fix(images): clear the image cache on sign-out

app/Devnull/Account.php

@@ -153,12 +153,13 @@ public function rememberUnreadRemotes(int $count): void
     }
 
     /**
-     * Signs this phone out: who it was, the badges, its pastéis and Remotes, every answer kept for a quick start,
-     * and your unsent drafts.
+     * Signs this phone out: who it was, the badges, its pastéis and Remotes, every answer and image kept for a
+     * quick start, and your unsent drafts.
      */
     public function forget(): void
     {
         app(ResponseCache::class)->flush();
+        ImageCache::clear();
         app(Stash::class)->forget($this->user()?->id);
         app(Outbox::class)->forgetAll($this->user()?->id);
 

app/Devnull/DownloadImages.php

@@ -66,6 +66,11 @@ public static function save(array $urls, ?float $until = null): int
                 $batch,
             ));
 
+            // Signing out empties the cache (see Account::forget), and this thread can't tell it happened otherwise.
+            if (app(Account::class)->user() === null) {
+                break;
+            }
+
             foreach ($batch as $index => $url) {
                 $response = $responses[$index] ?? null;
 

app/Devnull/ImageCache.php

@@ -3,6 +3,7 @@
 namespace App\Devnull;
 
 use Carbon\CarbonImmutable;
+use Illuminate\Support\Facades\File;
 
 /**
  * Remote images kept on the device: avatars, commit images and link preview
@@ -117,6 +118,18 @@ public static function takePrune(): ?int
         return $cache->startedAt - self::hours() * 3600;
     }
 
+    /**
+     * Deletes every image on the device, on sign-out, so the next person to
+     * sign in never sees what the last one was shown. What's drawn from now on
+     * comes from its URL.
+     */
+    public static function clear(): void
+    {
+        File::deleteDirectory(self::directory());
+
+        app(self::class)->sources = [];
+    }
+
     /**
      * Every image URL in an answer, wherever it's nested: people's avatars,
      * commits' images and link previews' images.

tests/Feature/ImageCacheTest.php

@@ -1,5 +1,6 @@
 <?php
 
+use App\Devnull\Account;
 use App\Devnull\Client;
 use App\Devnull\DownloadImages;
 use App\Devnull\FetchInBackground;
@@ -143,6 +144,7 @@ function imagesQueued(): array
 });
 
 it('keeps only what downloads as an image, and clears out images older than a day when asked to', function () {
+    signIn();
     $stale = cachedImage('https://avatars.githubusercontent.com/u/8?v=4', hoursAgo: 30);
     File::put(ImageCache::path('https://avatars.githubusercontent.com/u/9?v=4').'.part', 'half');
 
@@ -253,6 +255,7 @@ function imagesQueued(): array
 });
 
 it('brings an answer\'s images down with it when asked, before it comes back', function () {
+    signIn();
     Http::fake([
         'avatars.githubusercontent.com/*' => Http::response('png bytes', 200, ['Content-Type' => 'image/png']),
         'devnull.test/api/v1/log/following*' => Http::response(pageJson([commitJson(['author' => userJson(['avatar_url' => 'https://avatars.githubusercontent.com/u/2?v=4'])])])),
@@ -275,7 +278,28 @@ function imagesQueued(): array
     expect(File::exists(ImageCache::path('https://avatars.githubusercontent.com/u/3?v=4')))->toBeFalse();
 });
 
+it('empties the image folder on sign-out, and draws what it held from the URL again', function () {
+    signIn();
+    $url = 'https://avatars.githubusercontent.com/u/2?v=4';
+    $path = cachedImage($url);
+
+    expect(ImageCache::src($url))->toBe($path);
+
+    app(Account::class)->forget();
+
+    expect(File::isDirectory(ImageCache::directory()))->toBeFalse()
+        ->and(ImageCache::src($url))->toBe($url);
+});
+
+it('keeps no image that lands once nobody is signed in', function () {
+    Http::fake(['avatars.githubusercontent.com/*' => Http::response('png bytes', 200, ['Content-Type' => 'image/png'])]);
+
+    expect(DownloadImages::save(['https://avatars.githubusercontent.com/u/2?v=4']))->toBe(0)
+        ->and(File::exists(ImageCache::path('https://avatars.githubusercontent.com/u/2?v=4')))->toBeFalse();
+});
+
 it('gives images it waits on only the time that is left, and starts none once it is up', function () {
+    signIn();
     Http::fake(['avatars.githubusercontent.com/*' => Http::response('png bytes', 200, ['Content-Type' => 'image/png'])]);
 
     expect(DownloadImages::save(['https://avatars.githubusercontent.com/u/2?v=4'], until: microtime(true) - 1))->toBe(0);