# registerLocalModules

Register one or many local module(s). During the registration process, the specified registration function will be invoked with a FireflyRuntime instance and an optional context object. To defer the registration of specific routes or navigation items, a registration function can return an anonymous function.

A local module is a regular module that is part of the host application build and is bundled at build time, as opposed to remote module which is loaded at runtime from a remote server. Local modules are particularly valuable when undergoing a migration from a monolithic application to a federated application or when launching a new product with an evolving business domain.

# Reference

registerLocalModules(registerFunctions: [], runtime, options?: { context? })

# Parameters

registerFunctions: An array of ModuleRegisterFunction.
runtime: A FireflyRuntime instance.
options: An optional object literal of options:
- context: An optional context object that will be pass to the registration function.

# Returns

A Promise object with an array of LocalModuleRegistrationError if any error happens during the registration.

LocalModuleRegistrationError:
- error: The original error object.

# Usage

# Register a local module

host/src/bootstrap.tsx
import { registerLocalModules, FireflyRuntime } from "@squide/firefly";
import { register } from "@sample/local-module";

const runtime = new FireflyRuntime();

await registerLocalModules([register], runtime);

local-module/src/register.tsx
import type { ModuleRegisterFunction, FireflyRuntime } from "@squide/firefly";
import { AboutPage } from "./AboutPage.tsx";

export const register: ModuleRegisterFunction<FireflyRuntime> = async runtime => {
    runtime.registerRoute({
        path: "/about",
        element: <AboutPage />
    });

    runtime.registerNavigationItem({
        $label: "About",
        to: "/about"
    });
}

Sometimes, data must be fetched to determine which routes or navigation items should be registered by a given module. To address this, Squide offers a two-phase registration mechanism:

The first phase allows modules to register their routes and navigation items that are not dependent on initial data (in addition to their MSW request handlers when fake endpoints are available).
The second phase enables modules to register routes and navigation items that are dependent on initial data. Such a use case would be determining whether a route should be registered based on a feature flag. We refer to this second phase as deferred registrations.

To defer a registration to the second phase, a module registration function can return an anonymous function. Once the modules are registered and the completeLocalModuleRegistrations function is called, the deferred registration functions will be executed.

host/src/bootstrap.tsx
import { completeLocalModuleRegistrations, registerLocalModules, FireflyRuntime } from "@squide/firefly";
import { register } from "@sample/local-module";
import { fetchFeatureFlags } from "@sample/shared";

const runtime = new FireflyRuntime();

await registerLocalModules([register], runtime);

// Don't fetch data in the bootstrapping code for a real application. This is done here
// strictly for demonstration purpose.
const featureFlags = await fetchFeatureFlags();

// Complete the module registrations with the feature flags data.
await completeLocalModuleRegistrations(runtime, { featureFlags });

local-module/src/register.tsx
import type { ModuleRegisterFunction, FireflyRuntime } from "@squide/firefly";
import type { DeferredRegistrationData } from "@sample/shared";
import { AboutPage } from "./AboutPage.tsx";
import { FeatureAPage } from "./FeatureAPage.tsx";

export const register: ModuleRegisterFunction<FireflyRuntime, unknown, DeferredRegistrationData> = async runtime => {
    runtime.registerRoute({
        path: "/about",
        element: <AboutPage />
    });

    runtime.registerNavigationItem({
        $label: "About",
        to: "/about"
    });

    // Once the feature flags has been loaded by the host application, by completing the module registrations process,
    // the deferred registration function will be called with the feature flags data.
    return ({ featureFlags } = {}) => {
        // Only register the "feature-a" route and navigation item if the feature is active.
        if (featureFlags.featureA) {
            runtime.registerRoute({
                path: "/feature-a",
                element: <FeatureAPage />
            });

            runtime.registerNavigationItem({
                $label: "Feature A",
                to: "/feature-a"
            });
        }
    };
}

completeLocalModuleRegistrations

../completelocalmoduleregistrations/

# Handle the registration errors

host/src/bootstrap.tsx
import { registerLocalModules, FireflyRuntime } from "@squide/firefly";
import { register } from "@sample/local-module";

const runtime = new FireflyRuntime();

(await registerLocalModules([register], runtime)).forEach(x => {
    console.log(x);
});