Skill: samber/golang-google-wire (version 1.0.2)

--- name: golang-google-wire description: "Compile-time dependency injection in Golang using google/wire — wire.NewSet, wire.Build, wire.Bind (interface→concrete), wire.Struct, wire.Value, wire.InterfaceValue, wire.FieldsOf, cleanup functions, //go:build wireinject injector files, and generated wire_gen.go. Apply when using or adopting google/wire, when the codebase imports `github.com/google/wire`, or when wiring an application graph at compile time via `wire.Build`. For runtime DI with reflection, see `samber/cc-skills-golang@golang-uber-dig` skill." user-invocable: true license: MIT compatibility: Designed for Claude Code or similar AI coding agents, and for projects using Golang. metadata: author: samber version: "1.0.2" openclaw: emoji: "🪡" homepage: https://github.com/samber/cc-skills-golang requires: bins: - go - wire install: - kind: go package: github.com/google/wire/cmd/wire@latest bins: [wire] skill-library-version: "0.7.0" allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(golangci-lint:*) Bash(git:*) Agent WebFetch mcp__context7__resolve-library-id mcp__context7__query-docs Bash(wire:*) --- **Persona:** You are a Go architect using wire for compile-time DI. You let the compiler catch missing dependencies, treat `wire_gen.go` as committed source, and re-run `wire ./...` after every graph change. # Using google/wire for Compile-Time Dependency Injection in Go Code-generation DI toolkit. Wire resolves the dependency graph at compile time and emits plain Go constructor calls — no runtime container, no reflection. Errors appear when you run `wire ./...`, not at first request. Note: `google/wire` was archived in August 2025 (feature-complete; bug fixes still accepted). **Official Resources:** [pkg.go.dev](https://pkg.go.dev/github.com/google/wire) · [github.com/google/wire](https://github.com/google/wire) · [User Guide](https://github.com/google/wire/blob/main/docs/guide.md) · [Best Practices](https://github.com/google/wire/blob/main/docs/best-practices.md) This skill is not exhaustive. Please refer to library documentation and code examples for more information. Context7 can help as a discoverability platform. ```bash go get -tool github.com/google/wire/cmd/wire@latest go get github.com/google/wire ``` ## wire vs. Runtime DI | Concern | wire | dig / fx / samber/do | | ----------------- | ------------------------- | ---------------------- | | Resolution | Compile time (codegen) | Runtime (reflection) | | Error detection | `wire ./...` fails | First `Invoke`/startup | | Runtime container | None — plain Go calls | Present | | Lifecycle hooks | Not built in | fx: OnStart/OnStop | | Generated files | `wire_gen.go` (committed) | None | For lifecycle, lazy loading, and a full matrix see `samber/cc-skills-golang@golang-dependency-injection`. ## Providers A provider is any Go function — inputs are dependencies, outputs are provided types. Three return forms: ```go func NewConfig() *Config { return &Config{Addr: ":8080"} } func NewDB(cfg *Config) (*sql.DB, error) { return sql.Open("postgres", cfg.DSN) } func NewRedis(cfg *Config) (*redis.Client, func(), error) { // cleanup chained in reverse order c := redis.NewClient(&redis.Options{Addr: cfg.RedisAddr}) return c, func() { c.Close() }, nil } ``` ## Provider Sets `wire.NewSet` groups providers for reuse. Sets can reference other sets. ```go // infra/wire.go var InfraSet = wire.NewSet( NewConfig, NewDB, NewRedis, ) // service/wire.go var ServiceSet = wire.NewSet( NewUserRepo, NewUserService, wire.Bind(new(UserStore), new(*UserRepo)), // interface binding ) ``` Keep sets small: library sets expose a stable surface (adding inputs or removing outputs breaks downstream injectors). One set per package is a useful default. ## Injectors and `//go:build wireinject` The injector file declares the initialization function. Wire generates its body into `wire_gen.go` and replaces the stub. ```go //go:build wireinject package main import "github.com/google/wire" // Wire generates the body of this function. func InitApp() (*App, func(), error) { wire.Build(InfraSet, ServiceSet, NewApp) return nil, nil, nil // replaced by codegen } ``` The `//go:build wireinject` tag prevents the stub from being compiled into the binary — only `wire_gen.go` (which has no such tag) makes it through `go build`. Without this tag, both files define the same function, causing a compile error. Alternative syntax when a dummy return is inconvenient: ```go func InitApp() (*App, func(), error) { panic(wire.Build(InfraSet, ServiceSet, NewApp)) } ``` ## Interface Bindings Wire forbids implicit interface satisfaction — you must declare bindings explicitly so the graph is unambiguous when multiple types implement the same interface. ```go var Set = wire.NewSet( NewPostgresUserRepo, wire.Bind(new(UserStore), new(*PostgresUserRepo)), // tell wire: *PostgresUserRepo satisfies UserStore ) ``` Explicit bindings prevent graph breakage when a new type implementing the same interface is added elsewhere. ## Struct Providers and Values `wire.Struct` fills struct fields from the graph without a manual constructor. Tag fields `wire:"-"` to exclude them. ```go wire.Struct(new(Server), "Logger", "DB") // inject named fields wire.Struct(new(Server), "*") // inject all non-excluded fields wire.Value(Foo{X: 42}) // constant expression (no fn calls / channels) wire.InterfaceValue(new(io.Reader), os.Stdin) // interface-typed literal wire.FieldsOf(new(Config), "DSN", "Addr") // promote struct fields as graph nodes ``` See [advanced.md](references/advanced.md) for the `wire:"-"` exclusion tag and `wire.FieldsOf` details. ## Disambiguating Duplicate Types Wire forbids two providers for the same type. Wrap the underlying type in distinct named types so each has exactly one provider: ```go type PrimaryDSN string type ReplicaDSN string ``` ## Full Application Example ```go // wire.go — injector, excluded from binary via build tag //go:build wireinject package main func InitApp() (*App, func(), error) { wire.Build(config.ConfigSet, infra.InfraSet, service.ServiceSet, NewApp) return nil, nil, nil } // main.go func main() { app, cleanup, err := InitApp() if err != nil { log.Fatal(err) } defer cleanup() app.Run() } ``` Wire generates `wire_gen.go` (plain Go, committed, DO NOT EDIT). For a full example with per-package sets, cleanup-heavy graphs, and generated output, see [recipes.md](references/recipes.md). ## Codegen Workflow ```bash wire ./... # regenerate all injectors in the module wire check ./... # validate graph without regenerating (fast CI check) ``` Run `wire ./...` after every constructor signature change. Add `//go:generate go run github.com/google/wire/cmd/wire` to injector files so `go generate ./...` also works. Commit `wire_gen.go` — it must stay in sync for CI builds. ## Best Practices 1. Never edit `wire_gen.go` — it is overwritten on every `wire ./...` run. Treat it as a build artifact that happens to be committed; source of truth is the provider and injector files. 2. Always add `//go:build wireinject` to injector files — omitting it causes duplicate-symbol compile errors because both the stub and the generated file define the same function. 3. Use named types to distinguish values of the same underlying type — wire enforces one provider per type; named types like `type DSN string` let you have `PrimaryDSN` and `ReplicaDSN` coexist. 4. Keep library provider sets minimal and backward-compatible — adding new required inputs breaks downstream injectors; removing outputs does too. Introduce only newly-created types in the same release. 5. Return `(T, func(), error)` from cleanup providers and let wire chain them — wire generates the correct reverse-order cleanup and handles partial failures (if construction fails midway, only already-built cleanups run). 6. Keep injector files focused — one function per file, one package import at a time. Fat injectors with dozens of `wire.Build` arguments are hard to reason about; delegate to per-package sets. ## Common Mistakes | Mistake | Fix | | --- | --- | | Editing `wire_gen.go` manually | Never edit it. Change providers or injectors and re-run `wire ./...`. | | Missing `//go:build wireinject` | Add the tag as the very first line of every injector file. | | Two providers returning `*sql.DB` | Wrap with a named struct type: `type PrimaryDB struct { *sql.DB }` — Wire does not distinguish pointer type aliases. | | Injecting an interface without `wire.Bind` | Add `wire.Bind(new(MyInterface), new(*MyImpl))` to the provider set. | | Forgetting to re-run `wire ./...` after changes | Run wire before `go build`; add it to `go generate` or a Makefile target. | | Calling `cleanup()` without guarding for nil | Wire returns nil cleanup on construction error; guard with `if cleanup != nil { defer cleanup() }`. | ## Testing Wire generates plain Go constructors, so unit tests use manual injection — no container to clone or reset. For testing patterns (test injectors swapping real providers for fakes, CI stale-check for `wire_gen.go`), see [testing.md](references/testing.md). ## Further Reading - [advanced.md](references/advanced.md) — cleanup chains, multiple injectors, set nesting, error catalogue, codegen flags, quick reference - [recipes.md](references/recipes.md) — HTTP server, multi-injector build, cleanup-heavy graph, CLI embedding - [testing.md](references/testing.md) — test injectors, fake bindings, CI stale check ## Cross-References - → See `samber/cc-skills-golang@golang-dependency-injection` skill for DI concepts and library comparison - → See `samber/cc-skills-golang@golang-uber-dig` skill for runtime reflection-based DI without lifecycle - → See `samber/cc-skills-golang@golang-uber-fx` skill for runtime DI with lifecycle hooks, modules, and signal-aware Run() - → See `samber/cc-skills-golang@golang-samber-do` skill for generics-based DI without reflection - → See `samber/cc-skills-golang@golang-structs-interfaces` skill for interface design patterns - → See `samber/cc-skills-golang@golang-testing` skill for general testing patterns If you encounter a bug or unexpected behavior in google/wire, open an issue at <https://github.com/google/wire/issues>.


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