nova-react

The Nova Facade is a set of interfaces that represent the core framework dependencies of a data-backed UI component in a large application. This allows high value components to be written in a host agnostic fashion and used within any host that implements the Nova contracts.

This package provides a React specific implementation of the contexts etc required to make the host implementations accessible to the Nova component code, with the sister package @nova/types providing a framework agnostic set of contracts.

Prerequisites

In order to use this package without compilation of documents, i.e. to parse string documents at runtime, make sure to add @graphitation/graphql-js-tag as a dependency in your package.json along side with @nova/react.

Bundle size cost

In order to eliminate majority of cost from the bundle, several pre-conditions must be met:

• Your bundler, typescript and package should configured to use ESM/.mjs modules for module resolution
• You should use a transform to parse graphql documents on compile time

Bundler and typescript configuration

In your package, use import and export statements instead of require. In tsconfig.json your module should be set to ES6. Webpack 5 seems to be doing the right thing after the previous two items are done. For Webpack 4, things might not work in a weird way. We recommend updating to Webpack 5. One way we have seen people make it work in webpack 4 is by adding the following to their webpack config. YMMV.

{
  test: /\.mjs$/,
  include: /node_modules/,
  type: "javascript/auto",
},

GraphQL pre-parsing

graphql tag is not meant to be used in runtime outside of development. It brings big dependencies like graphql-js and does query parsing on runtime. Instead consider using one of the transforms that can pre-parse it.

Webpack

For ts-loader use @graphitation/ts-transform-graphql-js-tag

const { getTransformer } = require("@graphitation/ts-transform-graphql-js-tag");


{
  test: /\.tsx?$/,
  loader: "ts-loader",
  options: {
    getCustomTransformers: () => ({
      before: [
        getTransformer({
          graphqlTagModuleExport: "graphql",
          graphqlTagModule: "@nova/react",
        }),
      ],
    }),
  },
},

For babel-loader (make sure template tags aren't stripped out by typescript by setting target to be at least ES6) use babel-plugin-graphql-tag

{
  loader: "babel-loader",
  options: {
    plugins: [
      [
        "babel-plugin-graphql-tag",
        {
            strip: true,
            importSources: ["@nova/react"],
            gqlTagIdentifiers: ["graphql"],
        },
      ],
    ],
  },
},

Eventing

Nova eventing exposes a clearly contracted, component driven way to surface actions that occur within in the boundaries of a component. These events are published in an independent package so that they can be easily consumed by code that is outside of the component tree.

Primary Use Cases for Events

• Bubbling a button click that should perform some sort of navigation or external action, like opening a modal on host app side.
• Bubbling an internal action that needs to be logged.

Eventing Contract

Eventing is primarily a contract between the component owner and host apps. The Event data object should contain all the appropriate context to allow the host apps to appropriately handle the event.

If the host app needs additional data to perform an action, this should be discussed with the component team to add an event or extend the data sent.

Eventing methods

Nova eventing provides two methods to propagate events:

• bubble - to propagate events that are happening as a result of user interaction and have React event associated with them
• generateEvent - to generate events that are not related to user interactions, but triggered programmatically (like informing host app that component completed rendering)

The guidance is to always use bubble as that way event automatically gets additional metadata. generateEvent should be used only when there is no user interaction involved.

Basic example

import { NovaEventingProvider, reactEventMapper } from "@nova/react";

const eventHandler = (eventWrapper: EventWrapper) => {
  if (eventWrapper.event.eventType === "showProfile") {
    // trigger some action to show profile
  }
  if (eventWrapper.originator === "MyComponent") {
    return handleEventsForMyComponent(eventWrapper);
  }
};

const AppEventingProvider = ({ children }: { children: React.ReactNode }) => {
  return (
    <NovaEventingProvider
      bubble={eventHandler}
      reactEventMapper={
        reactEventMapper
      } /* you can also provide your own implementation of mapper */
    >
      {children}
    </NovaEventingProvider>
  );
};

Then in some low level component

import { useNovaEventing } from "@nova/react";

const MyComponent = () => {
  const eventing = useNovaEventing();

  React.useEffect(() => {
    // use `generateEvent` for events not related to user interactions
    eventing.generateEvent({
      event: {
        eventType: "onRenderComplete",
        originator: "MyComponent",
      },
    });
  }, [eventing]);

  const handleClick = (event: React.SyntheticEvent) => {
    // use bubble for events triggered by user
    eventing.bubble({
      reactEvent: event,
      event: {
        eventType: "selectProfile",
        originator: "MyComponent",
        data: () => ({
          userId: "123",
        }),
      },
    });
  };

  return <button onClick={handleClick}>Select profile</button>;
};

Intercepting events

As NovaEventingProvider is usually defined at the top level of the app, you may want to intercept events, which are more specific to your component and can be handled on lower level. This is not encouraged as it makes the handling not reusable by other component but if you are sure the event is specific and you want to handle it lower (like passing some arguments to your host app wrapper), you can use NovaEventingInterceptor:

const MyComponentWrapper = () => {
  const [userId, setUserId] = useState<string | null>(null);

  const defaultInterceptor = (eventWrapper: EventWrapper) => {
    if (
      eventWrapper.event.originator === "MyComponent" &&
      eventWrapper.event.eventType === "selectProfile"
    ) {
      const data = eventWrapper.event.data();
      setUserId(data.userId);
      return Promise.resolve(undefined);
    } else {
      return Promise.resolve(eventWrapper);
    }
  };

  return (
    <NovaEventingInterceptor intercept={defaultInterceptor}>
      {userId && <Profile userId={userId} />}
      <ComponentThatRenderMyComponentSomewhereInside />
    </NovaEventingInterceptor>
  );
};

The NovaEventingInterceptor will intercept the event and if you can check it's properties to decide if is should be acted upon. If from intercept promise resolving to undefined is returned the event will not be passed to eventing higher up the tree. However, if to process the event further, one should return a promise resolving to the eventWrapper object. That also gives a possibility to alter the event and still pass it further up.

You can nest as many interceptors as you need to either handle or pass events further up.

Localization

Note for this to work you will need to use the Microsoft internal fork of the Relay compiler that includes the added functionality.

Localized strings are provided to components through GraphQL fragments. For simple strings these will be typed as string and can be used directly. For strings that include placeholders the Relay compiler will type them as StringWithPlaceholders from @nova/react.

This is an opaque type that includes the placeholders required by the string. You can use the format function provided by useFormat from @nova/react to format the string with the required values.

Defining a localized string

You can define a localized string in your GraphQL schema by using the @localizedString directive. This directive takes a text argument which is the string with placeholders and a comment argument which is a description of the string.

Simple string

type ViewData {
  greeting: String! @localizedString(
    text: "Welcome!",
    comment: "Greeting to the user",
  )
}

In typescript this will be typed as string.

type ViewData = {
  greeting: string;
};

String with placeholders

In the case of a string with placeholders you will also need to provide a placeholders argument which is a list of objects with a name and comment field.

type ViewData {
  greeting: String! @localizedString(
    text: "Hello, {name}",
    comment: "Greeting to the user",
    placeholders: [
      {
        name: "name",
        comment: "The name of the user"
      }
    ]
  )
}

In typescript this will be typed as StringWithPlaceholders.

type ViewData = {
  greeting: StringWithPlaceholders<{ name: string; }>;
};

Consuming a localized string

When consuming a localized string you can use it directly if it is a simple string.

import { useFragment } from "@nova/react";

const MyComponent = ({ viewData }) => {
  const { greeting } = useFragment(
    graphql`
      fragment MyComponent_viewData on ViewData {
        greeting
      }
    `
    viewData
  )

  return <div>{greeting}</div>;
};

Consuming a localized string with placeholders

When consuming a localized string with placeholders you will need to use the format function provided by useFormat from @nova/react. This function takes the string and an object with the values for the placeholders.

import { useFragment, useFormat } from "@nova/react";

const MyComponent = ({ viewData }) => {
  const { greeting } = useFragment(
    graphql`
      fragment MyComponent_viewData on ViewData {
        greeting
      }
    `
    viewData
  )

  const format = useFormat();

  return <div>{format(greeting, { name })}</div>;
};

Providing the useFormat hook implementation

The useFormat hook implementation is provided through the NovaLocalizationProvider component from @nova/react. This component should be placed at the top level of your application and will provide the implementation to all components that use the useFormat hook.

This ensures that each host application can provide their own implementation of the useFormat hook.

import { NovaLocalizationProvider, type NovaLocalization } from "@nova/react";

const localization: NovaLocalization = {
  useFormat: () => {
    // Your implementation goes here
    // You can use other hooks here.
    
    // For example useTranslation from i18next
    const { t } = useTranslation();

    return (string: string, values: Record<string, string>) => t(string, values);
  }
}

const App = () => {
  return (
    <NovaLocalizationProvider localization={localization}>
      <OtherComponents />
    </NovaLocalizationProvider>
  );
};