────────────────────────────────────┘
                    │
                    ▼
┌─────────────────────────────────────────┐
│         Business Logic Layer            │
│  ┌─────────────────────────────────────┐│
│  │ type User struct {                  ││  ❌ notag catches this!
│  │     Name  string `json:"name"`      ││
│  │     Email string                    ││
│  │ }                                   ││
│  └─────────────────────────────────────┘│
└─────────────────────────────────────────┘
                    │
                    ▼
┌─────────────────────────────────────────┐
│              Data Layer                 │
│  ┌─────────────────────────────────────┐│
│  │ type UserEntity struct {            ││  ✅ DB tags OK
│  │     ID    int    `db:"id"`          ││
│  │     Name  string `db:"name"`        ││
│  │     Email string `db:"email"`       ││
│  │ }                                   ││
│  └─────────────────────────────────────┘│
└─────────────────────────────────────────┘

Installation

go install github.com/guerinoni/notag@latest

Usage

Package-specific Tag Restrictions

# Warn if JSON tags are found in the "service" package
notag -denied-pkg service:json ./...

# Multiple packages with different restrictions
notag -denied-pkg service:json -denied-pkg repository:xml ./...

Package Path-based Restrictions

# Deny XML tags in the "repository" package
notag -denied-pkg-path github.com/guerinoni/notag/analyzer:xml ./...

Global Tag Restrictions

# Deny validate and xml tags globally across all packages
notag -denied validate,xml ./...

# Combine global and package-specific rules
notag -denied validate -denied-pkg service:json ./...

All combination of restrictions

# This denys:
# globally db tags,
# in the "service" package: json tags,
# in the "github.com/org/be/internal/controllers" package: xml tags
notag --denied db --denied-pkg service:json --denied-pkg-path github.com/org/be/internal/controllers:xml ./...

Benefits

Instead of littering your internal structs with json:"-" tags, notag encourages you to:

• Keep API request/response structs in dedicated packages
• Maintain clean internal domain models
• Change serialization formats without touching business logic
• Have explicit control over what gets exposed in your API

Features

• Global tag restrictions
• Package-specific tag restrictions
• Combine global + pkg specific directive
• Multiple tag support
• Package path-based restrictions
• Find in nested structs (coming soon)