fix(blob | nodebuilder/da): Revert custom marshaling for blob.Proof (#3204)

Reverts a change introduced in
#3146 that
unintentionally broke `blob.Proof` serialisation.

Resolves #3173

Author: renaynay

blob/blob.go

@@ -39,33 +39,6 @@ type Proof []*nmt.Proof
 
 func (p Proof) Len() int { return len(p) }
 
-func (p Proof) MarshalJSON() ([]byte, error) {
-	proofs := make([]string, 0, len(p))
-	for _, proof := range p {
-		proofBytes, err := proof.MarshalJSON()
-		if err != nil {
-			return nil, err
-		}
-		proofs = append(proofs, string(proofBytes))
-	}
-	return json.Marshal(proofs)
-}
-
-func (p *Proof) UnmarshalJSON(b []byte) error {
-	var proofs []string
-	if err := json.Unmarshal(b, &proofs); err != nil {
-		return err
-	}
-	for _, proof := range proofs {
-		var nmtProof nmt.Proof
-		if err := nmtProof.UnmarshalJSON([]byte(proof)); err != nil {
-			return err
-		}
-		*p = append(*p, &nmtProof)
-	}
-	return nil
-}
-
 // equal is a temporary method that compares two proofs.
 // should be removed in BlobService V1.
 func (p Proof) equal(input Proof) error {

nodebuilder/da/service.go

@@ -3,6 +3,7 @@ package da
 import (
 	"context"
 	"encoding/binary"
+	"encoding/json"
 	"fmt"
 	"strings"
 
@@ -83,7 +84,7 @@ func (s *Service) GetProofs(ctx context.Context, ids []da.ID, namespace da.Names
 		if err != nil {
 			return nil, err
 		}
-		proofs[i], err = proof.MarshalJSON()
+		proofs[i], err = json.Marshal(proof)
 		if err != nil {
 			return nil, err
 		}
@@ -153,7 +154,7 @@ func (s *Service) Validate(
 	proofs := make([]*blob.Proof, len(ids))
 	for i, daProof := range daProofs {
 		blobProof := &blob.Proof{}
-		err := blobProof.UnmarshalJSON(daProof)
+		err := json.Unmarshal(daProof, blobProof)
 		if err != nil {
 			return nil, err
 		}