From e0114f4c02cb27d781db54796eeb6475a707379a Mon Sep 17 00:00:00 2001
From: hadley <h.wickham@gmail.com>
Date: Thu, 9 Jun 2016 07:18:48 -0500
Subject: [PATCH] Allow spread to work with list cols

Fixes #199
---
 NEWS.md                      | 2 ++
 R/id.R                       | 5 +++++
 tests/testthat/test-spread.R | 8 ++++++++
 3 files changed, 15 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index dbb482c28..0d6ebb055 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -31,6 +31,8 @@
   as "key<sep>value". Additionally, if sep is `NULL` missing values will be
   converted to `<NA>` (#68).
 
+* `spread()` works in the presence of list-columns (#199)
+
 * `unnest()` works with non-syntactic names (#190).
 
 * `unnest()` gains a `sep` argument. If non-null, this will rename the 
diff --git a/R/id.R b/R/id.R
index 02ec83d7f..f28f77d4c 100644
--- a/R/id.R
+++ b/R/id.R
@@ -47,6 +47,11 @@ id_var <- function(x, drop = FALSE) {
   } else if (length(x) == 0) {
     id <- integer()
     n <- 0L
+  } else if (is.list(x)) {
+    # Sorting lists isn't supported
+    levels <- unique(x)
+    id <- match(x, levels)
+    n <- max(id)
   } else {
     levels <- sort(unique(x), na.last = TRUE)
     id <- match(x, levels)
diff --git a/tests/testthat/test-spread.R b/tests/testthat/test-spread.R
index 84b4ed291..64b3af333 100644
--- a/tests/testthat/test-spread.R
+++ b/tests/testthat/test-spread.R
@@ -145,6 +145,14 @@ test_that("complex values are preserved  (#134)", {
   expect_equal(out2$b, 3:4 + 1i)
 })
 
+test_that("can spread with nested columns", {
+  df <- tibble::data_frame(x = c("a", "a"), y = 1:2, z = list(1:2, 3:5))
+  out <- spread(df, x, y)
+
+  expect_equal(out$a, 1:2)
+  expect_equal(out$z, df$z)
+})
+
 test_that("spread gives one column when no existing non-spread vars", {
   df <- data_frame(
     key = c("a", "b", "c"),