Merge pull request #269 from ropensci/fix-empty-refs

Handles NULL edges in oa_snowball

R/oa_snowball.R

@@ -114,6 +114,11 @@ oa_snowball <- function(identifier = NULL,
 
   # relationships/edges
   edges <- rbind(citing_rel, cited_rel)
+  if (is.null(edges)) {
+    message("No citations and no references for ", identifier)
+    edges <- tibble::tibble(from = character(0), to = character(0))
+    return(list(nodes = nodes, edges = edges))
+  }
   # remove duplicates when two input identifiers cite each other
   edges <- edges[!duplicated(edges), ]
   # remove edges to/from NA nodes

tests/testthat/test-oa_snowball.R

@@ -31,7 +31,7 @@ test_that("oa_snowball works for recent articles with no citations yet", {
 
   Sys.sleep(1/10)
   snowball_docs <- oa_snowball(
-    identifier = c("W4295757800", "W4296128995", "W4297497355")
+    identifier = c("W2033458484")
   )
   expect_true(is.list(snowball_docs))
 })