Error Formatting

The error formatting in your router will be inferred all the way to your client (& React components)

Usage example highlighted

Adding custom formatting

server.ts
ts
const router = trpc.router<Context>()
  .formatError(({ shape, error }) => {
    return {
      ...shape,
      data: {
        ...shape.data,
        zodError:
          error.code === 'BAD_REQUEST' &&
          error.cause instanceof ZodError
            ? error.cause.flatten()
            : null,
      },
    };
  })

server.ts
ts
const router = trpc.router<Context>()
  .formatError(({ shape, error }) => {
    return {
      ...shape,
      data: {
        ...shape.data,
        zodError:
          error.code === 'BAD_REQUEST' &&
          error.cause instanceof ZodError
            ? error.cause.flatten()
            : null,
      },
    };
  })

Usage in React

components/MyComponent.tsx
tsx
export function MyComponent() {
  const mutation = trpc.useMutation('addPost');
  useEffect(() => {
    mutation.mutate({ title: 'example' });
  }, []);
  if (mutation.error?.data?.zodError) {
    // zodError will be inferred
    return (
      <pre>Error: {JSON.stringify(mutation.error.data.zodError, null, 2)}</pre>
    );
  }
  return <>[...]</>;
}

components/MyComponent.tsx
tsx
export function MyComponent() {
  const mutation = trpc.useMutation('addPost');
  useEffect(() => {
    mutation.mutate({ title: 'example' });
  }, []);
  if (mutation.error?.data?.zodError) {
    // zodError will be inferred
    return (
      <pre>Error: {JSON.stringify(mutation.error.data.zodError, null, 2)}</pre>
    );
  }
  return <>[...]</>;
}

All properties sent to formatError()

Since v8.x tRPC is compliant with JSON-RPC 2.0

ts
{
  error: TRPCError;
  type: ProcedureType | 'unknown';
  path: string | undefined;
  input: unknown;
  ctx: undefined | TContext;
  shape: DefaultErrorShape; // the default error shape
}

ts
{
  error: TRPCError;
  type: ProcedureType | 'unknown';
  path: string | undefined;
  input: unknown;
  ctx: undefined | TContext;
  shape: DefaultErrorShape; // the default error shape
}

DefaultErrorShape:

ts
interface DefaultErrorData {
  code: TRPC_ERROR_CODE_KEY;
  httpStatus: number;
  path?: string;
  stack?: string;
}
interface DefaultErrorShape
  extends TRPCErrorShape<TRPC_ERROR_CODE_NUMBER, DefaultErrorData> {
  message: string;
  code: TRPC_ERROR_CODE_NUMBER;
}

ts
interface DefaultErrorData {
  code: TRPC_ERROR_CODE_KEY;
  httpStatus: number;
  path?: string;
  stack?: string;
}
interface DefaultErrorShape
  extends TRPCErrorShape<TRPC_ERROR_CODE_NUMBER, DefaultErrorData> {
  message: string;
  code: TRPC_ERROR_CODE_NUMBER;
}