fix: make no-op legacy claims finder comply with interface expectations

pkg/construct/construct.go

@@ -335,7 +335,7 @@
 	// TODO: add sender / publisher / linksystem
 	legacyClaims := cfg.legacyClaims
 	if legacyClaims == nil {
-		legacyClaims = providerindex.NewNotFoundLegacyClaimsFinder()
+		legacyClaims = providerindex.NewNoResultsLegacyClaimsFinder()
 	}
 	providerIndex := providerindex.New(providersCache, findClient, publisher, legacyClaims)
 

pkg/service/providerindex/legacy.go

@@ -26,6 +26,8 @@
 
 // LegacyClaimsFinder is a read-only interface to find claims on a legacy system
 type LegacyClaimsFinder interface {
+	// Find returns a list of claims for a given content hash.
+	// Implementations should return an empty slice and no error if no results are found.
 	Find(ctx context.Context, contentHash multihash.Multihash) ([]model.ProviderResult, error)
 }
 
@@ -260,15 +262,15 @@
 	}, nil
 }
 
-// NotFoundLegacyClaimsFinder is a LegacyClaimsFinder that always returns ErrKeyNotFound. It can be used when accessing
-// claims in a legacy system is not required
-type NotFoundLegacyClaimsFinder struct{}
+// NoResultsLegacyClaimsFinder is a LegacyClaimsFinder that returns no results. It can be used when accessing claims
+// in a legacy system is not required
+type NoResultsLegacyClaimsFinder struct{}
 
-func NewNotFoundLegacyClaimsFinder() NotFoundLegacyClaimsFinder {
-	return NotFoundLegacyClaimsFinder{}
+func NewNoResultsLegacyClaimsFinder() NoResultsLegacyClaimsFinder {
+	return NoResultsLegacyClaimsFinder{}
 }
 
-// Find always returns ErrKeyNotFound
-func (f NotFoundLegacyClaimsFinder) Find(ctx context.Context, contentHash multihash.Multihash) ([]model.ProviderResult, error) {
-	return nil, types.ErrKeyNotFound
+// Find always returns no results
+func (f NoResultsLegacyClaimsFinder) Find(ctx context.Context, contentHash multihash.Multihash) ([]model.ProviderResult, error) {
+	return []model.ProviderResult{}, nil
 }