Use related model_id field to build domain

base_dav/models/dav_collection.py

@@ -7,9 +7,10 @@ import time
 from operator import itemgetter
 from urllib.parse import quote_plus
 
-import vobject
 from odoo import api, fields, models, tools
 
+import vobject
+
 # pylint: disable=missing-import-error
 from ..controllers.main import PREFIX
 from ..radicale.collection import Collection, FileItem, Item

base_dav/models/dav_collection_field_mapping.py

@@ -4,10 +4,11 @@
 
 import datetime
 
+from odoo import api, fields, models, tools
+
 import dateutil
 import vobject
 from dateutil import tz
-from odoo import api, fields, models, tools
 
 
 class DavCollectionFieldMapping(models.Model):
@@ -34,6 +35,10 @@ class DavCollectionFieldMapping(models.Model):
         required=True,
         help="Field of the model the values are mapped to",
     )
+    model_id = fields.Many2one(
+        'ir.model',
+        related='collection_id.model_id',
+    )
     import_code = fields.Text(
         help="Code to import the value from a vobject. Use the variable "
              "result for the output of the value and item as input"

base_dav/views/dav_collection.xml

@@ -51,9 +51,10 @@
             <form>
                 <group>
                     <field name="collection_id" invisible="1"/>
+                    <field name="model_id" invisible="1"/>
                     <field name="name"/>
                     <field name="mapping_type"/>
-                    <field name="field_id" domain="[('model_id', '=', collection_id.model_id)]"/>
+                    <field name="field_id" domain="[('model_id', '=', model_id)]"/>
                     <field name="import_code" attrs="{'invisible': [('mapping_type', '!=', 'code')]}"/>
                     <field name="export_code" attrs="{'invisible': [('mapping_type', '!=', 'code')]}"/>
                 </group>
@@ -73,5 +74,4 @@
         action="action_dav_collection"
         sequence="100"
     />
-
 </odoo>