boost-bootstrap-function

REQUIRED BACKGROUND: boost-start. For middleware → boost-bootstrap-middleware. For Pub/Sub adapter specifics (incl. ctx-loss workaround) → boost-bootstrap-adapter-pubsub.

Iron Law — handler signature is forced by function.Handler[T]

The framework declares (bootstrap/function/handler.go):

type Handler[T any] func(context.Context, cloudevents.Event) (T, error)

Input is always cloudevents.Event by value. Instantiate T = *cloudevents.Event so the publisher / logger middlewares — which type-switch on *event.Event — fire correctly.

// CORRECT
func handle(ctx context.Context, in cloudevents.Event) (*cloudevents.Event, error)

// WRONG — return-by-value silently disables publisher middleware
func handle(ctx context.Context, in cloudevents.Event) (cloudevents.Event, error)

// WRONG — does not compile against function.Handler[*cloudevents.Event]
func handle(ctx context.Context, in *cloudevents.Event) (*cloudevents.Event, error)

Wiring

import (
    "github.com/xgodev/boost"
    "github.com/xgodev/boost/bootstrap/function"
    cloudevents "github.com/cloudevents/sdk-go/v2"
)

func main() {
    boost.Start()
    ctx := context.Background()

    // ... build middlewares (see boost-bootstrap-middleware) ...
    // ... build adapter (see boost-bootstrap-adapter-pubsub or analogous) ...

    fn, err := function.New[*cloudevents.Event](rec, lmi, pmi)
    if err != nil { log.Fatalf("function: %v", err) }

    if err := fn.Run(ctx, handle, adapter); err != nil {
        log.Fatalf("run: %v", err)
    }
}

The whole chain must agree on T = *cloudevents.Event: function.New[*cloudevents.Event](...), lm.NewAnyErrorMiddleware[*cloudevents.Event](), apubsub.New[*cloudevents.Event](pb). Mixing T types yields cryptic compile errors at the wiring call.

Red flags

Red flag	Fix
Handler returning cloudevents.Event (value)	Change return to *cloudevents.Event
Handler with input *cloudevents.Event (pointer)	Change to value — framework signature is forced
function.New[cloudevents.Event](...) (T = value)	Change to function.New[*cloudevents.Event](...)
One middleware in the chain parameterized differently from the rest	Pick *cloudevents.Event everywhere

Verification by example: before claiming a handler signature is correct, grep bootstrap/function/handler.go and confirm the actual Handler[T] type signature. The framework is the source of truth; this skill can drift.