tests/admin_pages/test_form.py

@@ -3589,6 +3589,44 @@ def test_form_new_computed_field(pub):
     assert resp.form['data_source$type'].options == [('None', True, 'None'), ('carddef:baz', False, 'Baz')]
 
 
+def test_form_edit_computed_field(pub):
+    create_superuser(pub)
+    create_role(pub)
+
+    FormDef.wipe()
+    formdef = FormDef()
+    formdef.name = 'form title'
+    formdef.fields = []
+    formdef.store()
+
+    app = login(get_app(pub))
+    resp = app.get('/backoffice/forms/1/')
+    resp = resp.click(href='fields/')
+
+    resp.forms[0]['label'] = 'foobar'
+    resp.forms[0]['type'] = 'computed'
+    resp = resp.forms[0].submit().follow()
+    field = FormDef.get(1).fields[0]
+
+    resp = app.get('/backoffice/forms/%s/fields/%s/' % (formdef.id, field.id))
+    assert resp.pyquery('input#form_value_template').attr.size == '150'
+    resp.form['value_template'] = '{% with %}'  # invalid syntax
+    resp = resp.form.submit('submit')
+    assert 'syntax error' in resp.pyquery('#form_error_value_template').text()
+
+    resp.form['value_template'] = '{{ "%s" }}' % ('xxxx ' * 200)  # long string
+    resp = resp.form.submit('submit')
+
+    # check a long template value is displayed in a textarea
+    resp = app.get('/backoffice/forms/%s/fields/%s/' % (formdef.id, field.id))
+    assert resp.pyquery('textarea#form_value_template').attr.rows == '7'
+
+    # check template validation is still effective
+    resp.form['value_template'] = '{% with %}'  # invalid syntax
+    resp = resp.form.submit('submit')
+    assert 'syntax error' in resp.pyquery('#form_error_value_template').text()
+
+
 def test_form_category_management_roles(pub, backoffice_user, backoffice_role):
     app = login(get_app(pub), username='backoffice-user', password='backoffice-user')
     app.get('/backoffice/forms/', status=403)

wcs/fields.py

@@ -4374,15 +4374,20 @@ class ComputedField(Field):
             size=30,
             hint=_('This is used as suffix for variable names.'),
         )
+        value_widget = StringWidget
+        value_widget_kwargs = {'size': 150}
+        if len(self.value_template or '') > value_widget_kwargs['size']:
+            value_widget = TextWidget
+            value_widget_kwargs = {'cols': 150, 'rows': len(self.value_template) // 150 + 1}
         form.add(
-            StringWidget,
+            value_widget,
             'value_template',
             title=_('Value'),
             required=True,
-            size=80,
             value=self.value_template,
             validation_function=ComputedExpressionWidget.validate_template,
             hint=_('As a Django template'),
+            **value_widget_kwargs,
         )
         form.add(
             CheckboxWidget,