forms: clean context before displaying a new page (#48950)

tests/form_pages/test_all.py

@@ -6157,6 +6157,63 @@ def test_dynamic_item_field_from_custom_view_on_cards(pub):
     assert formdef.data_class().select()[0].data['1_structured']['item'] == 'baz'
 
 
+def test_item_field_from_cards_check_lazy_live(pub):
+    create_user(pub)
+    formdef = create_formdef()
+    formdef.data_class().wipe()
+
+    CardDef.wipe()
+    carddef = CardDef()
+    carddef.name = 'items'
+    carddef.digest_template = '{{form_var_name}}'
+    carddef.fields = [
+        fields.StringField(id='0', label='string', varname='name'),
+        fields.StringField(id='1', label='string', varname='attr'),
+    ]
+    carddef.store()
+    carddef.data_class().wipe()
+    for i, value in enumerate(['foo', 'bar', 'baz']):
+        carddata = carddef.data_class()()
+        carddata.data = {
+            '0': value,
+            '1': 'attr%s' % i,
+        }
+        carddata.just_created()
+        carddata.store()
+
+    ds = {'type': 'carddef:%s' % carddef.url_name}
+    formdef.fields = [
+        fields.PageField(id='0', label='1st page', type='page'),
+        fields.ItemField(id='1', label='string', type='item', varname='item', data_source=ds),
+        fields.PageField(id='2', label='2nd page', type='page'),
+        fields.CommentField(id='3', label='live value: {{ form_var_item_live_var_attr }}', type='comment'),
+        fields.PageField(id='4', label='3rd page', type='page'),
+    ]
+    formdef.store()
+
+    resp = get_app(pub).get('/test/')
+    resp.form['f1'] = '2'
+    resp = resp.form.submit('submit')  # -> 2nd page
+    assert 'live value: attr1' in resp
+
+    # add a field with a condition on first page and third page
+    formdef.fields[1:1] = [
+        fields.StringField(id='5', label='field with condition', type='string',
+            required=False, condition={'type': 'django', 'value': '1'}),
+    ]
+    formdef.fields.append(
+        fields.StringField(id='6', label='second field with condition', type='string',
+            required=False, condition={'type': 'django', 'value': '1'}))
+    formdef.store()
+    resp = get_app(pub).get('/test/')
+    resp.form['f1'] = '2'
+    resp = resp.form.submit('submit')  # -> 2nd page
+    assert 'live value: attr1' in resp
+    resp = resp.form.submit('submit')  # -> 3rd page
+    resp = resp.form.submit('previous')  # -> 2nd page
+    assert 'live value: attr1' in resp
+
+
 def test_item_field_with_disabled_items(http_requests, pub):
     user = create_user(pub)
     formdef = create_formdef()

wcs/forms/root.py

@@ -980,6 +980,7 @@ class FormPage(Directory, FormTemplateMixin):
 
             # the page has been successfully submitted, maybe new pages
             # should be revealed.
+            self.clean_submission_context()
             self.feed_current_data(magictoken)
             self.reset_pages_cache()