fix(instances): an ISO already in a CD-ROM of the VM is not added again

A CD-ROM form sent twice (a double click, a resent request) added a
second drive with the same ISO. The form is refused when the ISO is in a
CD-ROM of the VM's running or persistent definition; an empty drive may
still be added more than once. tr and zh too.

instances/tests/test_duplicate_devices.py

@@ -60,3 +60,16 @@ class DuplicateDeviceTests(TestCase):
         self.assertEqual(self.post("add_network", form),
                          [f"The VM already has a network device with MAC {MAC.upper()}"])
         self.proxy.add_network.assert_called_once()
+
+    def test_an_iso_in_a_cdrom_of_the_vm_is_not_added_again(self):
+        iso = "/var/lib/libvirt/isos/alma.iso"
+        self.proxy.get_iso_path.return_value = iso
+        with patch("instances.views.cdrom_bus_choices", return_value=["sata"]):
+            form = {"bus": "sata", "media": "alma.iso"}
+            self.post("add_cdrom", form)
+            self.proxy.attach_disk.assert_called_once()
+            self.proxy.get_media_devices.side_effect = lambda config=False: [{"path": iso, "dev": "sdb"}] if config else []
+            self.assertEqual(self.post("add_cdrom", form), ["alma.iso is already in a CD-ROM of this VM"])
+            # an empty drive may be added more than once
+            self.post("add_cdrom", {"bus": "sata", "media": ""})
+        self.assertEqual(self.proxy.attach_disk.call_count, 2)

instances/views.py

@@ -1626,6 +1626,11 @@ def add_cdrom(request, pk):
     if bus == "usb" and not image:
         messages.error(request, _("A USB CD-ROM needs an ISO image: libvirt has no empty USB drive"))
         return _back(request, pk, "disks")
+    path = instance.proxy.get_iso_path(image) if image else ""
+    # a form sent twice (a double click) adds the drive once
+    if path and path in {media["path"] for media in instance.media + instance.config_media}:
+        messages.error(request, _("%(image)s is already in a CD-ROM of this VM") % {"image": image})
+        return _back(request, pk, "disks")
 
     target = utils.get_new_disk_dev(
         instance.media + instance.config_media, instance.disks + instance.config_disks, bus
@@ -1634,7 +1639,7 @@ def add_cdrom(request, pk):
         with audit_vm(request, instance, f"add CD-ROM {target}" + (f" with {image}" if image else "")):
             instance.proxy.attach_disk(
                 target,
-                instance.proxy.get_iso_path(image) if image else "",
+                path,
                 disk_device="cdrom",
                 cache_mode="none",
                 target_bus=bus,