[Settings] Keep admin settings and config listings usable with a settings-store read target

src/Perspective/Repository/ElementTreeWidgetConfigRepository.php

@@ -147,7 +147,7 @@ function ($key, $data) {
     public function listConfigurations(): array
     {
         $configurations = [];
-        $keys = array_merge(ElementTreeWidgets::values(), $this->getRepository()->fetchAllKeys());
+        $keys = array_merge(ElementTreeWidgets::values(), $this->getConfigurationKeys());
         foreach ($keys as $key) {
             $configurations[] = $this->getConfiguration($key);
         }
@@ -179,6 +179,23 @@ public function deleteConfiguration(
         }
     }
 
+    /**
+     * Only the keys the configured read target can actually load: getConfiguration() reads through
+     * the read target, so listing a key that lives in the other location makes it fail with a not
+     * found error and takes the whole listing down with it. Without a read target both locations
+     * are read, so both sets of keys belong in the listing.
+     *
+     * @throws Exception
+     */
+    private function getConfigurationKeys(): array
+    {
+        $repository = $this->getRepository();
+
+        return $repository->getReadTargets() === []
+            ? $repository->fetchAllKeys()
+            : $repository->fetchAllKeysByReadTargets();
+    }
+
     private function getRepository(): LocationAwareConfigRepository
     {
         if (!$this->repository) {

src/Perspective/Repository/PerspectiveConfigRepository.php

@@ -88,7 +88,7 @@ function ($key, $data) {
     public function listConfigurations(): array
     {
         $configurations = [];
-        foreach ($this->getRepository()->fetchAllKeys() as $key) {
+        foreach ($this->getConfigurationKeys() as $key) {
             $configurations[] = $this->getConfiguration($key);
         }
 
@@ -119,6 +119,23 @@ public function deleteConfiguration(
         }
     }
 
+    /**
+     * Only the keys the configured read target can actually load: getConfiguration() reads through
+     * the read target, so listing a key that lives in the other location makes it fail with a not
+     * found error and takes the whole listing down with it. Without a read target both locations
+     * are read, so both sets of keys belong in the listing.
+     *
+     * @throws Exception
+     */
+    private function getConfigurationKeys(): array
+    {
+        $repository = $this->getRepository();
+
+        return $repository->getReadTargets() === []
+            ? $repository->fetchAllKeys()
+            : $repository->fetchAllKeysByReadTargets();
+    }
+
     private function getRepository(): LocationAwareConfigRepository
     {
         if (!$this->repository) {

src/Setting/Admin/Repository/SettingRepository.php

@@ -77,15 +77,20 @@ private function getRepository(): LocationAwareConfigRepository
      */
     private function loadConfig(): array
     {
-        $data = $this->getRepository()->loadConfigByKey(Configuration::ADMIN_SETTINGS_NODE);
+        [$data, $dataSource] = $this->getRepository()->loadConfigByKey(Configuration::ADMIN_SETTINGS_NODE);
         $loadType = $this->getRepository()->getReadTargets()[0] ?? null;
 
+        // The settings store only holds the admin settings once they have been saved through the UI.
+        // Until then the symfony configuration is their only source, so it has to serve as the
+        // fallback - otherwise configured branding silently disappears as soon as the read target is
+        // switched to the settings store, which is the only way to keep the settings writeable in a
+        // production environment. The data source stays unset: the settings are still written to the
+        // settings store, so they remain writeable.
         if (!$data && $loadType === LocationAwareConfigRepository::LOCATION_SETTINGS_STORE) {
-            $data = $this->adminConfig;
-            $data['writeable'] = $this->isRepositoryWritable();
+            $data = $this->adminConfig[Configuration::ADMIN_SETTINGS_NODE] ?? [];
         }
 
-        return $data;
+        return [$data, $dataSource];
     }
 
     /**