DefaultContent Finder fails with ImportException on non-entity .json files in content directory

Generated with the help of an LLM.

Problem/Motivation

In #3532950: Support importing default content in JSON format, \Drupal\Core\DefaultContent\Finder was updated to discover and import default content entities defined in JSON format in addition to YAML. To do so, Finder scans the recipe's content/ directory for both *.yml and *.json files.

When default content includes file entities, the physical file payloads associated with the entities are stored inside content/file/{filename} alongside the entity definition file (as exported by \Drupal\Core\DefaultContent\Exporter::exportToFile() and \Drupal\file\EventSubscriber\DefaultContentSubscriber).

If the physical file payload is a JSON document (such as an OpenAPI / OAS specification file like petstore.json, a GeoJSON file, or a JSON schema fixture), Finder::__construct() encounters the .json file during directory traversal and assumes it is an exported Drupal content entity. Because the document is a raw JSON asset and not a normalized default content export, it lacks a _meta.uuid key, causing Finder to throw an ImportException:

In Finder.php line 57:

  /path/to/recipe/content/file/petstore.json does not have a UUID.

This regression prevents recipes containing default file entities with .json assets from being applied.

Steps to reproduce

1. Create a recipe containing default content for a file entity whose physical asset is a .json file (e.g. content/file/petstore.json accompanying content/file/{uuid}.yml).
2. Apply the recipe via recipe:apply, drush recipe, or within a test using RecipeTestTrait::applyRecipe().
3. Observe the failure: ImportException: .../content/file/petstore.json does not have a UUID.

Proposed resolution

In \Drupal\Core\DefaultContent\Finder::__construct(), do not require every discovered .json or .yml file to be a content entity. If a decoded file is not an array or does not contain _meta, it represents a non-entity file asset (or unrelated file) and should be skipped by Finder:

foreach ($finder as $file) {
  $decoded = (match ($file->getExtension()) {
    Yaml::getFileExtension() => Yaml::decode(...),
    Json::getFileExtension() => Json::decode(...),
  })($file->getContents());

  // Physical file attachments or non-entity files do not have default content metadata.
  if (!is_array($decoded) || !isset($decoded['_meta'])) {
    continue;
  }

  $decoded['_meta']['path'] = $file->getPathname();
  $uuid = $decoded['_meta']['uuid'] ?? throw new ImportException($decoded['_meta']['path'] . ' does not have a UUID.');
  $files[$uuid] = $decoded;

Files that do define _meta but lack a uuid will continue to throw an ImportException, preserving existing validation coverage in \Drupal\Tests\Core\DefaultContent\FinderTest::testExceptionIfNoUuid().

Remaining tasks

• Create a merge request.
• Add unit and functional test coverage for recipes with default content file entities attaching .json files.
• Review and commit.

User interface changes

None.

Introduced terminology

None.

API changes

\Drupal\Core\DefaultContent\Finder ignores files without _meta rather than throwing an ImportException.

Data model changes

None.

Release notes snippet