Weather (executable)
Weather is a WebAssembly demonstration application that queries the Open-Meteo service. It asks for a city, resolves its coordinates, then displays Current, Hourly, Daily, and Meta views.
The app uses the Xila HTTPS client device at /devices/https_client, rather than directly calling browser JavaScript APIs. Its two public data sources are the Open-Meteo geocoding endpoint (geocoding-api.open-meteo.com) and forecast endpoint (api.open-meteo.com). When more than one geocoding result matches, the current implementation selects the first result.
Weather requires the HTTPS device and working network access. A browser or host with restricted networking cannot fetch forecasts; the headless container runner explicitly disables networking and is not an alternative for this app.
Request pipeline and data semantics
api::build_geocoding_url(city) generates an Open-Meteo geocoding request with count=10, language=en and format=json. It currently replaces spaces with plus signs rather than performing full URL percent-encoding for arbitrary user input. The app picks the first returned location rather than presenting an interactive disambiguation choice.
The forecast request includes current, hourly and daily measurements, requests 10 forecast days, and uses timezone=auto according to the location returned by the API. This is not Xila's system timezone configuration: the time-zone policy comes from Open-Meteo's response.
// API helpers in the application's own crate:
let geocode = weather::api::build_geocoding_url("Paris");
let forecast = weather::api::build_forecast_url(48.8566, 2.3522);
assert!(geocode.contains("count=10"));
assert!(forecast.contains("forecast_days=10"));These helpers only construct request URLs; they do not prove that the network or external service is available.
HTTPS transport and errors
On wasm32, net::https_get opens /devices/https_client, sends an HTTP/1.1 GET and parses response headers, HTTP status and payload. Chunked transfer encoding and Content-Length are handled by the guest's transport helper. Temporarily busy reads are retried with cooperative yields and occasional millisecond sleeps, with a finite limit; nontransient errors return to the UI.
The fetch sequence is geocoding → select first location → forecast. The forecast request is retried once when the first attempt fails. The app distinguishes network failures, invalid API JSON, missing locations and HTTP status failures, then updates Current/Hourly/Daily/Meta labels in its existing window.
The network operation is currently synchronous from the guest UI's refresh handler, so a slow fetch can temporarily delay UI responsiveness despite the small in_flight guard. The executable has no offline cache or local weather fallback; it neither reads nor writes application forecast files.
Source references
executables/weather/src/api.rs— geocoding/forecast query contracts.executables/weather/src/net.rs— HTTPS VFS device and HTTP framing.executables/weather/src/state.rs— fetch ordering, retries and error mapping.executables/weather/src/interface.rs— refresh event and views.- Networking — underlying host device.