fix(arc): return the correct size when only "has" is cached

arc_cache.go

@@ -86,10 +86,15 @@ func (b *arccache) Has(k cid.Cid) (bool, error) {
 
 func (b *arccache) GetSize(k cid.Cid) (int, error) {
 	if has, blockSize, ok := b.hasCached(k); ok {
-		if has {
+		if !has {
+			// don't have it, return
+			return -1, ErrNotFound
+		}
+		if blockSize >= 0 {
+			// have it and we know the size
 			return blockSize, nil
 		}
-		return -1, ErrNotFound
+		// we have it but don't know the size, ask the datastore.
 	}
 	blockSize, err := b.blockstore.GetSize(k)
 	if err == ErrNotFound {

arc_cache_test.go

@@ -123,7 +123,7 @@ func TestGetFillsCache(t *testing.T) {
 		t.Fatal("has returned invalid result")
 	}
 	if blockSize, err := arc.GetSize(exampleBlock.Cid()); blockSize == -1 || err != nil {
-		t.Fatal("getsize returned invalid result")
+		t.Fatal("getsize returned invalid result", blockSize, err)
 	}
 }
 
@@ -185,6 +185,25 @@ func TestGetSizeAfterSucessfulGetIsCached(t *testing.T) {
 	arc.GetSize(exampleBlock.Cid())
 }
 
+func TestGetSizeAfterSucessfulHas(t *testing.T) {
+	arc, bs, _ := createStores(t)
+
+	bs.Put(exampleBlock)
+	has, err := arc.Has(exampleBlock.Cid())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !has {
+		t.Fatal("expected to have block")
+	}
+
+	if size, err := arc.GetSize(exampleBlock.Cid()); err != nil {
+		t.Fatal(err)
+	} else if size != len(exampleBlock.RawData()) {
+		t.Fatalf("expected size %d, got %d", len(exampleBlock.RawData()), size)
+	}
+}
+
 func TestGetSizeMissingZeroSizeBlock(t *testing.T) {
 	arc, bs, cd := createStores(t)
 	emptyBlock := blocks.NewBlock([]byte{})