form: fix dynamic item field value on reload (#48495)

tests/form_pages/test_block.py

@@ -1,4 +1,8 @@
 # -*- coding: utf-8 -*-
+import json
+import mock
+
+from django.utils.six import StringIO
 
 import pytest
 from webtest import Upload
@@ -870,3 +874,81 @@ def test_block_post_condition_on_2nd_page(pub, blocks_feature):
     assert 'You shall not pass.' not in resp.text
     resp = resp.form.submit('submit')  # -> submit
     resp = resp.follow()
+
+
+@mock.patch('wcs.qommon.misc.urlopen')
+def test_block_with_dynamic_item_field(mock_urlopen, pub, blocks_feature):
+    def data_source(url):
+        url, query = url.split('?q=')
+        payload = []
+        if query == 'foo':
+            payload = [{'id': '1', 'text': 'foo'}]
+        elif query == 'bar':
+            payload = [{'id': '2', 'text': 'bar'}]
+        return StringIO(json.dumps({'data': payload}))
+    mock_urlopen.side_effect = lambda url: data_source(url)
+
+    FormDef.wipe()
+    BlockDef.wipe()
+
+    block = BlockDef()
+    block.name = 'foobar'
+    block.fields = [
+        fields.StringField(
+            id='123', required=True, label='Test',
+            type='string', varname='foo'),
+    ]
+    block.store()
+
+    formdef = FormDef()
+    formdef.name = 'foo'
+    formdef.fields = [
+        fields.StringField(
+            id='1', label='field 1',
+            type='string', varname='foo'),
+        fields.ItemField(
+            id='2', label='field 2',
+            varname='bar', data_source={'type': 'json', 'value': 'http://whatever/data-source?q={{form_var_foo|default:""}}'}),
+        fields.BlockField(id='3', label='block', type='block:foobar', max_items=3),
+    ]
+    formdef.store()
+
+    app = get_app(pub)
+
+    resp = app.get(formdef.get_url())
+    # select first field
+    resp.form['f1'] = 'foo'
+    live_resp = app.post('/foo/live?modified_field_id=1', params=resp.form.submit_fields())
+    assert live_resp.json['result']['2']['items'] == [{'id': '1', 'text': 'foo'}]
+
+    resp.form['f2'].options = []
+    for item in live_resp.json['result']['2']['items']:
+        # simulate javascript filling the <select>
+        resp.form['f2'].options.append((item['id'], False, item['text']))
+
+    # select second field
+    resp.form['f2'] = '1'
+
+    # add block
+    resp = resp.form.submit('f3$add_element')
+    # second field value is kept
+    assert resp.form['f2'].value == '1'
+
+    resp = app.get(formdef.get_url())
+    # select first field
+    resp.form['f1'] = 'foo'
+    live_resp = app.post('/foo/live?modified_field_id=1', params=resp.form.submit_fields())
+    assert live_resp.json['result']['2']['items'] == [{'id': '1', 'text': 'foo'}]
+
+    resp.form['f2'].options = []
+    for item in live_resp.json['result']['2']['items']:
+        # simulate javascript filling the <select>
+        resp.form['f2'].options.append((item['id'], False, item['text']))
+
+    # select second field
+    resp.form['f2'] = '1'
+
+    # submit form with empty value in block
+    resp = resp.form.submit()
+    # second field value is kept
+    assert resp.form['f2'].value == '1'

wcs/forms/root.py

@@ -396,7 +396,7 @@ class FormPage(Directory, FormTemplateMixin):
                 had_prefill = True
         return had_prefill
 
-    def page(self, page, page_change=True, page_error_messages=None, submit_button=None):
+    def page(self, page, page_change=True, page_error_messages=None, submit_button=None, transient_formdata=None):
         displayed_fields = []
 
         session = get_session()
@@ -405,7 +405,10 @@ class FormPage(Directory, FormTemplateMixin):
             magictoken = get_request().form['magictoken']
             self.feed_current_data(magictoken)
 
-        form = self.create_form(page, displayed_fields)
+        with get_publisher().substitutions.temporary_feed(
+                transient_formdata, force_mode='lazy'):
+            form = self.create_form(page, displayed_fields, transient_formdata=transient_formdata)
+
         if submit_button is True:
             # submit_button at True means a non-submitting button has been
             # clicked; details in [ADD_ROW_BUTTON].
@@ -952,7 +955,8 @@ class FormPage(Directory, FormTemplateMixin):
             if form.has_errors() or form.get_submit() is True:
                 return self.page(page, page_change=False,
                         page_error_messages=page_error_messages,
-                        submit_button=form.get_submit())
+                        submit_button=form.get_submit(),
+                        transient_formdata=transient_formdata)
 
             form_data = session.get_by_magictoken(magictoken, {})
             with get_publisher().substitutions.temporary_feed(