Return non-error results for TrustBundleList fetching when peering is disabled

agent/cache-types/trust_bundles.go

@@ -8,6 +8,8 @@ import (
 
 	"github.com/mitchellh/hashstructure"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	grpcstatus "google.golang.org/grpc/status"
 
 	"github.com/hashicorp/consul/agent/cache"
 	external "github.com/hashicorp/consul/agent/grpc-external"
@@ -87,11 +89,18 @@ func (t *TrustBundles) Fetch(_ cache.FetchOptions, req cache.Request) (cache.Fet
 	// Fetch
 	reply, err := t.Client.TrustBundleListByService(external.ContextWithToken(context.Background(), reqReal.Token), reqReal.Request)
 	if err != nil {
-		return result, err
+		grpcErr, ok := grpcstatus.FromError(err)
+		if !ok || grpcErr.Code() != codes.FailedPrecondition {
+			return result, err
+		}
+
+		// handle the FailedPrecondition error and synthesize a fake result
+		result.Value = &pbpeering.TrustBundleListByServiceResponse{}
+		result.Index = 1
+	} else {
+		result.Value = reply
+		result.Index = reply.Index
 	}
 
-	result.Value = reply
-	result.Index = reply.Index
-
 	return result, nil
 }

agent/cache-types/trust_bundles_test.go

@@ -7,6 +7,8 @@ import (
 
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/codes"
+	grpcstatus "google.golang.org/grpc/status"
 
 	"github.com/hashicorp/consul/agent/cache"
 	"github.com/hashicorp/consul/proto/pbpeering"
@@ -48,6 +50,29 @@ func TestTrustBundles(t *testing.T) {
 	}, result)
 }
 
+func TestTrustBundles_PeeringDisabled(t *testing.T) {
+	client := NewMockTrustBundleLister(t)
+	typ := &TrustBundles{Client: client}
+
+	var resp *pbpeering.TrustBundleListByServiceResponse
+
+	// Expect the proper call.
+	// This also returns the canned response above.
+	client.On("TrustBundleListByService", mock.Anything, mock.Anything).
+		Return(resp, grpcstatus.Error(codes.FailedPrecondition, "peering must be enabled to use this endpoint"))
+
+	// Fetch and assert against the result.
+	result, err := typ.Fetch(cache.FetchOptions{}, &TrustBundleListRequest{
+		Request: &pbpeering.TrustBundleListByServiceRequest{
+			ServiceName: "foo",
+		},
+	})
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.EqualValues(t, 1, result.Index)
+	require.NotNil(t, result.Value)
+}
+
 func TestTrustBundles_badReqType(t *testing.T) {
 	client := pbpeering.NewPeeringServiceClient(nil)
 	typ := &TrustBundles{Client: client}