forms: do not keep empty values when parsing ComputedExpressionWidget (#31823)

tests/test_admin_pages.py

@@ -2688,7 +2688,12 @@ def test_workflows_edit_sms_action(pub):
     resp = resp.form.submit().follow()
 
     resp = resp.click('SMS')
-    resp = resp.form.submit()
+    resp = resp.form.submit('to$add_element')
+    resp = resp.form.submit('to$add_element')
+    resp = resp.form.submit('to$add_element')
+    resp.form['to$element1$value_text'] = '12345'
+    resp = resp.form.submit('submit')
+    assert Workflow.get(workflow.id).possible_status[0].items[0].to == ['12345']
 
 def test_workflows_edit_display_form_action(pub):
     create_superuser(pub)

tests/test_widgets.py

@@ -514,6 +514,12 @@ def test_computed_expression_widget():
     assert widget.parse() == 'hello world'
     assert not widget.has_error()
 
+    widget = ComputedExpressionWidget('test')
+    form = MockHtmlForm(widget)
+    mock_form_submission(req, widget, {'test$value_text': '', 'test$type': ['text']})
+    assert widget.parse() == None
+    assert not widget.has_error()
+
     widget = ComputedExpressionWidget('test')
     mock_form_submission(req, widget, {'test$value_python': 'hello world', 'test$type': ['python']})
     assert widget.has_error()

wcs/qommon/form.py

@@ -2366,9 +2366,9 @@ class ComputedExpressionWidget(CompositeWidget):
         if not self.get('type'):
             return
         value_type = self.get('type')
-        value_content = self.get('value_%s' % value_type) or ''
+        value_content = self.get('value_%s' % value_type)
         if value_type == 'python':
-            self.value = '=' + value_content
+            self.value = '=' + (value_content or '')
         else:
             self.value = value_content
         if self.value: