replica

A modern, generics-based deep copy library for Go. Drop-in replacement for mitchellh/copystructure.

Features

• Type-safe generics API — no type assertions needed
• Cycle detection — returns error instead of stack overflow
• Struct tags — copy:"ignore" and copy:"shallow"
• Functional options — per-call configuration, no global state
• Zero dependencies — pure Go, no external packages
• Compatibility layer — CopyAny/MustAny for gradual migration

Install

go get github.com/agentine/replica

Usage

import "github.com/agentine/replica"

// Type-safe deep copy
original := MyStruct{Name: "hello", Tags: []string{"a", "b"}}
copied, err := replica.Copy(original)

// Panic on error (for variable initialization)
copied := replica.Must(original)

// With options
copied, err := replica.CopyWith(original,
    replica.WithShallowTypes(reflect.TypeOf(time.Time{})),
)

Struct Tags

type Example struct {
    Normal  string
    Skip    string `copy:"ignore"`   // field is zeroed in copy
    Shallow *Big   `copy:"shallow"`  // shallow copy only
}

Migration from copystructure

Before (copystructure)	After (replica)
copystructure.Copy(v)	replica.CopyAny(v)
copystructure.Must(v)	replica.MustAny(v)
Type assertion: result.(MyType)	replica.Copy(v) (no assertion needed)
copystructure.Copiers[t] = fn	replica.WithCopier(t, fn)
copystructure.ShallowCopiers[t] = true	replica.WithShallowTypes(t)

License

MIT