Make sure JWT VCs and VPs marshal into the correct format

vc/vc.go

@@ -37,9 +37,9 @@ func VCContextV1URI() ssi.URI {
 const (
 	// JSONLDCredentialProofFormat is the format for JSON-LD based credentials.
 	JSONLDCredentialProofFormat string = "ldp_vc"
-	// JWTCredentialsProofFormat is the format for JWT based credentials.
+	// JWTCredentialProofFormat is the format for JWT based credentials.
 	// Note: various specs have not yet decided on the exact const (jwt_vc or jwt_vc_json, etc), so this is subject to change.
-	JWTCredentialsProofFormat = "jwt_vc"
+	JWTCredentialProofFormat = "jwt_vc"
 )
 
 var errCredentialSubjectWithoutID = errors.New("credential subjects have no ID")
@@ -99,7 +99,7 @@ func parseJWTCredential(raw string) (*VerifiableCredential, error) {
 	} else if jti != nil {
 		result.ID = jti
 	}
-	result.format = JWTCredentialsProofFormat
+	result.format = JWTCredentialProofFormat
 	result.raw = raw
 	result.token = token
 	return &result, nil
@@ -190,6 +190,16 @@ func (vc VerifiableCredential) Proofs() ([]Proof, error) {
 }
 
 func (vc VerifiableCredential) MarshalJSON() ([]byte, error) {
+	if vc.raw != "" {
+		// Credential instance created through ParseVerifiableCredential()
+		if vc.format == JWTCredentialProofFormat {
+			// Marshal as JSON string
+			return json.Marshal(vc.raw)
+		}
+		// JSON-LD, already in JSON format so return as-is
+		return []byte(vc.raw), nil
+	}
+	// Must be a (new) JSON-LD credential (library does not support creating JWT VCs)
 	type alias VerifiableCredential
 	tmp := alias(vc)
 	if data, err := json.Marshal(tmp); err != nil {

vc/vc_test.go

@@ -27,7 +27,9 @@ BND3LDTn9H7FQokEsUEi8jKwXhGvoN3JtRa51xrNDgXDb0cq1UTYB-rK4Ft9YVmR1NI_ZOF8oGc_7wAp
 txJy6M1-lD7a5HTzanYTWBPAUHDZGyGKXdJw-W_x0IWChBzI8t3kpG253fg6V3tPgHeKXE94fz_QpYfg
 --7kLsyBAfQGbg`
 
-func TestVerifiableCredential_UnmarshalJSON(t *testing.T) {
+// TestVerifiableCredential_JSONMarshalling tests JSON marshalling of VerifiableCredential.
+// Credentials in JSON-LD format are marshalled JSON object, while JWT credentials are marshalled as JSON string.
+func TestVerifiableCredential_JSONMarshalling(t *testing.T) {
 	t.Run("JSON-LD", func(t *testing.T) {
 		input := VerifiableCredential{}
 		raw := `{
@@ -43,6 +45,10 @@ func TestVerifiableCredential_UnmarshalJSON(t *testing.T) {
 		assert.Equal(t, JSONLDCredentialProofFormat, input.Format())
 		assert.Equal(t, raw, input.Raw())
 		assert.Nil(t, input.JWT())
+		// Should marshal into JSON object
+		marshalled, err := json.Marshal(input)
+		require.NoError(t, err)
+		assert.True(t, strings.HasPrefix(string(marshalled), "{"))
 	})
 	t.Run("JWT", func(t *testing.T) {
 		input := VerifiableCredential{}
@@ -52,9 +58,13 @@ func TestVerifiableCredential_UnmarshalJSON(t *testing.T) {
 		assert.Equal(t, []ssi.URI{ssi.MustParseURI("VerifiableCredential"), ssi.MustParseURI("UniversityDegreeCredential")}, input.Type)
 		assert.Len(t, input.CredentialSubject, 1)
 		assert.NotNil(t, input.CredentialSubject[0].(map[string]interface{})["degree"])
-		assert.Equal(t, JWTCredentialsProofFormat, input.Format())
+		assert.Equal(t, JWTCredentialProofFormat, input.Format())
 		assert.Equal(t, raw, input.Raw())
 		assert.NotNil(t, input.JWT())
+		// Should marshal into JSON string
+		marshalled, err := json.Marshal(input)
+		require.NoError(t, err)
+		assert.JSONEq(t, `"`+raw+`"`, string(marshalled))
 	})
 }
 

vc/vp.go

@@ -155,19 +155,21 @@ func (vp VerifiablePresentation) Proofs() ([]Proof, error) {
 }
 
 func (vp VerifiablePresentation) MarshalJSON() ([]byte, error) {
-	switch vp.format {
-	case JWTPresentationProofFormat:
-		return json.Marshal(vp.raw)
-	case JSONLDPresentationProofFormat:
-		fallthrough
-	default:
-		type alias VerifiablePresentation
-		tmp := alias(vp)
-		if data, err := json.Marshal(tmp); err != nil {
-			return nil, err
-		} else {
-			return marshal.NormalizeDocument(data, pluralContext, marshal.Unplural(typeKey), marshal.Unplural(verifiableCredentialKey), marshal.Unplural(proofKey))
+	if vp.raw != "" {
+		// Presentation instance created through ParseVerifiablePresentation()
+		if vp.format == JWTPresentationProofFormat {
+			// Marshal as JSON string
+			return json.Marshal(vp.raw)
 		}
+		// JSON-LD, already in JSON format so return as-is
+		return []byte(vp.raw), nil
+	}
+	type alias VerifiablePresentation
+	tmp := alias(vp)
+	if data, err := json.Marshal(tmp); err != nil {
+		return nil, err
+	} else {
+		return marshal.NormalizeDocument(data, pluralContext, marshal.Unplural(typeKey), marshal.Unplural(verifiableCredentialKey), marshal.Unplural(proofKey))
 	}
 }
 

vc/vp_test.go

@@ -219,7 +219,7 @@ func TestParseVerifiablePresentation(t *testing.T) {
 		// Assert contained JWT VerifiableCredential was unmarshalled
 		assert.Len(t, vp.VerifiableCredential, 1)
 		vc := vp.VerifiableCredential[0]
-		assert.Equal(t, JWTCredentialsProofFormat, vc.Format())
+		assert.Equal(t, JWTCredentialProofFormat, vc.Format())
 		assert.Equal(t, "http://example.edu/credentials/3732", vc.ID.String())
 	})
 	t.Run("json.UnmarshalJSON for JWT-VP wrapped inside other document", func(t *testing.T) {