H
Hono•4w ago
edproton

Generic Types Not Working as Expected

I'm facing an issue with generic types in a PaginatedResponse setup. Here's my use case: Code Example: 
export interface PaginatedResponse<T> {
  items: T[];
  metadata: {
    total: number;
    page: number;
    limit: number;
    pages: number;
  };
}

export type BookingWithRelations = Prisma.BookingGetPayload<{
  select: {
    startTime: true;
    endTime: true;
    title: true;
    status: true;
    host: {
      select: {
        id: true;
        name: true;
        image: true;
      };
    };
    participants: {
      select: {
        id: true;
        name: true;
        image: true;
      };
    };
  };
}>;

// Returning this structure in a JSON response
return c.json<PaginatedResponse<BookingWithRelations>>(
  {
    items: [],
    metadata: {
      limit: 1,
      page: 1,
      total: 1,
      pages: 1,
    },
  },
  200
);
export interface PaginatedResponse<T> {
  items: T[];
  metadata: {
    total: number;
    page: number;
    limit: number;
    pages: number;
  };
}

export type BookingWithRelations = Prisma.BookingGetPayload<{
  select: {
    startTime: true;
    endTime: true;
    title: true;
    status: true;
    host: {
      select: {
        id: true;
        name: true;
        image: true;
      };
    };
    participants: {
      select: {
        id: true;
        name: true;
        image: true;
      };
    };
  };
}>;

// Returning this structure in a JSON response
return c.json<PaginatedResponse<BookingWithRelations>>(
  {
    items: [],
    metadata: {
      limit: 1,
      page: 1,
      total: 1,
      pages: 1,
    },
  },
  200
);
The Problem: The client-side response lacks type safety. Even though the generic type PaginatedResponse<BookingWithRelations> is correctly defined, the returned response doesn't enforce or reflect the expected type safety. I'm unsure if this is due to a limitation in the type inference, serialization, or something else entirely. --- Question: How can I ensure type safety is preserved in the client for such scenarios?
Any ideas or workarounds would be greatly appreciated! 🙏
---
2 Replies
ambergristle
ambergristle•4w ago
there are a few patterns that can break hono client type inference, namely: - abstracting controller logic without using createFactory - defining method handlers as independent statements (rather than chaining) for more info, check out the best practices docs: https://hono.dev/docs/guides/best-practices
Best Practices - Hono
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ambergristle
ambergristle•4w ago
it's hard to say more without knowing how you've set up your backend

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