Hotfix/absolute distinct fix (mojotech#80)

* Add failing test for distinct: true with join

* Subquery for counts of distinct: true queries. Fixes mojotech#79

* Be more explicit about checking for truthy distinct value

* Fix formatting

lib/scrivener/paginater/ecto/query.ex

@@ -53,7 +53,7 @@ defimpl Scrivener.Paginater, for: Ecto.Query do
     total_entries || 0
   end
 
-  defp aggregate(%{distinct: %{expr: [_ | _]}} = query) do
+  defp aggregate(%{distinct: %{expr: expr}} = query) when expr == true or is_list(expr) do
     query
     |> exclude(:select)
     |> count()

test/scrivener/paginator/ecto/query_test.exs

@@ -403,5 +403,21 @@ defmodule Scrivener.Paginator.Ecto.QueryTest do
       assert page.total_entries == 7
       assert page.total_pages == 2
     end
+
+    test "pagination plays nice with absolute distinct on a join query" do
+      create_posts()
+
+      page =
+        Post
+        |> distinct(true)
+        |> join(:inner, [p], c in assoc(p, :comments))
+        |> Scrivener.Ecto.Repo.paginate()
+
+      assert length(page.entries) == 1
+      assert page.page_size == 5
+      assert page.page_number == 1
+      assert page.total_entries == 1
+      assert page.total_pages == 1
+    end
   end
 end