fix(merkledag): address PR comments

Author: hannahhoward

coding_test.go

@@ -30,7 +30,6 @@ func init() {
 		panic(err)
 	}
 	benchInput = enc
-	// println(len(benchInput))
 }
 
 func BenchmarkRoundtrip(b *testing.B) {
@@ -46,7 +45,6 @@ func BenchmarkRoundtrip(b *testing.B) {
 			if err != nil {
 				b.Fatal(err)
 			}
-			// println(len(benchInput), len(enc))
 			_ = enc
 		}
 	})

node.go

@@ -17,6 +17,7 @@ import (
 // Common errors
 var (
 	ErrNotProtobuf  = fmt.Errorf("expected protobuf dag node")
+	ErrNotRawNode   = fmt.Errorf("expected raw bytes node")
 	ErrLinkNotFound = fmt.Errorf("no link by that name")
 )
 
@@ -27,6 +28,18 @@ type immutableProtoNode struct {
 
 // ProtoNode represents a node in the IPFS Merkle DAG.
 // nodes have opaque data and a set of navigable links.
+// ProtoNode is a go-ipld-legacy.UniversalNode, meaning it is both
+// a go-ipld-prime node and a go-ipld-format node.
+// ProtoNode maintains compatibility with it's original implementation
+// as a go-ipld-format only node, which included some mutability, namely the
+// the ability to add/remove links in place
+//
+// TODO: We should be able to eventually replace this implementation with
+// * go-codec-dagpb for basic DagPB encode/decode to go-ipld-prime
+// * go-unixfsnode ADLs for higher level DAGPB functionality
+// For the time being however, go-unixfsnode is read only and
+// this mutable protonode implementation is needed to support go-unixfs,
+// the only library that implements both read and write for UnixFS v1.
 type ProtoNode struct {
 	links []*format.Link
 	data  []byte

prime.go

@@ -1,10 +1,18 @@
 package merkledag
 
 import (
-	"github.com/ipld/go-ipld-prime"
 	dagpb "github.com/ipld/go-codec-dagpb"
+	"github.com/ipld/go-ipld-prime"
 )
 
+// Protonode was originally implemented as a go-ipld-format node, and included
+// functionality that does not fit well into the model for go-ipld-prime, namely
+// the ability ot modify the node in place.
+
+// In order to support the go-ipld-prime interface, all of these prime methods
+// serialize and rebuild the go-ipld-prime node as needed, so that it remains up
+// to date with mutations made via the add/remove link methods
+
 // Kind returns a value from the Kind enum describing what the
 // essential serializable kind of this node is (map, list, integer, etc).
 // Most other handling of a node requires first switching upon the kind.

raw.go

@@ -114,7 +114,7 @@ func (rn *RawNode) MarshalJSON() ([]byte, error) {
 
 func RawNodeConverter(b blocks.Block, nd ipld.Node) (legacy.UniversalNode, error) {
 	if nd.Kind() != ipld.Kind_Bytes {
-		return nil, ErrNotProtobuf
+		return nil, ErrNotRawNode
 	}
 	return &RawNode{b, nd}, nil
 }