Adjust cache ModuleDataProvider to re-retrieve delegate values from store after putting in store (#3449)

Co-authored-by: bufdev <bufdev-github@buf.build>

Author: doriable

private/bufpkg/bufmodule/bufmodulecache/base_provider.go

@@ -80,6 +80,24 @@ func (p *baseProvider[K, V]) getValuesForKeys(ctx context.Context, keys []K) ([]
 	); err != nil {
 		return nil, err
 	}
+	// We are getting the values again so that we retrieve the values from the cache directly.
+	// This matters for ie ModuleDatas where the storage.Bucket attached will have local paths
+	// instead of empty local paths if read from the cache. We documment NewModuleDataProvider
+	// to return a ModuleDataProvider that will always have local paths for returned storage.Buckets,
+	// if the cache is an on-disk cache.
+	var delegateNotFoundKeys []K
+	delegateValues, delegateNotFoundKeys, err = p.storeGetValuesForKeys(ctx, notFoundKeys)
+	if err != nil {
+		return nil, err
+	}
+	// We need to ensure that all the delegate values can be retrieved from the store. If there
+	// are unfound keys, we return an error.
+	if len(delegateNotFoundKeys) > 0 {
+		return nil, syserror.Newf(
+			"delegate keys %v not found in the store after putting in the store",
+			delegateNotFoundKeys,
+		)
+	}
 
 	p.keysRetrieved.Add(int64(len(keys)))
 	p.keysHit.Add(int64(len(foundValues)))

private/bufpkg/bufmodule/bufmodulecache/module_data_provider.go

@@ -26,6 +26,8 @@ import (
 // NewModuleDataProvider returns a new ModuleDataProvider that caches the results of the delegate.
 //
 // The ModuleDataStore is used as a cache.
+//
+// All files in returned [storage.Bucket]s will have local paths if the cache is on-disk.
 func NewModuleDataProvider(
 	logger *slog.Logger,
 	delegate bufmodule.ModuleDataProvider,