allow launching existing or installing new if either fails

qt/launcher-gui/src/routes/Action.svelte

@@ -7,32 +7,39 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     import type { ExistingVersions, Versions } from "@generated/anki/launcher_pb";
     import Row from "$lib/components/Row.svelte";
     import EnumSelector from "$lib/components/EnumSelector.svelte";
+    import Warning from "./Warning.svelte";
+    import Spinner from "./Spinner.svelte";
 
     let {
-        releases,
-        existing,
+        releasesPromise,
+        existingPromise,
         allowBetas,
         choose,
         uninstall,
     }: {
-        releases: Versions;
-        existing: ExistingVersions;
+        releasesPromise: Promise<Versions>;
+        existingPromise: Promise<ExistingVersions>;
         allowBetas: boolean;
         choose: (version: string, existing: boolean, current?: string) => void;
         uninstall: (() => void) | null;
     } = $props();
 
+    // TODO: replace once svelte's experimental async mode is on
+    let releases = $state(undefined as Versions | undefined);
+    let existing = $state(undefined as ExistingVersions | undefined);
+    releasesPromise.then((r) => (releases = r));
+    existingPromise.then((r) => (existing = r));
+
     let availableVersions = $derived(
-        releases.all
+        releases?.all
             .filter((v) => allowBetas || !v.isPrerelease)
             .map((v) => ({ label: v.version, value: v.version })),
     );
 
-    let latest = $derived(availableVersions[0]?.value ?? null);
-    let selected = $derived(availableVersions[0]?.value ?? null);
-    let current = $derived(existing.current?.version);
-
-    let pyprojectModified = $derived(existing.pyprojectModifiedByUser);
+    let latest = $derived(availableVersions?.[0]?.value);
+    let selected = $derived(availableVersions?.[0]?.value);
+    let current = $derived(existing!?.current?.version);
+    let pyprojectModified = $derived(existing?.pyprojectModifiedByUser);
 
     function _choose(version: string, keepExisting: boolean = false) {
         choose(version, keepExisting, current);
@@ -40,6 +47,9 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 </script>
 
 <div class="group">
+    {#await releasesPromise}
+        <Spinner label={$tr.launcherLoadingVersions()} />
+    {:then}
         {#if latest != null && latest != current}
             <Row class="centre m-3">
                 <button class="btn btn-primary" onclick={() => _choose(latest)}>
@@ -53,6 +63,12 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
                 </button>
             </Row>
         {/if}
+    {:catch}
+        <Warning warning={$tr.launcherFailedToGetReleases()} className="alert-danger" />
+    {/await}
+    {#await existingPromise}
+        <Spinner label={$tr.launcherCheckingExisting()} />
+    {:then}
         {#if current != null}
             <Row class="centre m-3">
                 <button class="btn btn-primary" onclick={() => _choose(current, true)}>
@@ -64,6 +80,8 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
                 </button>
             </Row>
         {/if}
+    {/await}
+    {#if availableVersions}
         <Row class="centre m-3">
             <button
                 class="btn btn-primary"
@@ -79,6 +97,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
                 <EnumSelector bind:value={selected} choices={availableVersions} />
             </div>
         </Row>
+    {/if}
     {#if uninstall != null}
         <Row class="centre m-3">
             <button class="btn btn-primary" onclick={uninstall}>

qt/launcher-gui/src/routes/Normal.svelte

@@ -23,7 +23,6 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     import Term from "./Term.svelte";
     import AnkiWillStart from "./AnkiWillStart.svelte";
     import type { Terminal } from "@xterm/xterm";
-    import { tick } from "svelte";
 
     let {
         options,
@@ -39,9 +38,9 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
     footer = _footer;
 
-    let releasesPromise = $state(getAvailableVersions({}, { alertOnError: false }));
-    let existingPromise = $state(getExistingVersions({}, { alertOnError: false }));
-    let loadPromise = $derived(Promise.all([releasesPromise, existingPromise]));
+    let releasesPromise = $state(getAvailableVersions({}));
+    let existingPromise = $state(getExistingVersions({}));
+    let loadPromise = $derived(Promise.any([releasesPromise, existingPromise]));
 
     let allowBetas = $state(options.allowBetas);
     let downloadCaching = $state(options.downloadCaching);
@@ -77,17 +76,30 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
             <Row class="centre m-3">
                 <Spinner label={$tr.launcherLoadingVersions()} />
             </Row>
-        {:then [releases, existing]}
-            <Action {releases} {existing} {allowBetas} {choose} {uninstall} />
-        {:catch e}
-            <Warning
-                warning={$tr.lauuncherFailedToLoadVersions()}
-                className="alert-danger"
+        {:then}
+            <Action
+                {releasesPromise}
+                {existingPromise}
+                {allowBetas}
+                {choose}
+                {uninstall}
             />
+            {#await releasesPromise catch e}
                 <Row>
                     <pre>{e.message}</pre>
                 </Row>
             {/await}
+        {:catch e: AggregateError}
+            <Warning
+                warning={$tr.launcherFailedToGetExistingAndAvailable()}
+                className="alert-danger"
+            />
+            {#each e.errors as err}
+                <Row>
+                    <pre>{err.message}</pre>
+                </Row>
+            {/each}
+        {/await}
     {:else}
         <Row class="centre m-3">
             <AnkiWillStart {res} />