validator

validator

Struct field validation via tags. Supports nonzero and email rules.

Problem

Go applications frequently need to validate user input, config values, or API payloads before processing them. The standard library has no built-in struct validation — every project ends up writing boilerplate if checks. This package provides a small, tag-based validator with zero external dependencies.

Quick start

import "github.com/azghr/forge/validator"

type User struct {
    Name  string `validate:"nonzero"`
    Email string `validate:"email"`
}

u := User{Name: "Alice", Email: "x@x"}
if err := validator.ValidateStruct(u); err != nil {
    log.Fatal(err)
}

API

Functions

• ValidateStruct(v interface{}, opts ...Option) error — validate all exported fields of a struct by their validate tags. Returns a ValidationError on failure, or nil if all fields pass.

Options

• WithTagName(name string) Option — set the struct tag key (default "validate").

Supported tags

Tag	Applies to	Description
nonzero	string, int, bool, ptr, slice, map, etc.	Value must not be the zero value for its type
email	string	Value must match a basic email pattern

Error types

• ValidationError — []FieldError that implements error. Each FieldError contains Field (name), Tag (failed rule), and Value.

Performance

Uses reflection once per call. Benchmark on Apple M1 Max:

• Valid struct: ~500 ns/op
• Invalid struct: ~600 ns/op