HTTP mounting

Use case: versioned API under /api/v1

Sub-routers group related routes. Mount attaches them under a URL prefix without repeating the prefix on every route.

Example source: vow-examples/vow-web-server/mounted_api.vow

import lib.app
import lib.request
import lib.response
import lib.router
import lib.serve

fn user_by_id(req: request.Request) -> response.Response {
    let id = request.param(req, "id");
    let body = "{\"id\":\"" + id + "\"}";
    return response.json(body);
}

fn api_health(_req: request.Request) -> response.Response {
    return response.json("{\"api\":\"v1\"}");
}

fn main(caps: Caps) -> int {
    let sub = router.router_get(
        router.router_get(router.router_new(), "/health", api_health),
        "/users/:id",
        user_by_id
    );
    let a = app.mount(app.app(), "/api/v1", sub);
    return match caps.net {
        Some(cap) => serve.listen(a, cap, 8787),
        None => 0 - 1,
    };
}

Run

./vow run vow-examples/vow-web-server/mounted_api.vow -- --grant net:

curl -sf http://127.0.0.1:8787/api/v1/health
curl -sf http://127.0.0.1:8787/api/v1/users/42

Key concepts

URL	Handler	Notes
`GET /api/v1/health`	`api_health`	Sub-router route
`GET /api/v1/users/:id`	`user_by_id`	`:id` → `param(req, "id")`
`GET /api/v2/health`	—	404 (no mount)

Mount strips the prefix before dispatching to the child router — child routes register as /health, /users/:id, not /api/v1/health.

Unit test

assert app.try_handle(a, "GET /api/v1/users/99") == 200;
assert app.try_handle(a, "GET /api/v1/nope") == 404;

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