Return WriteConcernError from bulk writes

GODRIVER-975

Change-Id: Ie363b168fd7e60debd629c4f37040b90318554bd

Author: Divjot Arora

mongo/collection_internal_test.go

@@ -2090,3 +2090,38 @@ func TestCollection_FindOneAndUpdate_WriteConcernError(t *testing.T) {
 		t.Errorf("incorrect error type returned: %T", writeErr)
 	}
 }
+
+func TestCollection_BulkWrite(t *testing.T) {
+	t.Run("TestWriteConcernError", func(t *testing.T) {
+		if os.Getenv("TOPOLOGY") != "replica_set" {
+			t.Skip()
+		}
+
+		filter := bson.D{{"foo", "bar"}}
+		update := bson.D{{"$set", bson.D{{"foo", 10}}}}
+
+		testCases := []struct {
+			name   string
+			models []WriteModel
+		}{
+			{"insert", []WriteModel{NewInsertOneModel().SetDocument(bson.D{{"foo", 1}})}},
+			{"update", []WriteModel{NewUpdateOneModel().SetFilter(filter).SetUpdate(update)}},
+			{"delete", []WriteModel{NewDeleteOneModel().SetFilter(filter)}},
+		}
+
+		coll := createTestCollection(t, nil, nil, options.Collection().SetWriteConcern(impossibleWriteConcern))
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				_, err := coll.BulkWrite(ctx, tc.models)
+				require.Error(t, err)
+
+				bwException, ok := err.(BulkWriteException)
+				require.True(t, ok)
+
+				require.Equal(t, 0, len(bwException.WriteErrors),
+					"expected no write errors, got %v", bwException.WriteErrors)
+				require.NotNil(t, bwException.WriteConcernError)
+			})
+		}
+	})
+}

x/mongo/driver/bulk_write.go

@@ -164,6 +164,7 @@ func runBatch(
 
 		batchRes.InsertedCount = int64(res.N)
 		writeErrors = res.WriteErrors
+		batchErr.WriteConcernError = res.WriteConcernError
 	case DeleteOneModel, DeleteManyModel:
 		res, err := runDelete(ctx, ns, topo, selector, ss, sess, clock, wc, retryWrite, batch, continueOnError, registry)
 		if err != nil {
@@ -172,6 +173,7 @@ func runBatch(
 
 		batchRes.DeletedCount = int64(res.N)
 		writeErrors = res.WriteErrors
+		batchErr.WriteConcernError = res.WriteConcernError
 	case ReplaceOneModel, UpdateOneModel, UpdateManyModel:
 		res, err := runUpdate(ctx, ns, topo, selector, ss, sess, clock, wc, retryWrite, batch, bypassDocValidation,
 			continueOnError, registry)
@@ -183,6 +185,7 @@ func runBatch(
 		batchRes.ModifiedCount = res.ModifiedCount
 		batchRes.UpsertedCount = int64(len(res.Upserted))
 		writeErrors = res.WriteErrors
+		batchErr.WriteConcernError = res.WriteConcernError
 		for _, upsert := range res.Upserted {
 			batchRes.UpsertedIDs[upsert.Index] = upsert.ID
 		}