Plugin definitions should store their class in a consistent manner (without leading slashes)

I just corrected the issue title and summary

Do we need a change notice here?

Thanks!

I love that this is consistent now, except for TypedConfig. Whatever the case, definitely an improvement. ++

Eclipse

Note that issues like this should be targeted against 8.4.x, but can be considered for backport once they are committed to that branch. See the updated alpha release policy. Thanks!

@effulgentsia asked to switch from implicit to explicit test coverage.

The changes made to \Drupal\Tests\Core\Plugin\DefaultPluginManagerTest::providerTestProcessDefinition are expliciting testing this with and without slashes using both arrays and PluginDefinition objects.

Thanks! Pushed to 8.4.x and published the CR with the version set to 8.4.x.

Since this is a low-risk, low-disruption patch, I'm open to cherry picking it to 8.3 prior to beta, if this is in fact a "Contributed project soft blocker". But why is it? Please add a comment explaining that and set it to Needs review or RTBC, depending on whether that comment warrants peer review.

+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -63,6 +63,17 @@ protected function getDiscovery() {
+    // Typed config definitions assume a leading slash, see ::hasConfigSchema().
+    if (is_array($definition) && isset($definition['class'])) {
+      $definition['class'] = '\\' . $definition['class'];
+    }

A follow-up to remove this would be great, since I think it should be fine to fix that line in hasConfigSchema() to use Undefined::class.

Never mind. I figured it out. Contrib should be able to compare with Foo::class. Therefore, cherry picked to 8.3.x and updated the CR to be on that version.