Add JSONC and cache support to feature flag service

Author: bobvandevijver

config/packages/drenso_shared.yaml

@@ -45,6 +45,7 @@ drenso_shared:
       enabled: true # Enable the feature flags service and attributes (automatically true when you specify any of the options below and omit this line)
       configuration_file: '' # The JSON file location where your flags are configured, for example '%env(resolve:FEATURES_FILE)%'
       configuration_local_file: '' # Not required, but can be used to override flags in the main configuration file outside of version control
+      json_comment_parser_enabled: true # JSONC supported by default
     gravatar:
       enabled: true # Enable the GravatarHelper for injection (automatically true when you specify any of the options below and omit this line)
       fallback_style: 'mp' # Define a fallback style for accounts without a gravatar, see https://en.gravatar.com/site/implement/images/#default-image

src/DependencyInjection/Configuration.php

@@ -270,6 +270,9 @@ private function configureServices(ArrayNodeDefinition $node): void
                 ->scalarNode('configuration_local_file')
                   ->defaultNull()
                 ->end() // configuration_local_file
+                ->booleanNode('json_comment_parser_enabled')
+                  ->defaultTrue()
+                ->end() // json_comment_parser_enabled
                 ->scalarNode('custom_handler')
                   ->defaultNull()
                 ->end() // custom_handler

src/DependencyInjection/DrensoSharedExtension.php

@@ -290,15 +290,18 @@ private function configureServices(ContainerBuilder $container, array $config, b
   {
     $services = $config['services'];
 
-    if ($services['feature_flags']['enabled']) {
-      if (!$services['feature_flags']['custom_handler']) {
+    $featureFlags = $services['feature_flags'];
+    if ($featureFlags['enabled']) {
+      if (!$featureFlags['custom_handler']) {
         $container
           ->register(FeatureFlagsInterface::class, FeatureFlags::class)
-          ->setArgument('$configuration', $services['feature_flags']['configuration_file'])
-          ->setArgument('$configurationOverride', $services['feature_flags']['configuration_local_file'] ?? '')
+          ->setArgument('$configuration', $featureFlags['configuration_file'])
+          ->setArgument('$configurationOverride', $featureFlags['configuration_local_file'] ?? '')
+          ->setArgument('$jsonCommentParserEnabled', $featureFlags['json_comment_parser_enabled'])
+          ->setArgument('$appCache', new Reference(CacheInterface::class, ContainerInterface::NULL_ON_INVALID_REFERENCE))
           ->setPublic($public);
       } else {
-        $container->setAlias(FeatureFlagsInterface::class, $services['feature_flags']['custom_handler']);
+        $container->setAlias(FeatureFlagsInterface::class, $featureFlags['custom_handler']);
       }
 
       $container

src/FeatureFlags/FeatureFlags.php

@@ -3,12 +3,20 @@
 namespace Drenso\Shared\FeatureFlags;
 
 use Symfony\Component\DependencyInjection\Exception\EnvNotFoundException;
+use Symfony\Contracts\Cache\CacheInterface;
 
 class FeatureFlags implements FeatureFlagsInterface
 {
+  private const CACHE_KEY_MTIME  = 'drenso.feature_flags.mtime';
+  private const CACHE_KEY_CONFIG = 'drenso.feature_flags.configuration';
+
   private ?array $resolvedConfiguration = null;
 
-  public function __construct(private readonly string $configuration, private readonly string $configurationOverride)
+  public function __construct(
+    private readonly string $configuration,
+    private readonly string $configurationOverride,
+    private readonly bool $jsonCommentParserEnabled,
+    private readonly ?CacheInterface $appCache = null)
   {
   }
 
@@ -31,26 +39,68 @@ public function getFlagValue(string $flag): bool
   private function resolve(): void
   {
     if (null !== $this->resolvedConfiguration) {
+      // Configuration already resolved, direct return
       return;
     }
 
     if (!file_exists($this->configuration) || !is_readable($this->configuration)) {
       throw new EnvNotFoundException(sprintf('Could not find features file %s', $this->configuration));
     }
 
+    $overrideAvailable = true;
     if (!$this->configurationOverride
         || !file_exists($this->configurationOverride)
         || !is_readable($this->configurationOverride)) {
       // No need to throw, as it is an override. Do set an empty default value here.
-      $configurationOverride = '{}';
-    } else {
-      $configurationOverride = file_get_contents($this->configurationOverride) ?? '{}';
+      $overrideAvailable = false;
+    }
+
+    if (!$this->appCache) {
+      $this->resolvedConfiguration = $this->parseConfiguration($overrideAvailable);
+
+      return;
     }
 
-    $configuration               = file_get_contents($this->configuration) ?? '{}';
-    $this->resolvedConfiguration = array_merge(
+    // Validate modify times
+    $currentMTime = max(
+      filemtime($this->configuration),
+      $overrideAvailable ? filemtime($this->configurationOverride) : 0,
+    );
+
+    $cachedMTime = $this->appCache->get(self::CACHE_KEY_MTIME, static fn (): int => 0);
+    if ($cachedMTime < $currentMTime) {
+      // Remove cached values as one of the files has been modified
+      $this->appCache->delete(self::CACHE_KEY_MTIME);
+      $this->appCache->delete(self::CACHE_KEY_CONFIG);
+    }
+
+    // Populate the cache
+    $this->resolvedConfiguration = $this->appCache
+      ->get(self::CACHE_KEY_CONFIG, fn (): array => $this->parseConfiguration($overrideAvailable));
+    $this->appCache->get(self::CACHE_KEY_MTIME, static fn (): int => $currentMTime);
+  }
+
+  private function parseConfiguration(bool $overrideAvailable): array
+  {
+    $configuration         = file_get_contents($this->configuration);
+    $configurationOverride = $overrideAvailable ? file_get_contents($this->configurationOverride) : false;
+
+    $configuration         = $configuration ? $this->filterComments($configuration) : '{}';
+    $configurationOverride = $configurationOverride ? $this->filterComments($configurationOverride) : '{}';
+
+    return array_merge(
       json_decode($configuration, true, flags: JSON_THROW_ON_ERROR),
       json_decode($configurationOverride, true, flags: JSON_THROW_ON_ERROR),
     );
   }
+
+  private function filterComments(string $data): string
+  {
+    if (!$this->jsonCommentParserEnabled) {
+      return $data;
+    }
+
+    // Regex from https://stackoverflow.com/a/43439966
+    return preg_replace('~ (" (?:\\\\. | [^"])*+ ") | // \V*+ | /\* .*? \*/ ~xs', '$1', $data);
+  }
 }