Migrating from v4 to v5

godi v5 is a breaking release. This guide lists every breaking change and the mechanical fix for each. Most upgrades are a find-and-replace plus a single build-error sweep.

A v4 program keeps working on v4 forever — v5 lives at a different import path, so nothing updates until you opt in.

At a glance

Change	Action
Import path `/v4` → `/v5`	Find-and-replace across your module
Go 1.26 minimum	Upgrade your toolchain
`Add*` no longer return errors	Check `Build()` (or `Err()`) instead
Typed errors are now pointers	Match with `errors.AsType[*godi.XxxError]`
`Collection.ToSlice()` returns `[]ServiceInfo`	Use the read-only view fields
`CircularDependencyError` fields are strings	Read `.Node` / `.Path` as strings
`Remove` removes keyed + grouped too	Use `RemoveKeyed` for surgical removal
`optional:"true"` propagates construction failures	Fix the failing constructor, or make it non-optional

1. Import path

v5 modules live under /v5:

// Before
import "github.com/junioryono/godi/v4"
import godigin "github.com/junioryono/godi/v4/gin"

// After
import "github.com/junioryono/godi/v5"
import godigin "github.com/junioryono/godi/v5/gin"

# One-shot for a whole module:
go mod edit -droprequire github.com/junioryono/godi/v4
go get github.com/junioryono/godi/v5@latest
grep -rl 'junioryono/godi/v4' . | xargs sed -i '' 's#junioryono/godi/v4#junioryono/godi/v5#g'
go mod tidy

2. Go 1.26 minimum

v5 uses errors.AsType, context.AfterFunc, and other Go 1.26 features. Bump your go.mod:

go 1.26.0

3. `Add*` methods no longer return errors

This is the largest change. AddSingleton, AddScoped, AddTransient, and AddModules now return nothing. Registration errors are recorded and reported together by Build().

Before

c := godi.NewCollection()
if err := c.AddSingleton(NewLogger); err != nil {
    return err
}
if err := c.AddScoped(NewDatabase); err != nil {
    return err
}

After

c := godi.NewCollection()
c.AddSingleton(NewLogger)
c.AddScoped(NewDatabase)

provider, err := c.Build() // every registration error surfaces here
if err != nil {
    return err
}

Build returns a *godi.BuildError with Phase == "registration" whose cause joins all recorded errors (via errors.Join), so errors.Is / errors.As still match individual causes. Errors recorded inside a module are attributed with the module name.

If you need to inspect registration errors before building, call Collection.Err():

c.AddSingleton(NewLogger)
if err := c.Err(); err != nil {
    // handle recorded registration errors early
}

Module builder functions (godi.AddSingleton(...) inside godi.NewModule) are unchanged in shape — they still compose into a ModuleOption.

4. Typed errors are now pointers

Every typed error is returned as a pointer. Update any error matching that used a value target. With Go 1.26, prefer the generic errors.AsType:

// Before
var resErr godi.ResolutionError
if errors.As(err, &resErr) { ... }

// After (Go 1.26)
if resErr, ok := errors.AsType[*godi.ResolutionError](err); ok { ... }

// After (errors.As, still valid)
var resErr *godi.ResolutionError
if errors.As(err, &resErr) { ... }

This applies to all godi error types, including *godi.LifetimeError and *godi.ModuleError, which were the last value-returning errors in v4. Sentinel checks are unchanged: errors.Is(err, godi.ErrServiceNotFound) still works.

5. `Collection.ToSlice()` returns `[]ServiceInfo`

ToSlice previously returned the internal []*Descriptor (shared, mutable pointers exposing internal wiring). It now returns a read-only snapshot:

type ServiceInfo struct {
    ServiceType reflect.Type
    Key         any       // nil if not keyed
    Group       string    // "" if not grouped
    Lifetime    godi.Lifetime
}

// Before
for _, d := range c.ToSlice() {
    fmt.Println(d.Type, d.Lifetime)
}

// After
for _, info := range c.ToSlice() {
    fmt.Println(info.ServiceType, info.Lifetime)
}

The Descriptor type is no longer exported. If you depended on inspecting its other fields (Constructor, Dependencies, etc.), those were internal wiring and have no replacement; open an issue describing your use case.

6. `CircularDependencyError` exposes strings

The cycle is now reported with human-readable type names instead of an internal node-key type:

// Before: Node graph.NodeKey, Path []graph.NodeKey
// After:
type CircularDependencyError struct {
    Node string
    Path []string
}

The rendered error message (err.Error()) is unchanged.

7. Behavioral changes

These compile without changes but behave differently. All three align the code with what the v4 docs already promised.

Remove[T]() / Collection.Remove now removes all registrations of a type — unkeyed, keyed, and grouped. Use RemoveKeyed[T](key) to remove a single keyed registration.
optional:"true" only forgives a dependency that is not registered. If the dependency is registered but its constructor fails, that error now propagates instead of silently injecting nil. Fix the failing constructor, or drop optional if you intended the failure to be ignored.
Stricter registration validation. Several constructor shapes that v4 silently accepted (and then failed to resolve) are now rejected at registration and reported by Build: a non-final error return, malformed Out structs, a group tag on a non-slice In field, an In struct mixed with other parameters, a field tagged with both name and group, and godi.As combined with a result-object / multi-return / void constructor. If Build newly fails, the constructor was already broken; the error message names the fix.

8. Framework integration changes

If you use the framework integration packages, two helpers were removed:

godihttp.Wrap is removed. Use Handle — it returns an http.HandlerFunc, which already satisfies http.Handler, so it works anywhere Wrap did.
```
// Before
handler := godihttp.Wrap(fn)
// After
handler := godihttp.Handle(fn)
```
godifiber.FromContext is removed. Fiber now attaches the scope to the request’s UserContext (the same context-based access the other integrations use, and what Huma needs), instead of Locals. Retrieve it with the standard helper:
```
// Before
scope := godifiber.FromContext(c)
// After
scope, err := godi.FromContext(c.UserContext())
```

The gin, chi, echo, and net/http integrations are otherwise source-compatible (beyond the /v5 import path).

New in v5: a Huma integration (github.com/junioryono/godi/v5/huma) for typed, OpenAPI-backed APIs.

Verifying your upgrade

go build ./...
go test ./...

If it compiles and your Build() call returns no error, you’re done. If you hit a breaking change not covered here, please open an issue.