Properly handle empty collections in cypherToList

Fixes #40.

R/cypherToList.R

@@ -60,7 +60,7 @@ cypherToList.graph = function(graph, query, ...) {
     for(j in 1:length(result$columns)) {
       name = result$columns[[j]]
       record = data[[i]][[j]]
-      if(!is.null(names(record)) || !is.list(record)) {
+      if(!is.null(names(record)) || !is.list(record) || length(record) == 0) {
         datum[[name]] = configure_result(record)
       } else {
         depth = length(record)

tests/testthat/test-cypherToList.R

@@ -137,4 +137,33 @@ test_that("it can return nodes with empty collections as properties", {
   n = n[[1]]$n
 
   expect_equal(length(n$a), 0)
+})
+
+test_that("it can return empty collections", {
+  clear(neo4j, input=F)
+
+  query = "RETURN [] AS col"
+  response = cypherToList(neo4j, query)[[1]]
+
+  expect_equal(response$col, list())
+})
+
+test_that("it can return empty collections along with a value", {
+  clear(neo4j, input=F)
+
+  query = "RETURN [] AS col, 5 AS five"
+  response = cypherToList(neo4j, query)[[1]]
+
+  expect_equal(response$col, list())
+  expect_equal(response$five, 5)
+})
+
+test_that("it can return empty collections and non-empty collections", {
+  clear(neo4j, input=F)
+
+  query = "RETURN [] AS col1, [5,6] AS col2"
+  response = cypherToList(neo4j, query)[[1]]
+
+  expect_equal(response$col1, list())
+  expect_equal(response$col2, list(5,6))
 })