Validation Hook

The validation hook enforces event schema contracts at runtime. When an event is dispatched, the hook fetches its spec from the registry and validates all properties against the JSON Schema — before any provider receives the event.

Setup

Go

import (
    "github.com/dejanradmanovic/event-spec/hooks/validation"
    "github.com/dejanradmanovic/event-spec/registry/local"
    "github.com/dejanradmanovic/event-spec/spec"
)

reg, _ := local.New(local.Config{SpecsDir: "./specs"})

lookup := func(name string) (*spec.EventDef, bool) {
    def, err := reg.GetEvent(ctx, namespace, name, "")
    if err != nil {
        return nil, false
    }
    return def, true
}

client := analytics.NewClient(
    analytics.WithProviders(amp),
    analytics.WithHooks(validation.New(lookup)),
)

TypeScript

import { ValidationHook } from '@dejanradmanovic/event-spec-api';

const hook = new ValidationHook({
    lookup: async (name) => {
        const def = await registry.getEvent('ecommerce', name, '');
        return def ?? null;
    },
});

const client = new Client({
    providers: [amp],
    hooks: [hook],
});

Kotlin

import io.eventspec.analytics.ValidationHook

val hook = ValidationHook { eventName, properties ->
    // Return an error message string, or null if valid.
    val schema = schemaRegistry[eventName] ?: return@ValidationHook null
    schema.validate(properties)
}

val client = Client(ClientOptions(
    providers = listOf(amp),
    hooks = listOf(hook),
))

Behavior

Scenario	Outcome
Event matches spec	Passes through to providers
Missing required property	Dropped + error logged
Wrong type (e.g. integer for string)	Dropped + error logged
Unknown event name (no spec found)	Configurable: pass or drop
status: deprecated event	Warning logged, event passes
status: deleted event	Dropped

What gets validated

• Required properties are present and non-null
• Property types match the spec (string, number, integer, boolean, object, array)
• Enum constraints — value must be one of the declared enum values
• Pattern constraints — string matches the regex pattern
• Minimum / maximum constraints — number is within range