Switch ipfs dag get to serialize to an IPLD-Prime codec and output …

…in the same way as `ipfs cat`

core/commands/dag/dag.go

@@ -108,6 +108,9 @@ format.
 	Arguments: []cmds.Argument{
 		cmds.StringArg("ref", true, false, "The object to get").EnableStdin(),
 	},
+	Options: []cmds.Option{
+		cmds.StringOption("format", "f", "Format that the object will be serialized as.").WithDefault("dag-json"),
+	},
 	Run: dagGet,
 }
 

core/commands/dag/get.go

@@ -1,11 +1,19 @@
 package dagcmd
 
 import (
-	"strings"
+	"fmt"
+	"io"
+	"strconv"
 
 	"github.com/ipfs/go-ipfs/core/commands/cmdenv"
+	ipldlegacy "github.com/ipfs/go-ipld-legacy"
 	"github.com/ipfs/interface-go-ipfs-core/path"
 
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/multicodec"
+	"github.com/ipld/go-ipld-prime/traversal"
+	mc "github.com/multiformats/go-multicodec"
+
 	cmds "github.com/ipfs/go-ipfs-cmds"
 )
 
@@ -15,6 +23,16 @@ func dagGet(req *cmds.Request, res cmds.ResponseEmitter, env cmds.Environment) e
 		return err
 	}
 
+	format, _ := req.Options["format"].(string)
+	fCodec, ok := mc.Of(format)
+	if !ok {
+		n, err := strconv.Atoi(format)
+		if err != nil {
+			return fmt.Errorf("%s is not a valid codec name", format)
+		}
+		fCodec = mc.Code(n)
+	}
+
 	rp, err := api.ResolvePath(req.Context, path.New(req.Arguments[0]))
 	if err != nil {
 		return err
@@ -25,14 +43,34 @@ func dagGet(req *cmds.Request, res cmds.ResponseEmitter, env cmds.Environment) e
 		return err
 	}
 
-	var out interface{} = obj
+	universal, ok := obj.(ipldlegacy.UniversalNode)
+	if !ok {
+		return fmt.Errorf("%T is not a valid IPLD node", obj)
+	}
+
+	finalNode := universal.(ipld.Node)
+
 	if len(rp.Remainder()) > 0 {
-		rem := strings.Split(rp.Remainder(), "/")
-		final, _, err := obj.Resolve(rem)
+		remainderPath := ipld.ParsePath(rp.Remainder())
+
+		finalNode, err = traversal.Get(finalNode, remainderPath)
 		if err != nil {
 			return err
 		}
-		out = final
 	}
-	return cmds.EmitOnce(res, &out)
+
+	encoder, err := multicodec.LookupEncoder(uint64(fCodec))
+	if err != nil {
+		return fmt.Errorf("invalid encoding: %s - %s", format, err)
+	}
+
+	r, w := io.Pipe()
+	go func() {
+		defer w.Close()
+		if err := encoder(finalNode, w); err != nil {
+			res.CloseWithError(err)
+		}
+	}()
+
+	return res.Emit(r)
 }

go.mod

@@ -45,7 +45,7 @@ require (
 	github.com/ipfs/go-ipld-cbor v0.0.5
 	github.com/ipfs/go-ipld-format v0.2.0
 	github.com/ipfs/go-ipld-git v0.0.4-0.20210326054912-6be33ddcbecc
-	github.com/ipfs/go-ipld-legacy v0.0.0-20210312014519-2895f54096d5
+	github.com/ipfs/go-ipld-legacy v0.0.0-20210325015318-9799f2cffab0
 	github.com/ipfs/go-ipns v0.0.2
 	github.com/ipfs/go-log v1.0.4
 	github.com/ipfs/go-merkledag v0.3.3-0.20210325015807-e952d22343f9
@@ -57,7 +57,7 @@ require (
 	github.com/ipfs/go-unixfs v0.2.4
 	github.com/ipfs/go-verifcid v0.0.1
 	github.com/ipfs/interface-go-ipfs-core v0.4.0
-	github.com/ipld/go-car v0.2.1-0.20210312021557-7afab98d034f
+	github.com/ipld/go-car v0.3.1
 	github.com/ipld/go-codec-dagpb v1.2.1-0.20210405170603-d0b86f7623c2 // indirect
 	github.com/ipld/go-ipld-prime v0.9.1-0.20210324083106-dc342a9917db
 	github.com/jbenet/go-is-domain v1.0.5

go.sum

@@ -443,14 +443,14 @@ github.com/ipfs/go-ipld-format v0.0.1/go.mod h1:kyJtbkDALmFHv3QR6et67i35QzO3S0dC
 github.com/ipfs/go-ipld-format v0.0.2/go.mod h1:4B6+FM2u9OJ9zCV+kSbgFAZlOrv1Hqbf0INGQgiKf9k=
 github.com/ipfs/go-ipld-format v0.2.0 h1:xGlJKkArkmBvowr+GMCX0FEZtkro71K1AwiKnL37mwA=
 github.com/ipfs/go-ipld-format v0.2.0/go.mod h1:3l3C1uKoadTPbeNfrDi+xMInYKlx2Cvg1BuydPSdzQs=
-github.com/ipfs/go-ipld-legacy v0.0.0-20210325015318-9799f2cffab0 h1:PXjRvJkxqQ2EbwviF5GEURYqvhS/ulee/ZdVsVgVtHM=
-github.com/ipfs/go-ipld-legacy v0.0.0-20210325015318-9799f2cffab0/go.mod h1:86f5P/srAmh9GcIcWQR9lfFLZPrIyyXQeVlOWeeWEuI=
 github.com/ipfs/go-ipld-git v0.0.4-0.20210324174925-515bc5cab461 h1:bb97BkhX2Mc9EbwwYLK/rDXoofhkSjpALO//rlxgUw8=
 github.com/ipfs/go-ipld-git v0.0.4-0.20210324174925-515bc5cab461/go.mod h1:jtK6vhzvHtNm2YhKRxKMR8IQJAoZRtYoWqf8RnDeaIA=
 github.com/ipfs/go-ipld-git v0.0.4-0.20210326054912-6be33ddcbecc h1:57luC/Oc36sZBp4BAJ74MJGsAULBeQ5NLLRpTL6YJwI=
 github.com/ipfs/go-ipld-git v0.0.4-0.20210326054912-6be33ddcbecc/go.mod h1:jtK6vhzvHtNm2YhKRxKMR8IQJAoZRtYoWqf8RnDeaIA=
 github.com/ipfs/go-ipld-legacy v0.0.0-20210312014519-2895f54096d5 h1:5RLoebNIGmHmlcdTSdVrXGRF5sLy/wTiCUgWMeJvIII=
 github.com/ipfs/go-ipld-legacy v0.0.0-20210312014519-2895f54096d5/go.mod h1:1wv+3vTMw6axVoAJFisWzJ7tewUnrcr6AxymcZrd83k=
+github.com/ipfs/go-ipld-legacy v0.0.0-20210325015318-9799f2cffab0 h1:PXjRvJkxqQ2EbwviF5GEURYqvhS/ulee/ZdVsVgVtHM=
+github.com/ipfs/go-ipld-legacy v0.0.0-20210325015318-9799f2cffab0/go.mod h1:86f5P/srAmh9GcIcWQR9lfFLZPrIyyXQeVlOWeeWEuI=
 github.com/ipfs/go-ipns v0.0.2 h1:oq4ErrV4hNQ2Eim257RTYRgfOSV/s8BDaf9iIl4NwFs=
 github.com/ipfs/go-ipns v0.0.2/go.mod h1:WChil4e0/m9cIINWLxZe1Jtf77oz5L05rO2ei/uKJ5U=
 github.com/ipfs/go-log v0.0.1/go.mod h1:kL1d2/hzSpI0thNYjiKfjanbVNU+IIGA/WnNESY9leM=
@@ -498,6 +498,8 @@ github.com/ipfs/interface-go-ipfs-core v0.4.0 h1:+mUiamyHIwedqP8ZgbCIwpy40oX7QcX
 github.com/ipfs/interface-go-ipfs-core v0.4.0/go.mod h1:UJBcU6iNennuI05amq3FQ7g0JHUkibHFAfhfUIy927o=
 github.com/ipld/go-car v0.2.1-0.20210312021557-7afab98d034f h1:417+6v+keLsNoVi2vPJamDsW/ewuAs2uE3hlFt5muGs=
 github.com/ipld/go-car v0.2.1-0.20210312021557-7afab98d034f/go.mod h1:kHunAcD305JwLqwI9MfKvuQu4ljwWRZQWfDWPrkkhcg=
+github.com/ipld/go-car v0.3.1 h1:WT+3cdmXlvmWOlGxk9webhj4auGO5QvgqC2vCCkFRXs=
+github.com/ipld/go-car v0.3.1/go.mod h1:dPkEWeAK8KaVvH5TahaCs6Mncpd4lDMpkbs0/SPzuVs=
 github.com/ipld/go-codec-dagpb v1.0.2-0.20210308154810-d05d02fa186e/go.mod h1:oYexiw3WkBIVD5UTNkVuOd0iyEcLxqytAQa90F3nH9M=
 github.com/ipld/go-codec-dagpb v1.2.0/go.mod h1:6nBN7X7h8EOsEejZGqC7tej5drsdBAXbMHyBT+Fne5s=
 github.com/ipld/go-codec-dagpb v1.2.1-0.20210405170603-d0b86f7623c2 h1:m/ZZEoOdswHrrcikTC+fX4x6tnevJs0hoyNzijlT41A=