Generate id for schemas without primary key

handles a case when embedded schema struct belongs to a regular record

lib/dataloader/ecto.ex

@@ -512,7 +512,15 @@ if Code.ensure_loaded?(Ecto) do
       defp get_keys({assoc_field, opts}, %schema{} = record) when is_atom(assoc_field) do
         validate_queryable(schema)
         primary_keys = schema.__schema__(:primary_key)
-        id = Enum.map(primary_keys, &Map.get(record, &1))
+
+        id =
+          if primary_keys == [] do
+            record
+            |> :erlang.term_to_iovec()
+            |> :erlang.md5()
+          else
+            Enum.map(primary_keys, &Map.get(record, &1))
+          end
 
         queryable = chase_down_queryable([assoc_field], schema)
 

mix.exs

@@ -67,7 +67,8 @@ defmodule Dataloader.Mixfile do
       {:ecto_sql, "~> 3.0", optional: true, only: :test},
       {:postgrex, "~> 0.14", only: :test, runtime: false},
       {:dialyxir, "~> 1.3.0", only: [:dev, :test], runtime: false},
-      {:ex_doc, "~> 0.24", only: :dev, runtime: false}
+      {:ex_doc, "~> 0.24", only: :dev, runtime: false},
+      {:jason, "~> 1.0", only: :test}
     ]
   end
 

mix.lock

@@ -8,6 +8,7 @@
   "ecto_sql": {:hex, :ecto_sql, "3.10.1", "6ea6b3036a0b0ca94c2a02613fd9f742614b5cfe494c41af2e6571bb034dd94c", [:mix], [{:db_connection, "~> 2.4.1 or ~> 2.5", [hex: :db_connection, repo: "hexpm", optional: false]}, {:ecto, "~> 3.10.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:myxql, "~> 0.6.0", [hex: :myxql, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.16.0 or ~> 0.17.0 or ~> 1.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:tds, "~> 2.1.1 or ~> 2.2", [hex: :tds, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.0 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "f6a25bdbbd695f12c8171eaff0851fa4c8e72eec1e98c7364402dda9ce11c56b"},
   "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
   "ex_doc": {:hex, :ex_doc, "0.29.4", "6257ecbb20c7396b1fe5accd55b7b0d23f44b6aa18017b415cb4c2b91d997729", [:mix], [{:earmark_parser, "~> 1.4.31", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "2c6699a737ae46cb61e4ed012af931b57b699643b24dabe2400a8168414bc4f5"},
+  "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
   "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},
   "makeup_erlang": {:hex, :makeup_erlang, "0.1.2", "ad87296a092a46e03b7e9b0be7631ddcf64c790fa68a9ef5323b6cbb36affc72", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "f3f5a1ca93ce6e092d92b6d9c049bcda58a3b617a8d888f8e7231c85630e8108"},

priv/test_repo/migrations/1_migrate_all.exs

@@ -1,4 +1,4 @@
-defmodule Absinthe.Ecto.TestRepo.Migrations.MigrateAll do
+defmodule Dataloader.Ecto.TestRepo.Migrations.MigrateAll do
   use Ecto.Migration
 
   def change do

test/dataloader/ecto/belongs_to_test.exs

@@ -1,7 +1,7 @@
 defmodule Dataloader.Ecto.BelongsToTest do
   use ExUnit.Case, async: true
 
-  alias Dataloader.{User, Post, Like}
+  alias Dataloader.{User, Post, Like, Country, Address}
   import Ecto.Query
   alias Dataloader.TestRepo, as: Repo
 
@@ -30,6 +30,11 @@ defmodule Dataloader.Ecto.BelongsToTest do
     |> limit(^limit)
   end
 
+  defp query(queryable, _args, test_pid) do
+    send(test_pid, :querying)
+    queryable
+  end
+
   describe "where in belongs_to association" do
     test "returns entity when where clause matches", %{loader: loader} do
       user1 = %User{username: "Ben Wilson"} |> Repo.insert!()
@@ -65,4 +70,26 @@ defmodule Dataloader.Ecto.BelongsToTest do
       assert nil == Dataloader.get(loader, Test, args, like1)
     end
   end
+
+  test "belongs_to is inside the embedded schema", %{loader: loader} do
+    country1 = %Country{name: "USA"} |> Repo.insert!()
+    country2 = %Country{name: "Canada"} |> Repo.insert!()
+
+    address1 = %Address{city: "New York", country_id: country1.id}
+    address2 = %Address{city: "Toronto", country_id: country2.id}
+    address3 = %Address{city: "Washington"}
+
+    args = {:country, %{}}
+
+    loader =
+      loader
+      |> Dataloader.load(Test, args, address1)
+      |> Dataloader.load(Test, args, address2)
+      |> Dataloader.load(Test, args, address3)
+      |> Dataloader.run()
+
+    assert country1 == Dataloader.get(loader, Test, args, address1)
+    assert country2 == Dataloader.get(loader, Test, args, address2)
+    assert nil == Dataloader.get(loader, Test, args, address3)
+  end
 end

test/support/address.ex

@@ -0,0 +1,9 @@
+defmodule Dataloader.Address do
+  use Ecto.Schema
+
+  @primary_key false
+  embedded_schema do
+    field(:city, :string)
+    belongs_to(:country, Dataloader.Country)
+  end
+end

test/support/country.ex

@@ -0,0 +1,7 @@
+defmodule Dataloader.Country do
+  use Ecto.Schema
+
+  schema "countries" do
+    field(:name, :string)
+  end
+end