Fix registration form redirecting when max_users is falsy

app/Http/Controllers/Auth/RegisterController.php

@@ -157,10 +157,11 @@ class RegisterController extends Controller
                 $count = User::where(function ($q) {
                     return $q->whereNull('status')->orWhereNotIn('status', ['deleted', 'delete']);
                 })->count();
-                if ($limit <= $count) {
+                // A falsy max_users means "no limit" (matches register() and the
+                // help view). Guard on $limit so 0/null/'' does not redirect.
+                if ($limit && $limit <= $count) {
                     return redirect(route('help.instance-max-users-limit'));
                 }
-                abort_if($limit <= $count, 404);
 
                 return view('auth.register');
             } else {

tests/Feature/Auth/RegisterTest.php

@@ -103,3 +103,36 @@ it('redirects authenticated users away from the register page', function () {
         ->get('/register')
         ->assertRedirect();
 });
+
+it('shows the registration form when enforce_max_users is on but max_users is falsy', function () {
+    // Falsy max_users means "no limit"; the GET form must not redirect to the
+    // instance-full page (must match the POST handler and the help view).
+    config(['pixelfed.open_registration' => true]);
+    config(['pixelfed.enforce_max_users' => true]);
+    config(['pixelfed.max_users' => 0]);
+
+    $this->get('/register')
+        ->assertOk();
+});
+
+it('redirects the registration form when a real max_users limit is reached', function () {
+    config(['pixelfed.open_registration' => true]);
+    config(['pixelfed.enforce_max_users' => true]);
+    config(['pixelfed.max_users' => 1]);
+
+    User::factory()->create();
+
+    $this->get('/register')
+        ->assertRedirect(route('help.instance-max-users-limit'));
+});
+
+it('shows the registration form when under a real max_users limit', function () {
+    config(['pixelfed.open_registration' => true]);
+    config(['pixelfed.enforce_max_users' => true]);
+    config(['pixelfed.max_users' => 1000]);
+
+    User::factory()->create();
+
+    $this->get('/register')
+        ->assertOk();
+});