fate is a modern data client for React and tRPC inspired by Relay and GraphQL. It combines view composition, normalized caching, data masking, Async React features, and tRPC's type safety.

Features

View Composition: Components declare their data requirements using co-located "views". Views are composed into a single request per screen, minimizing network requests and eliminating waterfalls.
Normalized Cache: fate maintains a normalized cache for all fetched data. This enables efficient data updates through actions and mutations and avoids stale or duplicated data.
Data Masking & Strict Selection: fate enforces strict data selection for each view, and masks (hides) data that components did not request. This prevents accidental coupling between components and reduces overfetching.
Async React: fate uses modern Async React features like Actions, Suspense, and use to support concurrent rendering and enable a seamless user experience.
Lists & Pagination: fate provides built-in support for connection-style lists with cursor-based pagination, making it easy to implement infinite scrolling and "load-more" functionality.
Optimistic Updates: fate supports declarative optimistic updates for mutations, allowing the UI to update immediately while the server request is in-flight. If the request fails, the cache and its associated views are rolled back to their previous state.
AI-Ready: fate's minimal, predictable API and explicit data selection enable local reasoning, enabling humans and AI tools to generate stable, type-safe data-fetching code.

A modern data client for React & tRPC

fate is designed to make data fetching and state management in React applications more composable, declarative, and predictable. The framework has a minimal API, no DSL, and no magic—it's just JavaScript.

GraphQL and Relay introduced several novel ideas: fragments co‑located with components, a normalized cache keyed by global identifiers, and a compiler that hoists fragments into a single network request. These innovations made it possible to build large applications where data requirements are modular and self‑contained.

Nakazawa Tech builds apps and games primarily with GraphQL and Relay. We advocate for these technologies in talks and provide templates (server, client) to help developers get started quickly.

However, GraphQL comes with its own type system and query language. If you are already using tRPC or another type‑safe RPC framework, it's a significant investment to adopt and implement GraphQL on the backend. This investment often prevents teams from adopting Relay on the frontend.

Many React data frameworks lack Relay's ergonomics, especially fragment composition, co-located data requirements, predictable caching, and deep integration with modern React features. Optimistic updates usually require manually managing keys and imperative data updates, which is error-prone and tedious.

fate takes the great ideas from Relay and puts them on top of tRPC. You get the best of both worlds: type safety between the client and server, and GraphQL-like ergonomics for data fetching. Using fate usually looks like this:

export const PostView = view<Post>()({
  author: UserView,
  content: true,
  id: true,
  title: true,
});

export const PostCard = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);

  return (
    <Card>
      <h2>{post.title}</h2>
      <p>{post.content}</p>
      <UserCard user={post.author} />
    </Card>
  );
};

Learn more about fate's core concepts or get started with a ready-made template.

Getting Started

Template

Get started with a ready-made template quickly:

::: code-group

npx giget@latest gh:nkzw-tech/fate-template

pnpx giget@latest gh:nkzw-tech/fate-template

yarn dlx giget@latest gh:nkzw-tech/fate-template

:::

fate-template comes with a simple tRPC backend and a React frontend using fate. It features modern tools to deliver an incredibly fast development experience. Follow its README.md to get started.

Manual Installation

fate requires React 19.2+. For your client you need to install react-fate:

::: code-group

npm add react-fate

pnpm add react-fate

yarn add react-fate

:::

And for your server, install the core @nkzw/fate package:

::: code-group

npm add @nkzw/fate

pnpm add @nkzw/fate

yarn add @nkzw/fate

:::

Warning

fate is currently in alpha and not production ready. If something doesn't work for you, please open a pull request.

If you'd like to try the example app in GitHub Codespaces, click the button below:

Core Concepts

fate has a minimal API surface and is aimed at reducing data fetching complexity.

Thinking in Views

In fate, each component declares the data it needs using views. Views are composed upward through the component tree until they reach a root, where the actual request is made. fate fetches all required data in a single request. React Suspense manages loading states, and any data-fetching errors naturally bubble up to React error boundaries. This eliminates the need for imperative loading logic or manual error handling.

Traditionally, React apps are built with components and hooks. fate introduces a third primitive: views – a declarative way for components to express their data requirements. An app built with fate looks more like this:

Tree

With fate, you no longer worry about when to fetch data, how to coordinate loading states, or how to handle errors imperatively. You avoid overfetching, stop passing unnecessary data down the tree, and eliminate boilerplate types created solely for passing server data to child components.

Note

Views in fate are what fragments are in GraphQL.

Views

Defining Views

Let's start by defining a simple view for a blog's Post component. fate requires you to explicitly "select" each field that you plan to use in your components. Here is how you can define a view for a Post entity that has title and content fields:

import { view } from 'react-fate';

type Post = {
  content: string;
  id: string;
  title: string;
};

export const PostView = view<Post>()({
  content: true,
  id: true,
  title: true,
});

Fields are selected by setting them to true in the view definition. This tells fate that these fields should be fetched from the server and made available to components that use this view.

Note

The Post type above is an example. In a real application, this type is defined on the server and imported into your client code.

Resolving a View with `useView`

Now we can use the view that we defined in a PostCard React component to resolve the data against a reference of an individual Post:

import { useView, ViewRef } from 'react-fate';

export const PostCard = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);

  return (
    <Card>
      <h2>{post.title}</h2>
      <p>{post.content}</p>
    </Card>
  );
};

A ViewRef is a reference to a concrete object of a specific type, for example a Post with id 7. It contains the unique ID of the object, the type name (as __typename) and some fate-specific metadata. fate creates and manages these references for you, and you can pass them around your components as needed.

Components using useView listen to changes for all selected fields. When data changes, fate re-renders all of the fields that depend on that data. For example, if the title of the Post changes, the PostCard component re-renders with new data. However, if a different field such as likes that isn't selected in PostView changes, the PostCard component will not re-render.

Fetching Data with `useRequest`

Now that we defined our view and component, we fetch the data from the server using the useRequest hook from fate. This hook allows us to declare what data we need for a specific screen or component tree. At the root of our app, we can request a list of posts like this:

import { useRequest } from 'react-fate';
import { PostCard, PostView } from './PostCard.tsx';

export function App() {
  const { posts } = useRequest({ posts: { list: PostView } });

  return posts.map((post) => <PostCard key={post.id} post={post} />);
}

Learn more about useRequest in the Requests Guide.

Composing Views

In the above example we are defining a single view for a Post. One of fate's core strengths is view composition. Let's say we want to show the author's name along with the post. A simple way to do this is by adding an author field to the PostView with a concrete selection:

import { Suspense } from 'react';
import { useView, ViewRef } from 'react-fate';

export const PostView = view<Post>()({
  author: {
    id: true,
    name: true,
  },
  content: true,
  id: true,
  title: true,
});

const PostCard = ({ postRef }: { postRef: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);
  return (
    <Card>
      <h2>{post.title}</h2>
      <p>by {post.author.name}</p>
      <p>{post.content}</p>
    </Card>
  );
};

This code fetches the author associated with the Post and makes it available to the PostCard component. However, this approach has some downsides:

The author selection is tightly coupled to the PostView. If we want to use the author's data in another component, we would need to duplicate the field selection.
If the author has more fields that we want to use in other components, we would need to add them to the PostView, leading to overfetching.
We cannot reuse the author field selection in other views or components.

In fate, views are composable and reusable. Instead of inlining the selection, we can define a UserView and compose it into the PostView like this:

import type { Post, User } from '@your-org/server/trpc/views';
import { view } from 'react-fate';

export const UserView = view<User>()({
  id: true,
  name: true,
  profilePicture: true,
});

export const PostView = view<Post>()({
  author: UserView,
  content: true,
  id: true,
  title: true,
});

Now we can create a separate UserCard component that uses our UserView:

import { useView, ViewRef } from 'react-fate';

export const UserCard = ({ user: userRef }: { user: ViewRef<'User'> }) => {
  const user = useView(UserView, userRef);

  return (
    <div>
      <img src={user.profilePicture} alt={user.name} />
      <p>{user.name}</p>
    </div>
  );
};

And update PostCard to use our UserCard component:

import { UserCard } from './UserCard.tsx';

export const PostCard = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);

  return (
    <Card>
      <h2>{post.title}</h2>
      <UserCard user={post.author} />
      <p>{post.content}</p>
    </Card>
  );
};

View Spreads

When building complex UIs, you will often build multiple components that share the same data requirements. In fate, you can use view spreads to compose such views together. This is similar to GraphQL fragment spreads, but works with plain JavaScript objects.

Let's assume we want to fetch and display additional information about the author in the PostCard, such as their bio. Instead of directly assigning our UserView to the author field, we can instead spread it and add the bio field:

export const PostView = view<Post>()({
  author: {
    ...UserView,
    bio: true,
  },
  content: true,
  id: true,
  title: true,
});

Now the PostCard component can access the bio field of the author:

export const PostCard = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);

  return (
    <Card>
      <h2>{post.title}</h2>
      <UserCard author={post.author} />
      {/* Accessing the bio field */}
      <p>{post.author.bio}</p>
      <p>{post.content}</p>
    </Card>
  );
};

We can also spread multiple views together. For example, if we have another view called UserStatsView that selects some statistics about the user, we can include it in the PostView like this:

export const UserStatsView = view<User>()({
  followerCount: true,
  postCount: true,
});

export const PostView = view<Post>()({
  author: {
    ...UserView,
    ...UserStatsView,
    bio: true,
  },
  content: true,
  id: true,
  title: true,
});

Views are opaque objects. Even if you select the same field multiple times through different views, the composed object won't have conflicting fields or result in TypeScript errors. fate automatically deduplicates fields during runtime and ensures that each field is only fetched once.

`useView` and Suspense

We learned that useRequest is responsible for fetching data from the server and useView is used for reading data from the cache. In some situations data may not be available in the cache and useView might need to suspend the component to fetch only the missing data. Once that data is fetched and written to the cache, the component resumes rendering.

Tip: You can test this behavior in development mode with Fast Refresh (HMR) enabled in your bundler. When you edit the selection of a view, components using that view will suspend, fetch the missing data, and then resume rendering.

Type Safety and Data Masking

fate provides guarantees through TypeScript and during runtime that prevent you from accessing data that wasn't selected in a component. This ensures that you declare all the data dependencies at the right level in your component tree, and prevents accidental coupling between components.

In the below example, we forgot to select the content of a Post. As a result, type-checks fail and the content field is undefined during runtime:

const PostView = view<Post>()({
  id: true,
  title: true,
  // `content: true` is omitted.
});

const PostCard = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);

  return (
    <Card>
      <h2>{post.title}</h2>
      {/* TypeScript errors here, and `post.content` is undefined during runtime */}
      <p>{post.content}</p>
    </Card>
  );
};

Views can only be resolved against refs that include that view directly or via view spreads. If a component tries to resolve a view against a ref that isn't linked, it will throw an error during runtime:

const PostDetailView = view<Post>()({
  content: true,
});

const AnotherPostView = view<Post>()({
  content: true,
});

const PostView = view<Post>()({
  id: true,
  title: true,
  ...AnotherPostView,
});

const PostCard = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  const post = useView(PostView, postRef);
  return <PostDetail post={post} />;
};

const PostDetail = ({ post: postRef }: { post: ViewRef<'Post'> }) => {
  // This throws because the post reference passed into this component
  // is of type `AnotherPostView`, not `PostDetailView`.
  const post = useView(PostDetailView, postRef);
};

ViewRefs carry a set of view names they can resolve. useView throws if a ref does not include the required view.

Requests

Requesting Lists

The useRequest hook can be used to declare our data needs for a specific screen or component tree. At the root of our app, we can request a list of posts like this:

import { useRequest } from 'react-fate';
import { PostCard, PostView } from './PostCard.tsx';

export function App() {
  const { posts } = useRequest({ posts: { list: PostView } });
  return posts.map((post) => <PostCard key={post.id} post={post} />);
}

This component suspends or throws errors, which bubble up to the nearest error boundary. Wrap your component tree with ErrorBoundary and Suspense components to show error and loading states:

<ErrorBoundary FallbackComponent={ErrorComponent}>
  <Suspense fallback={<div>Loading…</div>}>
    <App />
  </Suspense>
</ErrorBoundary>

Note

useRequest might issue multiple requests which are automatically batched together by tRPC's HTTP Batch Link into a single network request.

Requesting Objects by ID

If you want to fetch data for a single object instead of a list, you can specify the id and the associated view like this:

const { post } = useRequest({
  post: { id: '12', view: PostView },
});

If you want to fetch multiple objects by their IDs, you can use the ids field:

const { posts } = useRequest({
  posts: { ids: ['6', '7'], view: PostView },
});

Other Types of Requests

For any other queries, pass only the type and view:

const { viewer } = useRequest({
  viewer: { view: UserView },
});

Request Arguments

You can pass arguments to useRequest calls. This is useful for pagination, filtering, or sorting. For example, to fetch the first 10 posts, you can do the following:

const { posts } = useRequest({
  posts: {
    args: { first: 10 },
    list: PostView,
  },
});

Request Modes

useRequest supports different request modes to control caching and data freshness. The available modes are:

cache-first (default): Returns data from the cache if available, otherwise fetches from the network.
stale-while-revalidate: Returns data from the cache and simultaneously fetches fresh data from the network.
network-only: Always fetches data from the network, bypassing the cache.

You can pass the request mode as an option to useRequest:

const { posts } = useRequest(
  {
    posts: { list: PostView },
  },
  {
    mode: 'stale-while-revalidate',
  },
);

List Views

Pagination with `useListView`

You can wrap a list of references using useListView to enable connection-style lists with pagination support.

For example, you can define a CommentView and reuse it inside of a CommentConnectionView:

import { useListView, ViewRef } from 'react-fate';

const CommentView = view<Comment>()({
  content: true,
  id: true,
});

const CommentConnectionView = {
  args: { first: 10 },
  items: {
    node: CommentView,
  },
};

const PostView = view<Post>()({
  comments: CommentConnectionView,
});

Now you can apply the useListView hook inside of your PostCard component to read the list of comments and load more comments when needed:

export function PostCard({
  detail,
  post: postRef,
}: {
  detail?: boolean;
  post: ViewRef<'Post'>;
}) {
  const post = useView(PostView, postRef);
  const [comments, loadNext] = useListView(
    CommentConnectionView,
    post.comments,
  );

  return (
    <div>
      {comments.map(({ node }) => (
        <CommentCard comment={node} key={node.id} post={post} />
      ))}
      {loadNext ? (
        <Button onClick={loadNext} variant="ghost">
          Load more comments
        </Button>
      ) : null}
    </div>
  );
}

If loadNext is undefined, it means there are no more comments to load. If you want to instead load previous comments, you can use the third argument returned by useListView, which is loadPrevious. Similarly, if there are no previous comments to load, loadPrevious will be undefined.

Actions

fate does not provide hooks for mutations like traditional data fetching libraries do. Instead, mutations are exposed in two ways:

fate.actions for use with useActionState and React Actions.
fate.mutations for traditional imperative mutation calls.

Mutations in your tRPC backend are made available as actions and mutations by fate's generated client.

Let's assume that our Post entity has a tRPC mutation for liking a post called post.like. A LikeButton component using fate Actions and an async component library could then look like this:

import { useActionState } from 'react';
import { useFateClient } from 'react-fate';

const LikeButton = ({ post }: { post: { id: string; likes: number } }) => {
  const fate = useFateClient();
  const [result, like] = useActionState(fate.actions.post.like, null);

  return (
    <Button action={() => like({ input: { id: post.id } })}>
      {result?.error ? 'Oops!' : 'Like'}
    </Button>
  );
};

If you are not using an async component library, you can use React's useTransition to start the action in a transition:

const LikeButton = ({ post }: { post: { id: string; likes: number } }) => {
  const fate = useFateClient();
  const [, startTransition] = useTransition();
  const [result, like, isPending] = useActionState(
    fate.actions.post.like,
    null,
  );

  return (
    <button
      disabled={isPending}
      onClick={() => {
        startTransition(() =>
          like({
            input: { id: post.id },
          }),
        );
      }}
    >
      {result?.error ? 'Oops!' : 'Like'}
    </button>
  );
};

By using useActionState, fate Actions integrate with Suspense and concurrent rendering.

Optimistic Updates

fate Actions support optimistic updates out of the box. For example, to update the post's like count optimistically, you can pass an optimistic object to the action call. This will immediately update the cache with the new like count and re-render all views that select the likes field:

like({
  input: { id: post.id },
  optimistic: { likes: post.likes + 1 },
});

When data changes through optimistic updates or otherwise, fate only re-renders the views that select the changed fields. In the above example, only views that select the likes field will re-render. If a view only selects the title field, it won't re-render when the likes field changes.

If a mutation fails, the cache will be rolled back to its previous state and any views depending on the mutated data will be updated.

Inserting New Objects

When a mutation inserts a new object, you can provide an optimistic object with a temporary ID to represent the new object in the cache until the server responds with the actual ID. For example, to add a new comment to a post optimistically, you can do the following:

const content = 'New Comment text';
addComment({
  input: { content, postId: post.id },
  optimistic: {
    author: { id: user.id, name: user.name },
    content,
    id: `optimistic:${Date.now().toString(36)}`,
    post: { commentCount: post.commentCount + 1, id: post.id },
  },
});

Selecting a View with Actions

Mutations may change data that is not directly specified in the mutation result. For example, adding a comment increases the post's comment count. For such cases, you can provide a view to an action that specifies which fields to fetch as part of the mutation:

addComment({
  input: { content: 'New Comment text', postId: post.id },
  view: view<Comment>()({
    ...CommentView,
    post: { commentCount: true },
  }),
});

The server will return the selected fields and fate updates the cache and re-renders all views that depend on the changed data. The action result contains the newly added comment with the selected fields:

const [result, addComment] = useActionState(fate.actions.comment.add, null);

const newComment = result?.result;
if (newComment) {
  // All the fields selected in the view are available on `newComment`:
  console.log(newComment.post.commentCount);
}

Mutations

fate Actions are the recommended way to execute server mutations in React components. However, there are cases where you might want to call mutations imperatively, outside of React components, or without waiting for previous actions to finish like useActionState does. For such cases, you can use fate.mutations to call mutations imperatively:

const result = await fate.mutations.comment.add({
  input: { content, postId: post.id },
});

You can call mutations from anywhere, and without waiting for previous mutations to finish. The mutation API matches the API of fate Actions, including optimistic updates and view selection. With mutations, you'll need to handle loading states and errors manually, and the result is returned as a promise.

Mutation Server Implementation

fate Actions & Mutations are backed by regular tRPC mutations on the server. Here is an example implementation of the like mutation in the postRouter.

import { z } from 'zod';
import { connectionArgs, createResolver } from '@nkzw/fate/server';
import { procedure, router } from '../init.ts';
import { postDataView, PostItem } from '../views.ts';

export const postRouter = router({
  like: procedure
    .input(
      z.object({
        args: connectionArgs,
        id: z.string().min(1, 'Post id is required.'),
        select: z.array(z.string()),
      }),
    )
    .mutation(async ({ ctx, input }) => {
      const { resolve, select } = createResolver({
        ...input,
        ctx,
        view: postDataView,
      });

      return resolve(
        await ctx.prisma.post.update({
          data: {
            likes: {
              increment: 1,
            },
          },
          select,
          where: { id: input.id },
        } as PostUpdateArgs),
      );
    }),
});

See the Server Integration section for more details on how to integrate tRPC routers with fate.

Action & Mutation Error Handling

fate Actions & Mutations separate error handling into two scopes: "call site" and "boundary". Call site errors are expected to be handled at the location where the action or mutation is called. Boundary errors are unexpected errors that should be handled by a higher-level error boundary.

If your server returns a NOT_FOUND error with code 404, the result of an Action or Mutation will contain an error object that you can handle at the call site:

const [result] = useActionState(fate.actions.post.delete, null);

if (result?.error) {
  if (result.error.code === 'NOT_FOUND') {
    // Handle not found error at call site.
  } else {
    // Handle other *expected* errors.
  }
}

However, if an INTERNAL_SERVER_ERROR error with code 500 occurs, it will be thrown and can be caught by the nearest React error boundary:

<ErrorBoundary FallbackComponent={ErrorComponent}>
  <Suspense fallback={<div>Loading…</div>}>
    <PostPage postId={postId} />
  </Suspense>
</ErrorBoundary>

You can find the error classification behavior in mutation.ts.

Deleting Records

When you want to delete a record using fate Actions, you can pass a delete: true flag to the action call. This flag removes the object from the cache and re-renders all views that depend on the deleted data:

const [result, deleteAction] = useActionState(fate.actions.post.delete, null);

deleteAction({
  input: { id: post.id },
  delete: true,
});

Resetting Action State

When using useActionState, the result of the action is cached until the component using the action is unmounted. When a mutation fails with an error, you might want to clear the error state without invoking the action again. fate Actions take a 'reset' token to reset the action state:

const [result, like] = useActionState(fate.actions.post.like, null);

useEffect(() => {
  if (result?.error) {
    // Reset the action state after 3 seconds.
    const timeout = setTimeout(
      () => startTransition(() => like('reset')),
      3000,
    );
    return () => clearTimeout(timeout);
  }
}, [like, result]);

Controlling List Insertion Behavior

When inserting new objects into lists, the default behavior is to append the new object to the list. You can provide an insert option with before, after or none values to customize this behavior and specify where the new object should be inserted in the list:

addComment({
  input: { content: 'New Comment text', postId: post.id },
  insert: 'before', // Insert the new comment at the beginning of the list.
});

Or, use the none option if you want to ignore inserting the new object into any lists:

addComment({
  input: { content: 'New Comment text', postId: post.id },
  insert: 'none', // Do not insert the new comment into any lists.
});

Server Integration

Until now, we have focused on the client-side API of fate. You'll need a tRPC backend that follows some conventions so you can generate a typed client using fate's CLI. At the moment fate is designed to work with tRPC and Prisma, but the framework is not coupled to any particular ORM or database, it's just what we are starting with.

Conventions & Object Identity

fate expects that data is served by a tRPC backend that follows these conventions:

A byId query for each data type to fetch individual objects by their unique identifier (id).
A list query for fetching lists of objects with support for pagination.

Objects are identified by their ID and type name (__typename, e.g. Post, User), and stored by __typename:id (e.g. "Post:123") in the client cache. fate keeps list orderings under stable keys derived from the backend procedure and args. Relations are stored as IDs and returned to components as ViewRef tokens.

fate's type definitions might seem verbose at first glance. However, with fate's minimal API surface, AI tools can easily generate this code for you. For example, fate has a minimal CLI that generates types for the client, but you can also let your LLM write it by hand if you prefer.

Note

You can adopt fate incrementally in an existing tRPC codebase without changing your existing schema by adding these queries alongside your existing procedures.

Data Views

To continue with our client example, let's assume we have a post.ts file with a tRPC router that exposes a byId query for selecting objects by id, and a root list query to fetch a list of posts.

Since clients can send arbitrary selection objects to the server, we need to implement a way to translate these selection objects into database queries without exposing raw database queries and private data to the client. On the client, we define views to select fields on each type. We can do the same on the server using fate data views and the dataView function from @nkzw/fate/server.

Create a views.ts file next to your root tRPC router that exports the data views for each type. Here is how you can define a User data view for Prisma's User model:

import { dataView, type Entity } from '@nkzw/fate/server';
import type { User as PrismaUser } from '../prisma/prisma-client/client.ts';

export const userDataView = dataView<PrismaUser>('User')({
  id: true,
  name: true,
  username: true,
});

export type User = Entity<typeof userDataView, 'User'>;

Note: Currently, fate provides helpers to integrate with Prisma, but the framework is not coupled to any particular ORM or database. We hope to provide more direct integrations in the future, and are always open to contributions.

tRPC Router Implementation

We can apply the above data view in our tRPC router and resolve the client's selection against it using createResolver. Here is an example implementation of the byId query for the User type which allows fetching multiple users by id:

import { byIdInput, createResolver } from '@nkzw/fate/server';
import { z } from 'zod';
import type { UserFindManyArgs } from '../../prisma/prisma-client/models.ts';
import { procedure, router } from '../init.ts';
import { userDataView } from '../views.ts';

export const userRouter = router({
  byId: procedure.input(byIdInput).query(async ({ ctx, input }) => {
    const { resolveMany, select } = createResolver({
      ...input,
      ctx,
      view: userDataView,
    });

    const users = await ctx.prisma.user.findMany({
      select: select,
      where: { id: { in: input.ids } },
    } as UserFindManyArgs);

    return await resolveMany(users);
  }),
});

Now that we apply userDataView to the byId query, the server limits the selection to the fields defined in the data view, keeping private fields hidden from the client, and providing type safety for client views:

const UserData = view<User>()({
  // Type-error + ignored during runtime.
  password: true,
});

tRPC List Implementation

To implement the list query for fetching a paginated list of posts, we can use fate's createConnectionProcedure helper. This helper simplifies the implementation of pagination. Here is an example implementation of the postRouter with a list query:

import { createResolver } from '@nkzw/fate/server';
import type { PostFindManyArgs } from '../../prisma/prisma-client/models.ts';
import { createConnectionProcedure } from '../connection.ts';
import { router } from '../init.ts';
import { postDataView } from '../views.ts';

export const postRouter = router({
  list: createConnectionProcedure({
    query: async ({ ctx, cursor, direction, input, skip, take }) => {
      const { resolveMany, select } = createResolver({
        ...input,
        ctx,
        view: postDataView,
      });
      const findOptions: PostFindManyArgs = {
        orderBy: { createdAt: 'desc' },
        select,
        take: direction === 'forward' ? take : -take,
      };

      if (cursor) {
        findOptions.cursor = { id: cursor };
        findOptions.skip = skip;
      }

      const items = await ctx.prisma.post.findMany(findOptions);
      return resolveMany(direction === 'forward' ? items : items.reverse());
    },
  }),
});

Data View Composition

Similar to client-side views, data views can be composed of other data views:

export const postDataView = dataView<PostItem>('Post')({
  author: userDataView,
  content: true,
  id: true,
  title: true,
});

Data View Lists

Use the list helper to define list fields:

import { list } from '@nkzw/fate/server';

export const commentDataView = dataView<CommentItem>('Comment')({
  content: true,
  id: true,
});

export const postDataView = dataView<PostItem>('Post')({
  author: userDataView,
  comments: list(commentDataView),
});

We can define extra root-level lists and queries by exporting a Root object from our views.ts file using the same view syntax as everywhere else:

export const Root = {
  categories: list(categoryDataView),
  commentSearch: { procedure: 'search', view: list(commentDataView) },
  events: list(eventDataView),
  posts: list(postDataView),
  viewer: userDataView,
};

Entries that wrap their view in list(...) are treated as list resolvers and use the procedure name when calling the corresponding router procedure, defaulting to list. If you omit list(...), fate treats the entry as a standard query and uses the view type name to infer the router name.

For the above Root definitions, you can make the following requests using useRequest:

const query = 'Apple';

const { posts, categories, viewer } = useRequest({
  // Explicit Root queries:
  categories: { list: categoryView },
  commentSearch: { args: { query }, list: commentView },
  events: { list: eventView },
  posts: { list: postView },
  viewer: { view: userView },

  // Queries by id, if those entities have a `byId` query defined:
  post: { id: '12', view: postView },
  comment: { ids: ['6', '7'], view: commentView },
});

Data View Resolvers

fate data views support resolvers for computed fields. If we want to add a commentCount field to our Post data view, we can use the resolver helper that defines a Prisma selection for the database query together with a resolve function:

export const postDataView = dataView<PostItem>('Post')({
  author: userDataView,
  commentCount: resolver<PostItem, number>({
    resolve: ({ _count }) => _count?.comments ?? 0,
    select: () => ({
      _count: { select: { comments: true } },
    }),
  }),
  comments: list(commentDataView),
  id: true,
});

This definition makes the commentCount field available to your client-side views.

Authorization in Resolvers

You might want to restrict access to certain fields based on the current user or other contextual information. You can do this by adding an authorize function to your resolver definition:

export const userDataView = dataView<UserItem>('User')({
  email: resolver<UserItem, string | null, { sessionUser: string }>({
    authorize: ({ id }, context) => context?.sessionUserId === id,
    resolve: ({ email }) => email,
  }),
  id: true,
});

Generating a typed client

Now that we have defined our client views and our tRPC server, we need to connect them with some glue code. We recommend using fate's CLI for convenience.

First, make sure our tRPC router.ts file exports the appRouter object, AppRouter type and all the views we have defined:

import { router } from './init.ts';
import { postRouter } from './routers/post.ts';
import { userRouter } from './routers/user.ts';

export const appRouter = router({
  post: postRouter,
  user: userRouter,
});

export type AppRouter = typeof appRouter;

export * from './views.ts';

Note: We try to keep magic to a minimum and you can handwrite the generated client if you prefer.

pnpm fate generate @your-org/server/trpc/router.ts client/src/fate.ts

Note: fate uses the specified server module name to extract the server types it needs and uses the same module name to import the views into the generated client. Make sure that the module is available both at the root where you are running the CLI and in the client package.

Creating a fate Client

Now that we have generated the client types, all that remains is creating an instance of the fate client, and using it in our React app using the FateClient context provider:

import { httpBatchLink } from '@trpc/client';
import { FateClient } from 'react-fate';
import { createFateClient } from './fate.ts';

export function App() {
  const fate = useMemo(
    () =>
      createFateClient({
        links: [
          httpBatchLink({
            fetch: (input, init) =>
              fetch(input, {
                ...init,
                credentials: 'include',
              }),
            url: `${env('SERVER_URL')}/trpc`,
          }),
        ],
      }),
    [],
  );
  return <FateClient client={fate}>{/* Components go here */}</FateClient>;
}

And you are all set. Happy building!

Frequently Asked Questions

Is this serious software?

In an alternate reality, fate can be described like this:

fate is an ambitious React data library that tries to blend Relay-style ideas with tRPC, held together by equal parts vision and vibes. It aims to fix problems you definitely wouldn't have if you enjoy writing the same fetch logic in three different places with imperative loading state and error handling. fate promises predictable data flow, minimal APIs, and "no magic", though you may occasionally suspect otherwise.

fate is almost certainly worse than actual sync engines, but will hopefully be better than existing React data-fetching libraries eventually. Use it if you have a high tolerance for pain and want to help shape the future of data fetching in React.

Is fate better than Relay?

Absolutely not.

Is fate better than using GraphQL?

Probably. One day. Maybe.

How was fate built?

Note

80% of fate's code was written by OpenAI's Codex – four versions per task, carefully curated by a human. The remaining 20% was written by @cnakazawa. You get to decide which parts are the good ones! The docs were 100% written by a human.

If you contribute to fate, we require you to disclose your use of AI tools.

Future

fate is not complete yet. The library lacks core features such as garbage collection, a compiler to extract view definitions statically ahead of time, and there is too much backend boilerplate. The current implementation of fate is not tied to tRPC or Prisma, those are just the ones we are starting with. We welcome contributions and ideas to improve fate. Here are some features we'd like to add:

Support for Drizzle
Support backends other than tRPC
Persistent storage for offline support
Implement garbage collection for the cache
Better code generation and less type repetition
Support for live views and real-time updates via useLiveView and SSE

Acknowledgements

Relay, Isograph & GraphQL for inspiration
Ricky Hanlon for guidance on Async React
Anthony Powell for testing fate and providing feedback

fate was created by @cnakazawa and is maintained by Nakazawa Tech.

Features

A modern data client for React & tRPC

Getting Started

Template

Manual Installation

Core Concepts

Thinking in Views

Views

Defining Views

Resolving a View with useView

Fetching Data with useRequest

Composing Views

View Spreads

useView and Suspense

Type Safety and Data Masking

Requests

Requesting Lists

Requesting Objects by ID

Other Types of Requests

Request Arguments

Request Modes

List Views

Pagination with useListView

Actions

Optimistic Updates

Inserting New Objects

Selecting a View with Actions

Mutations

Mutation Server Implementation

Action & Mutation Error Handling

Deleting Records

Resetting Action State

Controlling List Insertion Behavior

Server Integration

Conventions & Object Identity

Data Views

tRPC Router Implementation

tRPC List Implementation

Data View Composition

Data View Lists

Data View Resolvers

Authorization in Resolvers

Generating a typed client

Creating a fate Client

Frequently Asked Questions

Is this serious software?

Is fate better than Relay?

Is fate better than using GraphQL?

How was fate built?

Future

Acknowledgements

Resolving a View with `useView`

Fetching Data with `useRequest`

`useView` and Suspense

Pagination with `useListView`