Edit Media Library widget produces "This value should not be null" wrong error when field is required

Just a straight re-roll for 9.2.x

Adding some tags for DrupalCon NA which is happening April 12-16 virtually.

Can steps to reproduce/test/validation be added to the summary?

I tagged this issue novice in hopes that a new contributor could work on this, thanks.

Updated summary.

Applied patch #3 and it works fine.The error message is showing correctly with the field name after applying this patch.

Before patch:

After patch:

RTBC +1

Tested patch and works as expected with correct error message, "Media content field is required."

+++ b/core/modules/media_library/tests/src/Functional/FieldWidgetTest.php
@@ -0,0 +1,65 @@
+    $this->drupalGet("/node/add/$node_type");
+    $this->getSession()->getPage()->pressButton('Save');
+    $this->assertSession()->pageTextNotContains('This value should not be null');
+  }

We should add a positive assertion here for the text we actually expect to get, otherwise there's no guarantee we're getting a validation message at all.

@catch , I have rerolled and modified the patch. I have replaced pageTextNotContains with pageTextContains assertion.

Thanks.

Verified and tested patch #12.
Patch applied successfully and looks good to me.

Testing Steps:
# Goto: Extend -> Enable the Media Library and Media modules.
# Create the content type with the Media Library field and make it a required field
# Create the new content type using the Media Library field and save it.
# User is able to see a wrong error message, "This value should not be null"

Expected Results:
# User should see the message like "Media field is required"

Actual Results:
# User is able to see a wrong error message, "This value should not be null"

Can be a move to RTBC.

+++ b/core/modules/media_library/src/Plugin/Field/FieldWidget/MediaLibraryWidget.php
@@ -939,4 +942,34 @@ protected static function setFieldState(array $element, FormStateInterface $form
+
+    // Trigger error if the field is required and no media is present.
+    // Although the Form API's default validation would also catch this, the
+    // validation error message is too vague, so a more precise one is
+    // provided here.
+    $selection_count = !empty($element['selection']) ? count(Element::children($element['selection'])) : 0;
+    if (empty($media) && $selection_count === 0 && !empty($element['#required'])) {
+      $form_state->setError($element, new TranslatableMarkup('@name field is required.',
+        ['@name' => $element['#title']]));
+      return;
+    }
+  }

This feels like it shouldn't be necessary. Is there a reason we can't use the browser's own required form element feature? Going to tag for subsystem maintainer review.

Also feel like 'The value should not be null' isn't really good for any situation, so what about changing the default message itself?

Rerolled patch 12 for Drupal 9.5

Tried to re-roll patch #12 for 11.x-dev.

Did not test but was previously tagged for issue summary update which still looks like needs to be done.