Only allow machine like names for the field alias row plugin

Rerolled, and also just removed the passing by reference in the validation method signature. Would do an interdiff by this is just one character/line :) Although the serialization would handle any of these characters that aren't allowed, consistency is better for sure.

Anything to excise these crazy random test failures is a win IMO, So Happy with this patch.

+    if (preg_match('@[^A-Za-z0-9_-]+@', $element['#value'])) {
...
+    // 32 to 64 is part of this::randomString() but not this::randomName() so
+    // this will be an invalid character.

32-64 includes 0-9 and - (48).

+++ b/core/modules/rest/lib/Drupal/rest/Plugin/views/row/DataFieldRow.php
@@ -82,12 +82,22 @@ public function buildOptionsForm(&$form, &$form_state) {
   /**
+   * Form element validation handler for \Drupal\rest\Plugin\views\row\DataFieldRow::buildOptionsForm().
+   */
+  public function validateAliasName($element, &$form_state) {
+    if (preg_match('@[^A-Za-z0-9_-]+@', $element['#value'])) {
+      form_error($element, t('The machine-readable name must contain only letters, numbers, dashes and underscores.'));
+    }

There is no validation function already for that in core? We cannot use form_validate_machine_name(), but is there nothing else? I suggest you add element_validate_machine_name() to form.inc.

+++ b/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
@@ -174,11 +176,17 @@ public function testUIFieldAlias() {
+    // 91 to 96 is part of this::randomString() but not this::randomName() so
+    // this will be an invalid character.
+    $random_name_2 = chr(rand(91, 96)) . $this->randomName();

$random_name_2 is a bad variable name, use $invalid_name instead?

_ = 95. Thanks for clarifying why not only machine name. Why only these characters then? I checked the previous issue but could not crack it.

Ok. Tiny change in range to prevent random failures and we are good.

Yeah, that is much better IMO. I tihnk this is ready again?

Looks reasonable. Committed/pushed to 8.x. Not sure why this was posted as a feature request.

Excuse me, but I need to know if it would be too dangerous for the alias to allow dots [ . ] and colons [ : ].

I'm trying to expose my data in Dublin Core style, and its terms are segemented by dots or double-dots (ex.: dc.title, dc.identifier.uri).