Fix mapper enumerable count (#16)

Author: jonatanklosko

lib/table/mapper.ex

@@ -25,7 +25,9 @@ defmodule Table.Mapper do
 
   defimpl Enumerable do
     def count(mapper) do
-      Enumerable.count(mapper.enumerable)
+      with {:error, _} <- Enumerable.count(mapper.enumerable) do
+        {:error, __MODULE__}
+      end
     end
 
     # The mapping is not necessarily reversible, so we fall

test/mapper_test.exs

@@ -6,6 +6,9 @@ defmodule Table.MapperTest do
   test "count" do
     enumerable = 1..3 |> Mapper.map(fn x -> x * x end)
     assert Enum.count(enumerable) == 3
+
+    enumerable = [1, 2, 3] |> Mapper.map(fn x -> x * x end)
+    assert Enum.count(enumerable) == 3
   end
 
   test "reduce" do

test/zipper_test.exs

@@ -6,6 +6,9 @@ defmodule Table.ZipperTest do
   test "count" do
     enumerable = Zipper.zip([1..4, 1..3, 1..5])
     assert Enum.count(enumerable) == 3
+
+    enumerable = Zipper.zip([1..4, [1, 2, 3], 1..5])
+    assert Enum.count(enumerable) == 3
   end
 
   test "reduce" do