When providing a FieldDefaults under a ListInstance for a taxonomy fi…

…eld and setting the ID to -1, this code change will make sure to update the -1 to the actual ID as it exists in the hidden TaxonomyHiddenList list or if it doesn't exist in there yet, create a new entry for it and update the -1 to the ID of this new entry

Core/OfficeDevPnP.Core/Framework/Provisioning/ObjectHandlers/ObjectField.cs

@@ -407,7 +407,7 @@ private static void ValidateTaxonomyFieldDefaultValue(TaxonomyField field)
             }
         }
 
-        private static string GetTaxonomyFieldValidatedValue(TaxonomyField field, string defaultValue)
+        public static string GetTaxonomyFieldValidatedValue(TaxonomyField field, string defaultValue)
         {
             string res = null;
             object parsedValue = null;

Core/OfficeDevPnP.Core/Framework/Provisioning/ObjectHandlers/ObjectListInstance.cs

@@ -337,7 +337,22 @@ private static void ProcessFieldDefaults(Web web, TokenParser parser, ListInfo l
                 {
                     var fieldDefaultValue = parser.ParseString(fieldDefault.Value);
                     var field = listInfo.SiteList.Fields.GetByInternalNameOrTitle(fieldDefault.Key);
+
+                    // If there has been a default value specified, request the type of field so we know if we have to deal with the default value in a special way according to the field type. If no default has been specified, we can simply set the default to NULL, regardless of the field type.
+                    if (!string.IsNullOrEmpty(fieldDefaultValue))
+                    {
+                        // A default value has been provided, request the field type so we know if we have to apply special handling for the type of field
+                        web.Context.Load(field, f => f.TypeAsString);
+                        web.Context.ExecuteQueryRetry();
+
+                        // In the case of a Taxonomy field, ensure that the default value which is in the format <ID>;#<NAME>|<TERMGUID> has its ID match with the actual ID in the TaxonomyHiddenList of the target site if the ID has been set to -1.
+                        if (field.TypeAsString == "TaxonomyFieldType" || field.TypeAsString == "TaxonomyFieldTypeMulti")
+                        {
+                            fieldDefaultValue = ObjectField.GetTaxonomyFieldValidatedValue(web.Context.CastTo<TaxonomyField>(field), fieldDefaultValue);
+                        }
+                    }
                     field.DefaultValue = fieldDefaultValue;
+
                     field.Update();
                     web.Context.ExecuteQueryRetry();
                 }