src/Controller/ConfigInspectorController.php | 30 +++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/Controller/ConfigInspectorController.php b/src/Controller/ConfigInspectorController.php
index 24fc894..5d5f728 100644
--- a/src/Controller/ConfigInspectorController.php
+++ b/src/Controller/ConfigInspectorController.php
@@ -3,6 +3,7 @@
 namespace Drupal\config_inspector\Controller;
 
 use Drupal\config_inspector\ConfigInspectorManager;
+use Drupal\config_inspector\ConfigSchemaValidatability;
 use Drupal\Core\Config\Schema\ArrayElement;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Controller\ControllerBase;
@@ -133,6 +134,7 @@ class ConfigInspectorController extends ControllerBase {
       '#header' => [
         'name' => $this->t('Configuration key'),
         'schema' => $this->t('Schema'),
+        'validatability' => $this->t('Validatable'),
         'violations' => $this->t('Data'),
         'list' => $this->t('List'),
         'tree' => $this->t('Tree'),
@@ -170,6 +172,7 @@ class ConfigInspectorController extends ControllerBase {
         $schema = $this->t('Correct');
         $result = $this->configInspectorManager->checkValues($name);
         $raw_violations = $this->configInspectorManager->validateValues($name);
+        $raw_validatability = $this->configInspectorManager->checkValidatabilityValues($name);
         if (is_array($result)) {
           // The no-schema case is covered above already, if we got errors, the
           // schema is partial.
@@ -183,6 +186,11 @@ class ConfigInspectorController extends ControllerBase {
               'data-has-errors' => is_array($result),
             ],
           ],
+          'validatability' => [
+            '#markup' => $raw_validatability->isComplete()
+              ? $this->t('Validatable')
+              : $this->t('@validatability%', ['@validatability' => intval($raw_validatability->computePercentage() * 100)]),
+          ],
           'violations' => [
             '#markup' => $raw_violations->count() === 0
               ? $this->t('Valid')
@@ -243,7 +251,8 @@ class ConfigInspectorController extends ControllerBase {
    */
   public function getTree($name) {
     $config_schema = $this->configInspectorManager->getConfigSchema($name);
-    $output = $this->formatTree($config_schema);
+    $validatability = $this->configInspectorManager->checkValidatabilityValues($name);
+    $output = $this->formatTree($config_schema, $validatability);
     $output['#title'] = $this->t('Tree of configuration data for %name', ['%name' => $name]);
     return $output;
   }
@@ -329,6 +338,8 @@ class ConfigInspectorController extends ControllerBase {
     $rows = [];
     // Check compliance with the underlying primitives (string, boolean …).
     $errors = (array) $this->configInspectorManager->checkValues($config_name);
+    // Check validatability (beyond primitives).
+    $raw_validatability = $this->configInspectorManager->checkValidatabilityValues($config_name);
     // Check compliance with the validation constraints, if any.
     $raw_violations = $this->configInspectorManager->validateValues($config_name);
     $violations = ConfigInspectorManager::violationsToArray($raw_violations);
@@ -343,6 +354,9 @@ class ConfigInspectorController extends ControllerBase {
           $key,
           $definition['label'],
           $definition['type'],
+          $raw_validatability->getValidatabilityPerPropertyPath()[$key]
+            ? $this->t('Yes')
+            : $this->t('No'),
           $this->formatValue($element),
           @$errors[$config_name . ':' . $key] ?: '',
           !array_key_exists($key, $violations)
@@ -362,6 +376,7 @@ class ConfigInspectorController extends ControllerBase {
         $this->t('Name'),
         $this->t('Label'),
         $this->t('Type'),
+        $this->t('Validatable'),
         $this->t('Value'),
         $this->t('Error'),
         $this->t('Validation error'),
@@ -375,6 +390,8 @@ class ConfigInspectorController extends ControllerBase {
    *
    * @param array|object $schema
    *   The schema.
+   * @param \Drupal\config_inspector\ConfigSchemaValidatability $validatability
+   *   The associated validatability.
    * @param bool $collapsed
    *   (Optional) Indicates whether the details are collapsed by default.
    * @param string $base_key
@@ -383,28 +400,31 @@ class ConfigInspectorController extends ControllerBase {
    * @return array
    *   The tree in the form of a render array.
    */
-  public function formatTree($schema, $collapsed = FALSE, $base_key = '') {
+  public function formatTree($schema, ConfigSchemaValidatability $validatability, $collapsed = FALSE, $base_key = '') {
     $build = [];
     foreach ($schema as $key => $element) {
       $definition = $element->getDataDefinition();
       $label = $definition['label'] ?: $this->t('N/A');
       $type = $definition['type'];
       $element_key = $base_key . $key;
+      $is_validatable = $validatability->getValidatabilityPerPropertyPath()[$base_key . $key]
+        ? $this->t('validatable')
+        : '<s>' . $this->t('validatable') . '</s>';
       if ($element instanceof ArrayElement) {
         $build[$key] = [
           '#type' => 'details',
           '#title' => $label,
-          '#description' => $element_key . ' (' . $type . ')',
+          '#description' => $element_key . ' (' . $type . ', ' . $is_validatable . ')',
           '#description_display' => 'after',
           '#open' => !$collapsed,
-        ] + $this->formatTree($element, TRUE, $element_key . '.');
+        ] + $this->formatTree($element, $validatability, TRUE, $element_key . '.');
       }
       else {
         $build[$key] = [
           '#type' => 'item',
           '#title' => $label,
           '#plain_text' => $this->formatValue($element),
-          '#description' => $element_key . ' (' . $type . ')',
+          '#description' => $element_key . ' (' . $type . ', ' . $is_validatable . ')',
           '#description_display' => 'after',
         ];
       }