retrieval: Drop the RootSelector hack

api/types.go

@@ -210,14 +210,9 @@ type RestrievalRes struct {
 type Selector string
 
 type DagSpec struct {
-	// RootSelector specifies root node
-	// - when using textselector, the path specifies the root node
-	// - if nil then RootSelector is inferred from DataSelector
-	// - must match a single node
-	RootSelector *Selector
-
 	// DataSelector matches data to be retrieved
 	// - when using textselector, the path specifies subtree
+	// - the matched graph must have a single root
 	DataSelector *Selector
 }
 
@@ -226,9 +221,8 @@ type ExportRef struct {
 
 	// DAGs array specifies a list of DAGs to export
 	// - If exporting into a car file, defines car roots
-	// - If exporting into unixfs files, only one DAG is supported, DataSelector is ignored
+	// - If exporting into unixfs files, only one DAG is supported, DataSelector is only used to find the root node
 	// - When not specified defaults to a single DAG:
-	//   - Root - the root node: `{".": {}}`
 	//   - Data - the entire DAG: `{"R":{"l":{"none":{}},":>":{"a":{">":{"@":{}}}}}}`
 	DAGs []DagSpec
 

cli/client_retr.go

@@ -451,39 +451,35 @@ var clientRetrieveLsCmd = &cli.Command{
 		ctx := ReqContext(cctx)
 		afmt := NewAppFmt(cctx.App)
 
-		rootSelector := lapi.Selector(`{".": {}}`)
-		dataSelector := lapi.Selector(fmt.Sprintf(`{"a":{">":{"R":{"l":{"depth":%d},":>":{"a":{">":{"|":[{"@":{}},{".":{}}]}}}}}}}`, cctx.Int("depth")))
+		dataSelector := lapi.Selector(fmt.Sprintf(`{"R":{"l":{"depth":%d},":>":{"a":{">":{"|":[{"@":{}},{".":{}}]}}}}}`, cctx.Int("depth")))
 
 		if cctx.IsSet("datamodel-path") {
-			rootSelector, err = pathToSel(cctx.String("datamodel-path"), nil)
-			if err != nil {
-				return err
-			}
-
 			ssb := builder.NewSelectorSpecBuilder(basicnode.Prototype.Any)
-			dataSelector, err = pathToSel(cctx.String("datamodel-path"), ssb.ExploreAll(
-				ssb.ExploreRecursive(selector.RecursionLimitDepth(int64(cctx.Int("depth"))), ssb.ExploreAll(ssb.ExploreUnion(ssb.Matcher(), ssb.ExploreRecursiveEdge()))),
-			))
+			dataSelector, err = pathToSel(cctx.String("datamodel-path"),
+				ssb.ExploreUnion(
+					ssb.Matcher(),
+					ssb.ExploreAll(
+						ssb.ExploreRecursive(selector.RecursionLimitDepth(int64(cctx.Int("depth"))), ssb.ExploreAll(ssb.ExploreUnion(ssb.Matcher(), ssb.ExploreRecursiveEdge()))),
+					)))
 			if err != nil {
-				return err
+				return xerrors.Errorf("parsing datamodel path: %w", err)
 			}
 		}
 
 		eref, err := retrieve(ctx, cctx, fapi, &dataSelector, afmt.Printf)
 		if err != nil {
-			return err
+			return xerrors.Errorf("retrieve: %w", err)
 		}
 
 		fmt.Println() // separate retrieval events from results
 
 		eref.DAGs = append(eref.DAGs, lapi.DagSpec{
-			RootSelector: &rootSelector,
 			DataSelector: &dataSelector,
 		})
 
 		rc, err := ClientExportStream(ainfo.Addr, ainfo.AuthHeader(), *eref, true)
 		if err != nil {
-			return err
+			return xerrors.Errorf("export: %w", err)
 		}
 		defer rc.Close() // nolint
 

node/impl/client/client.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -1024,26 +1025,26 @@ func parseDagSpec(ctx context.Context, root cid.Cid, dsp []api.DagSpec, ds forma
 
 	out := make([]dagSpec, len(dsp))
 	for i, spec := range dsp {
-		if spec.RootSelector == nil {
-			spec.RootSelector = spec.DataSelector
-		}
 
-		if spec.RootSelector != nil {
+		// if a selector is specified, find it's root node
+		if spec.DataSelector != nil {
 			var rsn ipld.Node
 
-			if strings.HasPrefix(string(*spec.RootSelector), "{") {
+			if strings.HasPrefix(string(*spec.DataSelector), "{") {
 				var err error
-				rsn, err = selectorparse.ParseJSONSelector(string(*spec.RootSelector))
+				rsn, err = selectorparse.ParseJSONSelector(string(*spec.DataSelector))
 				if err != nil {
-					return nil, xerrors.Errorf("failed to parse json-selector '%s': %w", *spec.RootSelector, err)
+					return nil, xerrors.Errorf("failed to parse json-selector '%s': %w", *spec.DataSelector, err)
 				}
 			} else {
-				selspec, _ := textselector.SelectorSpecFromPath(textselector.Expression(*spec.RootSelector), nil) //nolint:errcheck
+				selspec, _ := textselector.SelectorSpecFromPath(textselector.Expression(*spec.DataSelector), nil) //nolint:errcheck
 				rsn = selspec.Node()
 			}
 
 			var newRoot cid.Cid
 
+			var errHalt = errors.New("halt walk")
+
 			if err := utils.TraverseDag(
 				ctx,
 				ds,
@@ -1061,7 +1062,7 @@ func parseDagSpec(ctx context.Context, root cid.Cid, dsp []api.DagSpec, ds forma
 							// todo: is the n ipld.Node above the node we want as the (sub)root?
 							// todo: how to go from ipld.Node to a cid?
 							newRoot = root
-							return nil
+							return errHalt
 						}
 
 						cidLnk, castOK := p.LastBlock.Link.(cidlink.Link)
@@ -1070,10 +1071,12 @@ func parseDagSpec(ctx context.Context, root cid.Cid, dsp []api.DagSpec, ds forma
 						}
 
 						newRoot = cidLnk.Cid
+
+						return errHalt
 					}
 					return nil
 				},
-			); err != nil {
+			); err != nil && err != errHalt {
 				return nil, xerrors.Errorf("error while locating partial retrieval sub-root: %w", err)
 			}