Check that Web Bluetooth is available (#223)

Bluetooth can be blocked by system policies.

Author: microbit-robert

src/App.svelte

@@ -11,7 +11,6 @@
     compatibility,
     isCompatibilityWarningDialogOpen,
   } from './script/stores/uiStore';
-  import { checkCompatibility } from './script/compatibility/CompatibilityChecker';
   import IncompatiblePlatformView from './views/IncompatiblePlatformView.svelte';
   import CompatibilityWarningDialog from './components/CompatibilityWarningDialog.svelte';
   import Router from './router/Router.svelte';
@@ -23,7 +22,6 @@
   import HelpMenu from './components/control-bar/control-bar-items/HelpMenu.svelte';
   import SettingsMenu from './components/control-bar/control-bar-items/SettingsMenu.svelte';
   import { onMount } from 'svelte';
-  import { get } from 'svelte/store';
   import ConnectDialogContainer from './components/connection-prompt/ConnectDialogContainer.svelte';
   import { Paths, currentPath, getTitle, navigate } from './router/paths';
   import HomeIcon from 'virtual:icons/ri/home-2-line';
@@ -34,7 +32,7 @@
   } from './script/stores/connectDialogStore';
 
   onMount(() => {
-    const { bluetooth, usb } = get(compatibility);
+    const { bluetooth, usb } = $compatibility;
     // Value must switch from false to true after mount to trigger dialog transition
     isCompatibilityWarningDialogOpen.set(!bluetooth && !usb);
 
@@ -55,7 +53,7 @@
 
 <Router>
   <div class="sr-only" bind:this={routeAnnouncementEl} aria-live="polite" />
-  {#if !checkCompatibility().platformAllowed}
+  {#if !$compatibility.platformAllowed}
     <!-- Denies mobile users access to the platform -->
     <IncompatiblePlatformView />
   {:else}

src/script/compatibility/CompatibilityChecker.ts

@@ -15,7 +15,7 @@ export type CompatibilityStatus = {
   webGL: boolean;
 };
 
-export function checkCompatibility(): CompatibilityStatus {
+export async function checkCompatibility(): Promise<CompatibilityStatus> {
   if (localStorage.getItem('isTesting')) {
     return { bluetooth: true, usb: true, platformAllowed: true, webGL: true };
   }
@@ -37,9 +37,10 @@ export function checkCompatibility(): CompatibilityStatus {
     platformType = 'desktop';
   }
   const isPlatformAllowed = isDevMode || !nonAllowedPlatforms.includes(platformType);
+  const bluetooth = navigator.bluetooth && (await navigator.bluetooth.getAvailability());
 
   return {
-    bluetooth: !!navigator.bluetooth,
+    bluetooth,
     usb: !!navigator.usb,
     platformAllowed: isPlatformAllowed,
     webGL: webGL,

src/script/stores/uiStore.ts

@@ -20,7 +20,7 @@ import { DeviceRequestStates } from '../microbit-interfacing/MicrobitConnection'
 let text: (key: string, vars?: object) => string;
 t.subscribe(t => (text = t));
 
-export const compatibility = writable<CompatibilityStatus>(checkCompatibility());
+export const compatibility = writable<CompatibilityStatus>(await checkCompatibility());
 
 export const isCompatibilityWarningDialogOpen = writable<boolean>(false);