tRPC local / test link for testing

trpc-test-link.ts

/**
 * Terminating link that directly calls the tRPC router
 */
export function createTestLink<TRouter extends AnyRouter>(opts: {
    headers: () => Promise<Record<string, string>>;
    router: TRouter;
}): TRPCLink<TRouter> {
    return () => {
        return (runtime) => {
            return observable((observer) => {
                const invokeRouter = async () => {
                    const headers = await opts.headers();

                    const caller = opts.router.createCaller({
                        request: new Request(
                            "http://test.invalid" + runtime.op.path,
                            { headers },
                        ),
                    }) as any;

                    const res = await caller[runtime.op.path](
                        runtime.op.input,
                    ).catch((error: any) => {
                        console.log(
                            `tRPC Error in ${runtime.op.type}:${runtime.op.path}\n`,
                            error.stack,
                        );
                        throw new TRPCClientError(
                            error.message || "Unknown error",
                            {
                                cause: error,
                            },
                        );
                    });

                    observer.next({
                        result: {
                            data: res,
                        },
                    });
                    observer.complete();
                };

                invokeRouter().catch((error) => {
                    observer.error(error);
                });
            });
        };
    };
}

usage.ts

const client = createTRPCProxyClient<CLIRouterType>({
    links: [
        createTestLink({
            headers: myCreateHeadersFn,
            router: TheTrpcRouter,
        }),
    ],
});