fix(instances): an empty panel says what to do next

- The VM list with no VMs no longer also says that no VM matches the
  search and the state.
- The New VM dialog with no compute yet says to add the first host, with a
  link to the Computes page (and links there when none is reachable).
- The new VM page on a host without a running storage pool or a network
  says what to add or start and where, instead of "You haven't defined any
  storage pools" (also when pools exist but are stopped) and "network
  pools".

instances/templates/allinstances.html

@@ -63,11 +63,13 @@
         {% else %}
             {% include 'allinstances_index_nongrouped.html' %}
         {% endif %}
+        {% if instances %}
         {# table_filter.js shows it while no row matches #}
         <div id="no-match" class="text-center text-body-secondary py-4" hidden>
             {% trans "No VM matches the search and the state." %}
             <button type="button" class="btn btn-link" id="clear-filters">{% trans "Clear the filters" %}</button>
         </div>
+        {% endif %}
     </div>
     <div class="modal fade" id="find-address" tabindex="-1" aria-labelledby="find-address-title" aria-hidden="true"
          data-url="{% url 'instances:find_address' %}" data-failed="{% trans "The search did not go through. Try again." %}"

instances/templates/create_inst_block.html

@@ -44,7 +44,12 @@
                         </div>
                     </a>
                     {% empty %}
-                    <p>{% trans "No compute is reachable." %}</p>
+                    {% url 'computes' as computes_url %}
+                    {% if computes %}
+                    <p>{% blocktrans %}No compute is reachable: see the <a href="{{ computes_url }}">Computes</a> page.{% endblocktrans %}</p>
+                    {% else %}
+                    <p>{% blocktrans %}There is no compute yet: add the first host on the <a href="{{ computes_url }}">Computes</a> page.{% endblocktrans %}</p>
+                    {% endif %}
                     {% endfor %}
                 </div>
             </div>

instances/tests/test_create_dialog_cpu.py

@@ -142,9 +142,19 @@ class CreateDialogHostsTestCase(TestCase):
     def test_only_reachable_computes_are_listed(self):
         dialog = self.dialog({"cd2"})
         self.assertEqual([e.text for e in dialog.xpath(".//a/div/div[1]")], ["cd2"])
-        self.assertNotIn("No compute is reachable.", dialog.text_content())
+        self.assertNotIn("No compute is reachable", dialog.text_content())
 
     def test_no_reachable_compute_is_said(self):
         dialog = self.dialog(set())
-        self.assertEqual(dialog.xpath(".//a"), [])
-        self.assertIn("No compute is reachable.", dialog.text_content())
+        self.assertEqual(dialog.xpath(".//a[contains(@class, 'list-group-item')]"), [])
+        self.assertIn("No compute is reachable: see the Computes page.", dialog.text_content())
+
+    def test_a_panel_without_computes_says_to_add_one(self):
+        # the first visit: the dialog and the list lead to the Computes page, and no filter is said to hide VMs
+        Compute.objects.all().delete()
+        response = self.client.get(reverse("instances:index"))
+        dialog = html.fromstring(response.content).get_element_by_id("AddInstance")
+        self.assertIn("There is no compute yet: add the first host on the Computes page.", dialog.text_content())
+        self.assertEqual(dialog.xpath(".//p/a/@href"), [reverse("computes")])
+        self.assertContains(response, "There are no VMs here yet.")
+        self.assertNotContains(response, "No VM matches the search")

instances/tests/test_create_form_input.py

@@ -61,7 +61,7 @@ class CreateFormInputTests(TestCase):
             _, response = render_create_page(self)
         self.assertIsNone(response.context["vm_form"])
         self.assertEqual(html.fromstring(response.content).xpath("//button[@name='create']"), [])
-        self.assertTrue(any("storage pools" in str(m) for m in response.context["messages"]))
+        self.assertTrue(any("no running storage pool" in str(m) for m in response.context["messages"]))
 
     def test_a_host_that_cannot_be_read_is_a_message(self):
         import libvirt

instances/tests/test_create_instance.py

@@ -162,6 +162,11 @@ class CreateInstanceViewTests(TestCase):
 
         self.assertEqual(response.status_code, 200)
         conn.get_firmwares.assert_called_once_with("x86_64", "q35")
+        # a fresh host: what to do, not that the user defined nothing
+        self.assertContains(response, "This host has no running storage pool for the VM's disks: add or start one on its Storage page.")
+        conn.get_storages.return_value = ["default"]
+        response = self.client.get(reverse("instances:create_instance", args=[compute.id, "x86_64", "q35"]))
+        self.assertContains(response, "This host has no network for the VM: add one on its Networks page.")
 
 
 class NicMacsTestCase(SimpleTestCase):

instances/views.py

@@ -2581,9 +2581,9 @@ def create_instance(request, compute_id, arch, machine):
         tpm_support = bool(conn.get_tpm_model(arch, machine))
 
         if not storages:
-            raise util.OperationError(_("You haven't defined any storage pools"))
+            raise util.OperationError(_("This host has no running storage pool for the VM's disks: add or start one on its Storage page."))
         if not networks:
-            raise util.OperationError(_("You haven't defined any network pools"))
+            raise util.OperationError(_("This host has no network for the VM: add one on its Networks page."))
 
         vm_form = NewVMForm(initial={
             # a default this host does not offer is no choice: the select asks for one