Fix fallback when no Kubernetes versions are available

If Rancher Desktop was previously started with a version, but the user
wipes the `k3s-versions.json` cache and we fail to download a new copy,
handle the error and disable Kubernetes instead of throwing an error.  To
make sure the user is aware of the issue, also pop a diagnostic to describe
the situation.

Signed-off-by: Mark Yen <mark.yen@suse.com>

pkg/rancher-desktop/backend/k3sHelper.ts

@@ -516,7 +516,12 @@ export default class K3sHelper extends events.EventEmitter {
 
           return;
         }
-        await this.updateCache();
+        try {
+          await this.updateCache();
+        } catch (ex) {
+          console.log(`Ignoring failure to get initial versions list: ${ ex }`);
+          // At this point this.versions is still empty.
+        }
       })();
     }
     this.versionFromChannel = {};
@@ -561,6 +566,8 @@ export default class K3sHelper extends events.EventEmitter {
 
   /**
    * The versions that are available to install.
+   * @note The list will be empty if the machine is offline and we have no
+   * cached versions.
    */
   get availableVersions(): Promise<SemanticVersionEntry[]> {
     return (async() => {

pkg/rancher-desktop/backend/kube/lima.ts

@@ -112,7 +112,7 @@ export default class LimaKubernetesBackend extends events.EventEmitter implement
             const result = await showMessageBox(options, true);
 
             if (result.response !== 0) {
-              return [undefined, false];
+              return [undefined, true];
             }
           }
           console.log(`Going with alternative version ${ newVersion.raw }`);
@@ -324,20 +324,24 @@ export default class LimaKubernetesBackend extends events.EventEmitter implement
   protected get desiredVersion(): Promise<semver.SemVer | undefined> {
     return (async() => {
       let availableVersions: SemanticVersionEntry[];
+      let available = true;
 
       try {
         availableVersions = await this.k3sHelper.availableVersions;
+
+        return await BackendHelper.getDesiredVersion(
+          this.cfg as BackendSettings,
+          availableVersions,
+          this.vm.noModalDialogs,
+          this.vm.writeSetting.bind(this.vm));
       } catch (ex) {
         console.error(`Could not get desired version: ${ ex }`);
+        available = false;
 
         return undefined;
+      } finally {
+        mainEvents.emit('diagnostics-event', { id: 'kube-versions-available', available });
       }
-
-      return await BackendHelper.getDesiredVersion(
-        this.cfg as BackendSettings,
-        availableVersions,
-        this.vm.noModalDialogs,
-        this.vm.writeSetting.bind(this.vm));
     })();
   }
 

pkg/rancher-desktop/backend/kube/wsl.ts

@@ -77,20 +77,24 @@ export default class WSLKubernetesBackend extends events.EventEmitter implements
   protected get desiredVersion(): Promise<semver.SemVer | undefined> {
     return (async() => {
       let availableVersions: SemanticVersionEntry[];
+      let available = true;
 
       try {
         availableVersions = await this.k3sHelper.availableVersions;
+
+        return await BackendHelper.getDesiredVersion(
+          this.cfg as BackendSettings,
+          availableVersions,
+          this.vm.noModalDialogs,
+          this.vm.writeSetting.bind(this.vm));
       } catch (ex) {
         console.error(`Could not get desired version: ${ ex }`);
+        available = false;
 
         return undefined;
+      } finally {
+        mainEvents.emit('diagnostics-event', { id: 'kube-versions-available', available });
       }
-
-      return await BackendHelper.getDesiredVersion(
-        this.cfg as BackendSettings,
-        availableVersions,
-        this.vm.noModalDialogs,
-        this.vm.writeSetting.bind(this.vm));
     })();
   }
 

pkg/rancher-desktop/backend/lima.ts

@@ -1813,14 +1813,23 @@ export default class LimaBackend extends events.EventEmitter implements VMBacken
         // Start the VM; if it's already running, this does nothing.
         await this.startVM();
 
+        // Clear the diagnostic about not having Kubernetes versions
+        mainEvents.emit('diagnostics-event', { id: 'kube-versions-available', available: true });
+
         if (config.kubernetes.enabled) {
           [kubernetesVersion, isDowngrade] = await this.kubeBackend.download(config);
 
-          if (typeof (kubernetesVersion) === 'undefined') {
-            // The desired version was unavailable, and the user declined a downgrade.
-            await this.setState(State.ERROR);
+          if (kubernetesVersion === undefined) {
+            if (isDowngrade) {
+              // The desired version was unavailable, and the user declined a downgrade.
+              await this.setState(State.ERROR);
 
-            return;
+              return;
+            }
+            // The desired version was unavailable, and we couldn't find a fallback.
+            // Notify the user, and turn off Kubernetes.
+            mainEvents.emit('diagnostics-event', { id: 'kube-versions-available', available: false });
+            this.writeSetting({ kubernetes: { enabled: false } });
           }
         }
 

pkg/rancher-desktop/backend/wsl.ts

@@ -1189,6 +1189,7 @@ export default class WSLBackend extends events.EventEmitter implements VMBackend
     const config = this.cfg = _.defaultsDeep(clone(config_),
       { containerEngine: { name: ContainerEngine.NONE } });
     let kubernetesVersion: semver.SemVer | undefined;
+    let isDowngrade = false;
 
     await this.setState(State.STARTING);
     this.currentAction = Action.STARTING;
@@ -1203,16 +1204,25 @@ export default class WSLBackend extends events.EventEmitter implements VMBackend
 
         if (config.kubernetes.enabled) {
           prepActions.push((async() => {
-            [kubernetesVersion] = await this.kubeBackend.download(config);
+            [kubernetesVersion, isDowngrade] = await this.kubeBackend.download(config);
           })());
         }
 
+        // Clear the diagnostic about not having Kubernetes versions
+        mainEvents.emit('diagnostics-event', { id: 'kube-versions-available', available: true });
+
         await this.progressTracker.action('Preparing to start', 0, Promise.all(prepActions));
-        if (config.kubernetes.enabled && typeof (kubernetesVersion) === 'undefined') {
-          // The desired version was unavailable, and the user declined a downgrade.
-          this.setState(State.ERROR);
+        if (config.kubernetes.enabled && kubernetesVersion === undefined) {
+          if (isDowngrade) {
+            // The desired version was unavailable, and the user declined a downgrade.
+            this.setState(State.ERROR);
 
-          return;
+            return;
+          }
+          // The desired version was unavailable, and we couldn't find a fallback.
+          // Notify the user, and turn off Kubernetes.
+          mainEvents.emit('diagnostics-event', { id: 'kube-versions-available', available: false });
+          this.writeSetting({ kubernetes: { enabled: false } });
         }
         if (this.currentAction !== Action.STARTING) {
           // User aborted before we finished

pkg/rancher-desktop/main/diagnostics/diagnostics.ts

@@ -50,6 +50,7 @@ export class DiagnosticsManager {
         import('./dockerCliSymlinks'),
         import('./kubeConfigSymlink'),
         import('./kubeContext'),
+        import('./kubeVersionsAvailable'),
         import('./limaDarwin'),
         import('./mockForScreenshots'),
         import('./pathManagement'),

pkg/rancher-desktop/main/diagnostics/kubeVersionsAvailable.ts

@@ -0,0 +1,44 @@
+import mainEvents from '../mainEvents';
+import { DiagnosticsCategory, DiagnosticsChecker, DiagnosticsCheckerResult } from './types';
+
+let kubeVersionsAvailable = true;
+
+mainEvents.on('diagnostics-event', (payload) => {
+  if (payload.id !== 'kube-versions-available') {
+    return;
+  }
+  kubeVersionsAvailable = payload.available;
+  mainEvents.invoke('diagnostics-trigger', instance.id);
+});
+
+/**
+ * KubeVersionsAvailable is a diagnostic that will be emitted when all of the
+ * following are met:
+ * - Kubernetes was configured to be enabled
+ * - The selected Kubernetes version is unavailable (e.g. user is offline)
+ * Once the diagnostic is triggered, it stays on until the backend is restarted.
+ */
+class KubeVersionsAvailable implements DiagnosticsChecker {
+  readonly id = 'KUBE_VERSIONS_AVAILABLE';
+  readonly category = DiagnosticsCategory.Kubernetes;
+  applicable(): Promise<boolean> {
+    return Promise.resolve(true);
+  }
+
+  check(): Promise<DiagnosticsCheckerResult> {
+    const description = [
+      'There are no issues with Kubernetes versions',
+      'Kubernetes has been disabled due to issues with fetching Kubernetes versions',
+    ][kubeVersionsAvailable ? 0 : 1];
+
+    return Promise.resolve({
+      passed: kubeVersionsAvailable,
+      description,
+      fixes:  [{ description: 'Check your network connection to update.k3s.io' }],
+    });
+  }
+}
+
+const instance = new KubeVersionsAvailable();
+
+export default instance;

pkg/rancher-desktop/main/mainEvents.ts

@@ -149,6 +149,7 @@ interface MainEventNames {
  * 'diagnostics-event' event.
  */
 type DiagnosticsEventPayload =
+  { id: 'kube-versions-available', available: boolean } |
   { id: 'path-management', fileName: string; error: Error | undefined };
 
 /**