Router Context with ctx.assert

[kouhaidev]

When using ctx.assert, you need to add a type annotation for the ctx variable:

const router = new Router<AppState>();

router.post("/channels/:id/threads", async (ctx) => {
  ctx.assert(ctx.state.auth, 403);  // Assertions require every name in the call target to be declared with an explicit type annotation.deno-ts(2775)

  const id = ctx.params.id;
  // etc
})

The naive way of getting this working is to annotate ctx: RouterContext. That looks like this:

const router = new Router<AppState>();

type RouterCtxWithState<R extends string, S extends State> = RouterContext<
  R,
  RouteParams<R>,
  S
>;

router.post(
  "/channels/:id/threads",
  async (ctx: RouterCtxWithState<"/channels/:id/threads", AppState>) => {
    ctx.assert(ctx.state.auth, 403);
    const id = ctx.params.id;
    // etc
})

This is pretty verbose, and also repeats itself. Is there a better way?