fix(instances): the VM lists show the VMs by name

The Instances page (grouped and not) and a host's Instances page read
the VMs without an order, so they showed in whatever order the database
returned them: insertion order on SQLite, any order on PostgreSQL,
where it changed between page loads and made a state test fail at
random in CI. They are now ordered by name.

computes/views.py

@@ -104,9 +104,7 @@ def instances(request, compute_id):
     compute = get_object_or_404(Compute, pk=compute_id)
 
     utils.refresh_instance_database(compute)
-    instances = Instance.objects.filter(compute=compute).prefetch_related(
-        "userinstance_set"
-    )
+    instances = Instance.objects.filter(compute=compute).order_by("name").prefetch_related("userinstance_set")
 
     return render(
         request, "computes/instances.html",

instances/tests/test_states.py

@@ -133,6 +133,20 @@ class StateTests(TestCase):
         self.assertEqual([r.xpath("td[@data-sort]/@data-sort") for r in rows[1:2]], [["2", "2097152"]])
 
 
+    def test_the_lists_show_the_vms_by_name(self):
+        # the first VM made comes last by name: the database's own order is not the list's
+        Instance.objects.filter(pk=self.vms[0].pk).update(name="st-vm-9")
+        by_name = [LABELS[state] for state in [*list(LABELS)[1:], 0]]
+        for style in ("grouped", "nongrouped"):
+            AppSettings.objects.filter(key="VIEW_INSTANCES_LIST_STYLE").update(value=style)
+            page = html.fromstring(self.get(self.admin, reverse("instances:index")))
+            with self.subTest(style=style):
+                self.assertEqual(page.xpath("//tbody//tr//@data-state"), by_name)
+        page = html.fromstring(self.get(self.admin, reverse("instances", args=[self.compute.id])))
+        names = [name.strip() for name in page.xpath("//tbody//tr//a[starts-with(normalize-space(), 'st-vm-')]/text()")]
+        self.assertEqual(names, sorted(names))
+
+
 class DetailStateTests(TestCase):
     """The VM page names every state and offers a forced power off where only that helps."""
 

instances/views.py

@@ -27,7 +27,7 @@ from django.contrib.auth.models import User
 from django.core import signing
 from django.core.exceptions import PermissionDenied, ValidationError
 from django.http import Http404, HttpResponse, JsonResponse
-from django.db.models import prefetch_related_objects
+from django.db.models import Prefetch, prefetch_related_objects
 from django.shortcuts import get_object_or_404, redirect, render
 from django.urls import reverse
 from django.utils import timezone
@@ -72,16 +72,18 @@ def index(request):
     computes = list(Compute.objects.all().order_by("name"))
     for compute in computes:
         utils.refr(compute)
-    prefetch_related_objects(computes, "instance_set__userinstance_set")
+    # each host's VMs by name: the database keeps no order of its own
+    prefetch_related_objects(computes, Prefetch("instance_set", queryset=Instance.objects.order_by("name")),
+                             "instance_set__userinstance_set")
 
     show_hosts = request.user.is_superuser or request.user.has_perm("instances.view_instances")
     own_hosts_down = False
     if show_hosts:
-        instances = Instance.objects.all().prefetch_related("userinstance_set")
+        instances = Instance.objects.order_by("name").prefetch_related("userinstance_set")
     else:
         instances = Instance.objects.filter(
             userinstance__user=request.user
-        ).prefetch_related("userinstance_set")
+        ).order_by("name").prefetch_related("userinstance_set")
         # other users get no host names or connection errors, only whether
         # a host of their own VMs is down
         own = set(instances.values_list("compute_id", flat=True))