Ignore preload as a dependency

There doesn't seem to be a sane setup that would set a preloaded
disposable as a property of another qube or a system property. The core
already ignores preloaded disposables in certain cases, do the same on
the client to not have derived applications such as Qube Manager having
to deal with it.

Fixes: QubesOS/qubes-issues#10227
For: QubesOS/qubes-issues#1512

Author: ben-grande

qubesadmin/tests/utils.py

@@ -35,7 +35,10 @@ def setUp(self):
             b'template2 class=TemplateVM state=Running\n' \
             b'vm2 class=AppVM state=Running\n' \
             b'sys-net class=AppVM state=Running\n' \
-            b'sys-firewall class=AppVM state=Running\n'
+            b'sys-firewall class=AppVM state=Running\n' \
+            b'test-dvm class=AppVM state=Running\n' \
+            b'disp1 class=DispVM state=Running\n' \
+            b'disp2 class=DispVM state=Running\n'
 
         self.global_properties = ['default_dispvm', 'default_netvm',
                                   'default_guivm', 'default_audiovm',
@@ -47,13 +50,20 @@ def setUp(self):
                 ('dom0', 'admin.property.Get', prop, None)] = \
                 b'0\x00default=True type=vm vm2'
 
-        self.vms = ['vm1', 'vm2', 'sys-net', 'sys-firewall',
-                    'template1', 'template2']
+        self.vms = [
+            'vm1', 'vm2', 'sys-net', 'sys-firewall', 'template1', 'template2',
+            'test-dvm', 'disp1', 'disp2',
+        ]
 
-        self.vm_properties = ['template', 'netvm', 'guivm', 'audiovm',
-                              'default_dispvm', 'management_dispvm']
+        self.vm_properties = [
+            'template', 'netvm', 'guivm', 'audiovm', 'default_dispvm',
+            'management_dispvm'
+        ]
 
         for vm in self.vms:
+            self.app.expected_calls[
+                (vm, 'admin.vm.property.Get', 'is_preload', None)
+            ] = b'2\0QubesNoSuchPropertyError\0\0invalid property\0'
             for prop in self.vm_properties:
                 if not prop.startswith('template') or \
                         not vm.startswith('template'):
@@ -65,6 +75,7 @@ def setUp(self):
                         (vm, 'admin.vm.property.Get', prop, None)] = \
                         b'2\0QubesNoSuchPropertyError\0\0invalid property\0'
 
+
     def test_00_only_global(self):
         result = qubesadmin.utils.vm_dependencies(self.app,
                                                   self.app.domains['vm2'])
@@ -114,6 +125,27 @@ def test_04_defaults(self):
 
         self.assertListEqual(result, [(self.app.domains['vm1'], 'netvm')])
 
+    def test_05_preloaded_disposables(self):
+        self.app.expected_calls[
+            ('disp1', 'admin.vm.property.Get', 'template', None)
+        ] = b'0\x00default=False type=vm test-dvm'
+        self.app.expected_calls[
+            ('disp2', 'admin.vm.property.Get', 'template', None)
+        ] = b'0\x00default=False type=vm test-dvm'
+        self.app.expected_calls[
+            ('disp1', 'admin.vm.property.Get', 'is_preload', None)
+        ] = b'0\x00default=False type=bool False'
+        self.app.expected_calls[
+            ('disp2', 'admin.vm.property.Get', 'is_preload', None)
+        ] = b'0\x00default=False type=bool True'
+
+        result = qubesadmin.utils.vm_dependencies(
+            self.app, self.app.domains['test-dvm']
+        )
+        self.assertListEqual(
+            result, [(self.app.domains['disp1'], 'template')]
+        )
+
 
 class TestVMExecEncode(qubesadmin.tests.QubesTestCase):
     def test_00_encode(self):

qubesadmin/utils.py

@@ -143,14 +143,26 @@ def vm_dependencies(app, reference_vm):
     for vm in app.domains:
         if vm == reference_vm:
             continue
+        is_preload = getattr(vm, "is_preload", False)
         for prop in vm_properties:
             if not hasattr(vm, prop):
                 continue
             try:
                 is_prop_default = vm.property_is_default(prop)
             except qubesadmin.exc.QubesPropertyAccessError:
                 is_prop_default = False
-            if reference_vm == getattr(vm, prop, None) and not is_prop_default:
+            if (
+                reference_vm == getattr(vm, prop, None)
+                and not is_prop_default
+                and not (
+                    is_preload
+                    and prop == "template"
+                    or (
+                        prop == "default_dispvm"
+                        and getattr(vm, "template", None) == vm
+                    )
+                )
+            ):
                 result.append((vm, prop))
 
     return result