Only print stats when --stats flag is passed

This applies to both text and json output encoings.

- Stats data is now contained within a Stats datastructure
- Stats are printed after root so that first line of output is the same as previously, even when stats are output using --stats

core/commands/dag/dag.go

@@ -16,9 +16,10 @@ import (
 )
 
 const (
+	pinRootsOptionName = "pin-roots"
 	progressOptionName = "progress"
 	silentOptionName   = "silent"
-	pinRootsOptionName = "pin-roots"
+	statsOptionName    = "stats"
 )
 
 // DagCmd provides a subset of commands for interacting with ipld dag objects
@@ -53,10 +54,14 @@ type ResolveOutput struct {
 	RemPath string
 }
 
+type CarImportStats struct {
+	BlockCount uint64
+}
+
 // CarImportOutput is the output type of the 'dag import' commands
 type CarImportOutput struct {
-	BlockCount *uint64   `json:",omitempty"`
-	Root       *RootMeta `json:",omitempty"`
+	Root  *RootMeta       `json:",omitempty"`
+	Stats *CarImportStats `json:",omitempty"`
 }
 
 // RootMeta is the metadata for a root pinning response
@@ -195,8 +200,9 @@ Maximum supported CAR version: 1
 		cmds.FileArg("path", true, true, "The path of a .car file.").EnableStdin(),
 	},
 	Options: []cmds.Option{
-		cmds.BoolOption(silentOptionName, "No output."),
 		cmds.BoolOption(pinRootsOptionName, "Pin optional roots listed in the .car headers after importing.").WithDefault(true),
+		cmds.BoolOption(silentOptionName, "No output."),
+		cmds.BoolOption(statsOptionName, "Output stats."),
 	},
 	Type: CarImportOutput{},
 	Run:  dagImport,
@@ -208,16 +214,19 @@ Maximum supported CAR version: 1
 				return nil
 			}
 
-			// event should have only one of `Root` or `BlockCount` set, not both
+			// event should have only one of `Root` or `Stats` set, not both
 			if event.Root == nil {
-				if event.BlockCount == nil {
+				if event.Stats == nil {
 					return fmt.Errorf("Unexpected message from DAG import")
 				}
-				fmt.Fprintf(w, "Imported %d blocks\n", *event.BlockCount)
+				stats, _ := req.Options[statsOptionName].(bool)
+				if stats {
+					fmt.Fprintf(w, "Imported %d blocks\n", event.Stats.BlockCount)
+				}
 				return nil
 			}
 
-			if event.BlockCount != nil {
+			if event.Stats != nil {
 				return fmt.Errorf("Unexpected message from DAG import")
 			}
 

core/commands/dag/import.go

@@ -55,10 +55,6 @@ func dagImport(req *cmds.Request, res cmds.ResponseEmitter, env cmds.Environment
 		return done.err
 	}
 
-	if err := res.Emit(&CarImportOutput{BlockCount: &done.blockCount}); err != nil {
-		return err
-	}
-
 	// It is not guaranteed that a root in a header is actually present in the same ( or any )
 	// .car file. This is the case in version 1, and ideally in further versions too
 	// Accumulate any root CID seen in a header, and supplement its actual node if/when encountered
@@ -119,6 +115,17 @@ func dagImport(req *cmds.Request, res cmds.ResponseEmitter, env cmds.Environment
 		}
 	}
 
+	stats, _ := req.Options[statsOptionName].(bool)
+	if stats {
+		if err := res.Emit(&CarImportOutput{
+			Stats: &CarImportStats{
+				BlockCount: done.blockCount,
+			},
+		}); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }