feat: append context if missing (trustbloc#1741)

pkg/doc/vc/vcutil/vcutil.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/samber/lo"
 	"github.com/trustbloc/vc-go/verifiable"
 
 	vcsverifiable "github.com/trustbloc/vcs/pkg/doc/verifiable"
@@ -102,19 +103,29 @@ func CreateIssuer(issuerDID, issuerName string) *verifiable.Issuer {
 }
 
 // AppendSignatureTypeContext appends context for JSONWebSignature2020 and BbsBlsSignature2020.
-func AppendSignatureTypeContext(context []string, signatureType vcsverifiable.SignatureType,
+func AppendSignatureTypeContext(
+	context []string,
+	signatureType vcsverifiable.SignatureType,
 ) []string {
 	if signatureType == vcsverifiable.JSONWebSignature2020 {
-		return append(context, jsonWebSignature2020Context)
+		return appendIfMissing(context, jsonWebSignature2020Context)
 	}
 
 	if signatureType == vcsverifiable.BbsBlsSignature2020 {
-		return append(context, bbsBlsSignature2020Context)
+		return appendIfMissing(context, bbsBlsSignature2020Context)
 	}
 
 	return context
 }
 
+func appendIfMissing(contexts []string, context string) []string {
+	if lo.Contains(contexts, context) {
+		return contexts
+	}
+
+	return append(contexts, context)
+}
+
 // PrependCredentialPrefix prepends prefix to credential.ID.
 func PrependCredentialPrefix(credential *verifiable.Credential, prefix string) *verifiable.Credential {
 	contents := credential.Contents()

pkg/doc/vc/vcutil/vcutil_test.go

@@ -10,6 +10,7 @@ import (
 	"encoding/json"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"github.com/trustbloc/vc-go/verifiable"
 
@@ -206,3 +207,24 @@ func TestPrependCredentialPrefix(t *testing.T) {
 
 	require.Equal(t, "prefix_did:example:ebfeb1f712ebc6f1c276e12ec21", credential.Contents().ID)
 }
+
+func TestAppendIfMissing(t *testing.T) {
+	t.Run("missing", func(t *testing.T) {
+		assert.EqualValues(t, []string{
+			"abcd",
+			"https://w3c-ccg.github.io/lds-jws2020/contexts/lds-jws2020-v1.json",
+		}, AppendSignatureTypeContext([]string{
+			"abcd",
+		}, vcsverifiable.JSONWebSignature2020))
+	})
+
+	t.Run("already exists", func(t *testing.T) {
+		assert.EqualValues(t, []string{
+			"abcd",
+			"https://w3c-ccg.github.io/lds-jws2020/contexts/lds-jws2020-v1.json",
+		}, AppendSignatureTypeContext([]string{
+			"abcd",
+			"https://w3c-ccg.github.io/lds-jws2020/contexts/lds-jws2020-v1.json",
+		}, vcsverifiable.JSONWebSignature2020))
+	})
+}