Convert form_set_error() in FormBase classes to use FormErrorInterface

FormBase::setFormError() proxies through to FormErrorInterface::setErrorByName()

What's the reason for "hiding" the method name (setErrorByName())? Are we not proud of it or something? :)

What's the reason for "hiding" the method name (setErrorByName())? Are we not proud of it or something? :)

I like the fact that this potentially makes it more decoupled.

Why don't you use the dependency injection? I created a patch that does this after rerolling your patch.

Added a interdiff of the merge conflicts and a interdiff with the changes of the dependency injection.

+++ b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldEditForm.php
@@ -172,7 +172,7 @@ public function validateForm(array &$form, array &$form_state) {
-      form_error($form['field']['cardinality_container']['cardinality_number'], $form_state, $this->t('Number of values is required.'));
+      $this->setFormError('field][cardinality_number', $form_state, $this->t('Number of values is required.'));

Umm is it correct?

1. +++ b/core/lib/Drupal/Core/Form/FormBase.php
   @@ -214,4 +221,33 @@ protected function container() {
   +   * @param string $name
   

   It can also be NULL

2. +++ b/core/lib/Drupal/Core/Form/FormBase.php
   @@ -214,4 +221,33 @@ protected function container() {
   +   *   The name of the form element.
   

   Perhaps little more description explaining that what can be used as name.

Thanks for the fixes. It is a simple patch nothing else to complain so RTBC.

Committed 560e5af and pushed to 8.x. Thanks!

Summary

• Classes that inherit from (extend) FormBase and its children now use the protected function setFormError instead of form_set_error()
• The new function accepts the same arguments as were used previously: the name of the form element (string $name), an associative array containing the current state of the form (array $form_state) and an optional message to show to the user( string $message)
• For example in FeedFormController.php:

Before

<?php
class FeedFormController extends ContentEntityFormController {
     $result = $feed_storage_controller->getFeedDuplicates($feed);
     foreach ($result as $item) {
       if (strcasecmp($item->title, $feed->label()) == 0) {
        form_set_error('title', $form_state, $this->t('A feed named %feed already exists. Enter a unique title.', array('%feed' => $feed->label())));
       }
       if (strcasecmp($item->url, $feed->url->value) == 0) {
        form_set_error('url', $form_state, $this->t('A feed with this URL %url already exists. Enter a unique URL.', array('%url' => $feed->url->value)));
       }
     }
     parent::validate($form, $form_state);
?>

After

<?php
class FeedFormController extends ContentEntityFormController {
     $result = $feed_storage_controller->getFeedDuplicates($feed);
     foreach ($result as $item) {
       if (strcasecmp($item->title, $feed->label()) == 0) {
        $this->setFormError('title', $form_state, $this->t('A feed named %feed already exists. Enter a unique title.', array('%feed' => $feed->label())));
       }
       if (strcasecmp($item->url, $feed->url->value) == 0) {

        $this->setFormError('url', $form_state, $this->t('A feed with this URL %url already exists. Enter a unique URL.', array('%url' => $feed->url->value)));
       }
     }
     parent::validate($form, $form_state);
?>

Created change notice comment.

Thanks @jonreid! In the code samples I'm not sure if having the class declaration is useful, but I would definitely show that the code is in the validateForm method, and perhaps seek out a shorter example.

Thanks @jonreid and @Cottser! Tagging "Missing change record", as completing the change record updates here blocks a beta: #2083415: [META] Write up all outstanding change notices before release We can even use the new change record draft feature to iterate on it. :)

Yay! Created my first draft change record: https://drupal.org/node/2186135

Revisions welcome, publish it when it's good to go :)

Thanks again @jonreid!

Looks great to me! Published.