Add missing test cases for has_many

lib/dataloader/ecto.ex

@@ -872,6 +872,21 @@ if Code.ensure_loaded?(Ecto) do
         build_preload_lateral_query(rest, query, :join_last)
       end
 
+      defp build_preload_lateral_query(
+             [%Ecto.Association.Has{} = assoc | rest],
+             query,
+             :join_first
+           ) do
+        query =
+          query
+          |> join(:inner, [x], y in ^assoc.owner,
+            on: field(x, ^assoc.related_key) == field(y, ^assoc.owner_key)
+          )
+          |> Ecto.Association.combine_joins_query(assoc.where, 0)
+
+        build_preload_lateral_query(rest, query, :join_last)
+      end
+
       defp build_preload_lateral_query([assoc | rest], query, :join_first) do
         query =
           query
@@ -882,6 +897,23 @@ if Code.ensure_loaded?(Ecto) do
         build_preload_lateral_query(rest, query, :join_last)
       end
 
+      defp build_preload_lateral_query(
+             [%Ecto.Association.Has{} = assoc | rest],
+             query,
+             :join_last
+           ) do
+        binds_count = Ecto.Query.Builder.count_binds(query)
+
+        join_query =
+          query
+          |> Ecto.Association.combine_joins_query(assoc.where, binds_count - 1)
+          |> join(:inner, [..., x], y in ^assoc.owner,
+            on: field(x, ^assoc.related_key) == field(y, ^assoc.owner_key)
+          )
+
+        build_preload_lateral_query(rest, join_query, :join_last)
+      end
+
       defp build_preload_lateral_query([assoc | rest], query, :join_last) do
         query =
           query

test/dataloader/ecto/has_many_where_test.exs

@@ -1,7 +1,7 @@
 defmodule Dataloader.Ecto.HasManyWhereTest do
   use ExUnit.Case, async: true
 
-  alias Dataloader.{User, Post, Like}
+  alias Dataloader.{User, Post, Like, Picture, UserPicture}
   import Ecto.Query
   alias Dataloader.TestRepo, as: Repo
 
@@ -47,7 +47,7 @@ defmodule Dataloader.Ecto.HasManyWhereTest do
       assert [post1] == Dataloader.get(loader, Test, args, user1)
     end
 
-    test "simple filtered has_many in has_many through in first position", %{loader: loader} do
+    test "filtered has_many in has_many through in first position", %{loader: loader} do
       user1 = %User{username: "Ben Wilson"} |> Repo.insert!()
 
       post1 = %Post{user_id: user1.id, title: "foo", status: "published"} |> Repo.insert!()
@@ -65,5 +65,51 @@ defmodule Dataloader.Ecto.HasManyWhereTest do
 
       assert [like1] == Dataloader.get(loader, Test, args, user1)
     end
+
+    test "filtered has_many in has_many through in second position", %{loader: loader} do
+      user1 = %User{username: "Ben Wilson"} |> Repo.insert!()
+
+      pic1 = %Picture{url: "https://example.com/1.jpg"} |> Repo.insert!()
+      pic2 = %Picture{url: "https://example.com/2.jpg"} |> Repo.insert!()
+
+      %UserPicture{user_id: user1.id, picture_id: pic1.id} |> Repo.insert!()
+      %UserPicture{user_id: user1.id, picture_id: pic2.id} |> Repo.insert!()
+
+      like1 = %Like{user_id: user1.id, picture_id: pic1.id, status: "published"} |> Repo.insert!()
+
+      _like2 =
+        %Like{user_id: user1.id, picture_id: pic2.id, status: "unpublished"} |> Repo.insert!()
+
+      args = {:published_picture_likes, %{limit: 10}}
+
+      loader =
+        loader
+        |> Dataloader.load(Test, args, user1)
+        |> Dataloader.run()
+
+      assert [like1] == Dataloader.get(loader, Test, args, user1)
+    end
+
+    test "filtered has_many in has_many through in sandwich position", %{loader: loader} do
+      leaderboard = %Dataloader.Leaderboard{name: "Top Bloggers"} |> Repo.insert!()
+      user1 = %User{username: "Ben Wilson", leaderboard_id: leaderboard.id} |> Repo.insert!()
+
+      post1 = %Post{user_id: user1.id, title: "foo", status: "published"} |> Repo.insert!()
+      post2 = %Post{user_id: user1.id, title: "bar", status: "unpublished"} |> Repo.insert!()
+
+      like1 = %Like{user_id: user1.id, post_id: post1.id} |> Repo.insert!()
+
+      _like2 =
+        %Like{user_id: user1.id, post_id: post2.id, status: "unpublished"} |> Repo.insert!()
+
+      args = {:user_published_posts_likes, %{limit: 10}}
+
+      loader =
+        loader
+        |> Dataloader.load(Test, args, leaderboard)
+        |> Dataloader.run()
+
+      assert [like1] == Dataloader.get(loader, Test, args, leaderboard)
+    end
   end
 end

test/support/leaderboard.ex

@@ -9,5 +9,6 @@ defmodule Dataloader.Leaderboard do
     has_many(:user_pictures_published, through: [:users, :pictures_published])
     has_many(:user_pictures_likes, through: [:users, :pictures, :likes])
     has_many(:user_pictures_published_likes, through: [:users, :pictures_published, :likes])
+    has_many(:user_published_posts_likes, through: [:users, :published_posts, :likes])
   end
 end

test/support/picture.ex

@@ -5,5 +5,6 @@ defmodule Dataloader.Picture do
     field(:status, :string)
     field(:url, :string, null: false)
     has_many(:likes, Dataloader.Like)
+    has_many(:published_likes, Dataloader.Like, where: [status: "published"])
   end
 end

test/support/user.ex

@@ -36,6 +36,8 @@ defmodule Dataloader.User do
 
     many_to_many(:pictures, Dataloader.Picture, join_through: Dataloader.UserPicture)
 
+    has_many(:published_picture_likes, through: [:pictures, :published_likes])
+
     many_to_many(:pictures_published, Dataloader.Picture,
       join_through: Dataloader.UserPicture,
       join_where: [status: "published"],