Missing default access for all taxonomy term fields

Maybe commit this issue #2015687: Convert field type to FieldType plugin for taxonomy module firstly?

I think the only relevant field here is changed, which I've now implemented by default. We could consider to rely on the read only flag here in an even more generic way? but that might not work as expected?

Ups.

Solving it, would solve this issue as well though - thus I'm not sure it makes sense to do this as an intermediate step then?

It would, but I'm not sure how fast we can do that. And solving this issue would allow us to close two criticals. This and the meta issue.

+++ b/core/lib/Drupal/Core/Field/ChangedFieldItemList.php
@@ -0,0 +1,25 @@
+/**
+ * @file
+ * Contains \Drupal\Core\Field\ChangedFieldItemList.
+ */
+
+namespace Drupal\Core\Field;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * Defines a item list class for changed fields.
+ */
+class ChangedFieldItemList extends FieldItemList {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultAccess($operation = 'view', AccountInterface $account = NULL) {
+    // It is not possible to edit the changed field.
+    return AccessResult::allowedIf($operation !== 'edit');
+  }
+}

There was one issue from tstoeckler that $entity->changed() cannot be set from migrate (afaik this did not went it yet). It is a bit odd to check for edit, given that there might be way more possible operations which also change the entity somehow?

@dawehner: Code always has the option to ignore access rules. It is an opt-in check that is used for things like widgets/formatters, rest, rules UI, .. all of those should never be able to edit/change the changed date.

I think this code is fine, but here is a small question on top.

1. +++ b/core/lib/Drupal/Core/Field/ChangedFieldItemList.php
   @@ -0,0 +1,25 @@
   +class ChangedFieldItemList extends FieldItemList {
   

   Is there a reason why you don't have a NotEditableFieldItemList, can we set a dedicated list class per base field definition?

2. +++ b/core/lib/Drupal/Core/Field/ChangedFieldItemList.php
   @@ -0,0 +1,25 @@
   +  public function defaultAccess($operation = 'view', AccountInterface $account = NULL) {
   +    // It is not possible to edit the changed field.
   +    return AccessResult::allowedIf($operation !== 'edit');
   

   this is on a user level ... so yeah we can still the API evel.

The issue summary and the patch don't seem to match.

Updated the issue summary.

It's just missing the proposed solution/explanation of what the patch does IMHO.

This issue addresses a critical bug and is allowed per https://www.drupal.org/core/beta-changes. Committed 6ee87bc and pushed to 8.0.x. Thanks!