make arccache.GetSize return ErrNotFound when not found

arc_cache.go

@@ -88,8 +88,11 @@ func (b *arccache) Has(k cid.Cid) (bool, error) {
 }
 
 func (b *arccache) GetSize(k cid.Cid) (int, error) {
-	if _, blockSize, ok := b.hasCached(k); ok {
-		return blockSize, nil
+	if has, blockSize, ok := b.hasCached(k); ok {
+		if has {
+			return blockSize, nil
+		}
+		return -1, ErrNotFound
 	}
 	blockSize, err := b.blockstore.GetSize(k)
 	if err == ErrNotFound {

arc_cache_test.go

@@ -107,7 +107,7 @@ func TestGetFillsCache(t *testing.T) {
 	if has, err := arc.Has(exampleBlock.Cid()); has || err != nil {
 		t.Fatal("has was true but there is no such block")
 	}
-	if blockSize, err := arc.GetSize(exampleBlock.Cid()); blockSize > -1 || err != nil {
+	if _, err := arc.GetSize(exampleBlock.Cid()); err != ErrNotFound {
 		t.Fatal("getsize was true but there is no such block")
 	}
 
@@ -203,12 +203,11 @@ func TestGetSizeMissingZeroSizeBlock(t *testing.T) {
 	arc.Get(missingBlock.Cid())
 
 	trap("has hit datastore", cd, t)
-	if blockSize, err := arc.GetSize(missingBlock.Cid()); blockSize != -1 || err != nil {
+	if _, err := arc.GetSize(missingBlock.Cid()); err != ErrNotFound {
 		t.Fatal("getsize returned invalid result")
 	}
 }
 
-
 func TestDifferentKeyObjectsWork(t *testing.T) {
 	arc, bs, cd := createStores(t)