Issue #3415582 by nico.b, larowlan, Matt B: Unhandled exception when trying to...

Issue #3415582 by nico.b, larowlan, Matt B: Unhandled exception when trying to register a duplicate username with different case

core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/UniqueFieldValueValidator.php

@@ -82,7 +82,7 @@ public function validate($items, Constraint $constraint) {
       // If our entity duplicates field values in any other entity, the query
       // will return all field values that belong to those entities. Narrow
       // down to only the specific duplicate values.
-      $duplicate_values = array_intersect($item_values, $other_entity_values);
+      $duplicate_values = $this->caseInsensitiveArrayIntersect($item_values, $other_entity_values);
 
       foreach ($duplicate_values as $delta => $dupe) {
         $violation = $this->context
@@ -112,6 +112,26 @@ public function validate($items, Constraint $constraint) {
     }
   }
 
+  /**
+   * Perform a case-insensitive array intersection, but keep original capitalization.
+   *
+   * @param array $orig_values
+   *   The original values to be returned.
+   * @param array $comp_values
+   *   The values to intersect $orig_values with.
+   *
+   * @return array
+   *   Elements of $orig_values contained in $comp_values when ignoring capitalization.
+   */
+  private function caseInsensitiveArrayIntersect(array $orig_values, array $comp_values): array {
+    $lowercase_comp_values = array_map('strtolower', $comp_values);
+    $intersect_map = array_map(fn (string $x) => in_array(strtolower($x), $lowercase_comp_values, TRUE) ? $x : NULL, $orig_values);
+
+    return array_filter($intersect_map, function ($x) {
+      return $x !== NULL;
+    });
+  }
+
   /**
    * Get an array of duplicate field values.
    *

core/tests/Drupal/KernelTests/Core/Validation/UniqueValuesConstraintValidatorTest.php

@@ -288,4 +288,42 @@ public function testValidationMultiple() {
 
   }
 
+  /**
+   * Tests the UniqueField validation constraint validator with regards to case-insensitivity.
+   *
+   * Case 5. Try to create another entity with existing value for unique field with different capitalization.
+   *
+   * @throws \Drupal\Core\Entity\EntityStorageException
+   *
+   * @covers ::validate
+   */
+  public function testValidationCaseInsensitive(): void {
+    // Create entity with two values for the testing field.
+    $definition = [
+      'id' => (int) rand(0, getrandmax()),
+      'user_id' => 0,
+      'field_test_text' => [
+        'text1',
+        'text2',
+      ],
+    ];
+    $entity = EntityTestUniqueConstraint::create($definition);
+    $entity->save();
+
+    // Create another entity with two values for the testing field, one identical
+    // to other value, but with different capitalization which should still trigger a validation error.
+    $definition = [
+      'id' => (int) rand(0, getrandmax()),
+      'user_id' => 0,
+      'field_test_text' => [
+        'Text1',
+        'text3',
+      ],
+    ];
+    $entity = EntityTestUniqueConstraint::create($definition);
+    $violations = $entity->validate();
+    $this->assertCount(1, $violations);
+    $this->assertEquals('field_test_text.0', $violations[0]->getPropertyPath());
+  }
+
 }