Fix exception when no network selected

1. It's possible to erase the network when creating a host.
The exception raised was due to the ip_in_range validator
where a select using the network_id is performed.
This is now catched to raise a ValidationError.
2. Add some javascript to remove the is-invalid class on the network and
IP fields when changing them

JIRA INFRA-810 #action In Progress

app/network/forms.py

@@ -56,6 +56,10 @@ def starts_with_hostname(form, field):
 def ip_in_network(form, field):
     """Check that the IP is in the network"""
     network_id_field = form["network_id"]
+    if not network_id_field.data:
+        raise validators.ValidationError(
+            "Can't validate the IP. No network was selected."
+        )
     network = models.Network.query.get(network_id_field.data)
     ip = ipaddress.ip_address(field.data)
     if ip not in network.network_ip:

app/static/js/hosts.js

@@ -36,6 +36,7 @@ $(document).ready(function() {
     // and update the IP field
     var network_id = $("#network_id").val();
     if ( network_id !== "" ) {
+      $("#ip").removeClass("is-invalid");
       $.getJSON(
         $SCRIPT_ROOT + "/network/_retrieve_first_available_ip/" + network_id,
         function(json) {
@@ -83,6 +84,13 @@ $(document).ready(function() {
     set_default_ip();
   }
 
+  // On page load if the network_id is invalid, it's because an empty entry was submitted
+  // remove the default value to make it clear
+  if( ($("#hostForm").length || $("#interfaceForm").length) && $("#network_id").hasClass("is-invalid") ) {
+    var network_id_selectize = $("#network_id")[0].selectize;
+    network_id_selectize.clear(true);
+  }
+
   // Clear the default value so that the user can start typing directly
   // or click a dropdown item
   $("#network_id").next(".selectize-control").on( 'click', function () {
@@ -92,6 +100,8 @@ $(document).ready(function() {
 
   // Set the default IP when changing network
   $("#network_id").on('change', function() {
+    $(this).removeClass("is-invalid");
+    $(this).next(".selectize-control").removeClass("is-invalid");
     set_default_ip();
   });