diff options
| -rw-r--r-- | lib/elixir/lib/stream.ex | 6 | ||||
| -rw-r--r-- | lib/elixir/test/elixir/stream_test.exs | 8 |
2 files changed, 14 insertions, 0 deletions
diff --git a/lib/elixir/lib/stream.ex b/lib/elixir/lib/stream.ex index ae7f22cc2..e797c0239 100644 --- a/lib/elixir/lib/stream.ex +++ b/lib/elixir/lib/stream.ex @@ -1155,6 +1155,10 @@ defmodule Stream do @spec cycle(Enumerable.t) :: Enumerable.t def cycle(enumerable) + def cycle([]) do + raise ArgumentError, "cannot cycle over empty enumerable" + end + def cycle(enumerable) when is_list(enumerable) do unfold {enumerable, enumerable}, fn {source, [h | t]} -> {h, {source, t}} @@ -1185,6 +1189,8 @@ defmodule Stream do {:stream_cycle, acc} -> {:halted, acc} else + {state, []} when state in [:done, :halted] -> + raise ArgumentError, "cannot cycle over empty enumerable" {state, acc} when state in [:done, :halted] -> do_cycle(cycle, cycle, {:cont, acc}) {:suspended, acc, continuation} -> diff --git a/lib/elixir/test/elixir/stream_test.exs b/lib/elixir/test/elixir/stream_test.exs index 69d7f9efc..4dd905e30 100644 --- a/lib/elixir/test/elixir/stream_test.exs +++ b/lib/elixir/test/elixir/stream_test.exs @@ -168,6 +168,14 @@ defmodule StreamTest do stream = Stream.cycle([1, 2, 3]) assert is_function(stream) + assert_raise ArgumentError, "cannot cycle over empty enumerable", fn -> + Stream.cycle([]) + end + + assert_raise ArgumentError, "cannot cycle over empty enumerable", fn -> + Stream.cycle(%{}) |> Enum.to_list() + end + assert Stream.cycle([1, 2, 3]) |> Stream.take(5) |> Enum.to_list == [1, 2, 3, 1, 2] assert Enum.take(stream, 5) == [1, 2, 3, 1, 2] end |