Simplify custom Marshal, remove Unmarshal

Signed-off-by: Cody Soyland <codysoyland@github.com>

pkg/verify/signed_entity.go

@@ -223,45 +223,26 @@ func NewVerificationResult() *VerificationResult {
 	}
 }
 
-// verificationResultRawStatement is a helper struct to marshal/unmarshal
-// It is used because in_toto.Statement is a protobuf message and we want to
-// store it as a raw message so we can use protojson to marshal/unmarshal it
-//
-// See https://github.com/in-toto/attestation/issues/363
-type verificationResultRawStatement struct {
-	MediaType          string                        `json:"mediaType"`
-	Statement          json.RawMessage               `json:"statement,omitempty"`
-	Signature          *SignatureVerificationResult  `json:"signature,omitempty"`
-	VerifiedTimestamps []TimestampVerificationResult `json:"verifiedTimestamps"`
-	VerifiedIdentity   *CertificateIdentity          `json:"verifiedIdentity,omitempty"`
-}
-
+// MarshalJSON deals with protojson needed for the Statement.
+// Can be removed when https://github.com/in-toto/attestation/pull/403 is merged.
+// TODO: Should we also add UnmarshalJSON?
 func (b *VerificationResult) MarshalJSON() ([]byte, error) {
 	statement, err := protojson.Marshal(b.Statement)
 	if err != nil {
 		return nil, err
 	}
-	return json.Marshal(&verificationResultRawStatement{
-		MediaType:          b.MediaType,
-		Statement:          statement,
-		Signature:          b.Signature,
-		VerifiedTimestamps: b.VerifiedTimestamps,
-		VerifiedIdentity:   b.VerifiedIdentity,
+	// creating a type alias to avoid infinite recursion, as MarshalJSON is
+	// not copied into the alias.
+	type Alias VerificationResult
+	return json.Marshal(struct {
+		Alias
+		Statement json.RawMessage `json:"statement,omitempty"`
+	}{
+		Alias:     Alias(*b),
+		Statement: statement,
 	})
 }
 
-func (b *VerificationResult) UnmarshalJSON(data []byte) error {
-	var aux verificationResultRawStatement
-	if err := json.Unmarshal(data, &aux); err != nil {
-		return err
-	}
-	b.MediaType = aux.MediaType
-	b.Signature = aux.Signature
-	b.VerifiedTimestamps = aux.VerifiedTimestamps
-	b.VerifiedIdentity = aux.VerifiedIdentity
-	return protojson.Unmarshal(aux.Statement, b.Statement)
-}
-
 type PolicyOption func(*PolicyConfig) error
 type ArtifactPolicyOption func(*PolicyConfig) error