closure approach

cmd/utils/cmd.go

@@ -276,6 +276,7 @@ func ImportHistory(chain *core.BlockChain, dir string, network string, from func
 	)
 
 	for i, file := range entries {
+		err := func() error {
 			path := filepath.Join(dir, file)
 
 			// Validate against checksum file in directory.
@@ -283,29 +284,29 @@ func ImportHistory(chain *core.BlockChain, dir string, network string, from func
 			if err != nil {
 				return fmt.Errorf("open %s: %w", path, err)
 			}
+			defer f.Close()
+
 			h := sha256.New()
 			if _, err := io.Copy(h, f); err != nil {
-			f.Close()
 				return fmt.Errorf("checksum %s: %w", path, err)
 			}
 			got := common.BytesToHash(h.Sum(nil)).Hex()
 			if got != checksums[i] {
-			f.Close()
 				return fmt.Errorf("%s checksum mismatch: have %s want %s", file, got, checksums[i])
 			}
 			if _, err := f.Seek(0, io.SeekStart); err != nil {
-			f.Close()
 				return fmt.Errorf("seek %s: %w", path, err)
 			}
 
+			// Import all block data from Era1.
 			e, err := from(f)
 			if err != nil {
-			f.Close() // onedb.From does not close on metadata errors
 				return fmt.Errorf("error opening era: %w", err)
 			}
+			defer e.Close()
+
 			it, err := e.Iterator()
 			if err != nil {
-			e.Close()
 				return fmt.Errorf("error creating iterator: %w", err)
 			}
 
@@ -337,7 +338,6 @@ func ImportHistory(chain *core.BlockChain, dir string, network string, from func
 			for it.Next() {
 				block, err := it.Block()
 				if err != nil {
-				e.Close()
 					return fmt.Errorf("error reading block %d: %w", it.Number(), err)
 				}
 				if block.Number().BitLen() == 0 {
@@ -345,27 +345,22 @@ func ImportHistory(chain *core.BlockChain, dir string, network string, from func
 				}
 				receipts, err := it.Receipts()
 				if err != nil {
-				e.Close()
 					return fmt.Errorf("error reading receipts %d: %w", it.Number(), err)
 				}
 				blocks = append(blocks, block)
 				receiptsList = append(receiptsList, receipts)
 				if len(blocks) == importBatchSize {
 					if err := flush(); err != nil {
-					e.Close()
 						return err
 					}
 				}
 			}
 			if err := it.Error(); err != nil {
-			e.Close()
 				return err
 			}
-		if err := flush(); err != nil {
-			e.Close()
-			return err
-		}
-		if err := e.Close(); err != nil {
+			return flush()
+		}()
+		if err != nil {
 			return err
 		}
 	}