review

.github/workflows/ci.yml

@@ -5,7 +5,7 @@ on: push
 env:
   MIX_ENV: test
   OTP_VERSION_SPEC: "24.2.1"
-  ELIXIR_VERSION_SPEC: "1.14"
+  ELIXIR_VERSION_SPEC: "1.13.3"
 
 jobs:
   compile:

.tool-versions

@@ -1,2 +1,2 @@
-elixir 1.14.2-otp-25
-erlang 25.1.2
+elixir 1.13.3-otp-24
+erlang 24.2.1

lib/ecto_diff.ex

@@ -367,33 +367,45 @@ defmodule EctoDiff do
     end
   end
 
-  defp diff_association(previous, current, %{cardinality: :many, through: [through, field]}, acc, opts) do
+  defp diff_association(
+         previous,
+         current,
+         %{cardinality: :many, through: [through, assoc_field], owner: owner},
+         acc,
+         opts
+       ) do
     assoc_diff =
       acc
       |> Keyword.get_values(through)
       |> List.flatten()
-      |> Enum.map(& &1[:changes][field])
+      |> Enum.map(& &1[:changes][assoc_field])
 
     diff =
       case assoc_diff do
         [_ | _] = diff ->
           List.flatten(diff)
 
         _ ->
-          {previous, current} =
-            case length(previous) - length(current) do
-              0 -> {previous, current}
-              n when n > 0 -> {previous, current ++ List.duplicate(nil, n)}
-              n when n < 0 -> {previous ++ List.duplicate(nil, -n), current}
-            end
-
-          Enum.zip_with([previous, current], fn [p, c] -> do_diff(p, c, opts) end)
+          through_association = owner.__schema__(:association, through).related
+          association = through_association.__schema__(:association, assoc_field)
+
+          diff_association(previous, current, association, acc, opts)
+          |> Keyword.get_values(assoc_field)
+          |> List.flatten()
       end
 
-    if no_changes?(diff), do: acc, else: [{field, diff} | acc]
+    if no_changes?(diff), do: acc, else: [{assoc_field, diff} | acc]
   end
 
-  defp diff_association(previous, current, %{cardinality: :many, field: field, related: struct}, acc, opts) do
+  defp diff_association(
+         previous,
+         current,
+         %{cardinality: :many, field: field} = association,
+         acc,
+         opts
+       ) do
+    %{related: struct} = association
+
     primary_key_fields = get_primary_key_fields(struct, opts)
 
     if primary_key_fields == [],
@@ -455,6 +467,7 @@ defmodule EctoDiff do
   end
 
   defp no_changes?([_ | _] = changes), do: Enum.any?(changes, &no_changes?/1)
+  defp no_changes?([]), do: true
   defp no_changes?(%{effect: effect, changes: map}) when map == %{} and effect in [:added, :changed], do: true
   defp no_changes?(_), do: false
 

mix.exs

@@ -8,7 +8,7 @@ defmodule EctoDiff.MixProject do
     [
       app: :ecto_diff,
       version: @version,
-      elixir: "~> 1.14",
+      elixir: "~> 1.7",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,
       deps: deps(),

test/ecto_diff_test.exs

@@ -733,13 +733,16 @@ defmodule EctoDiffTest do
         })
         |> Repo.update()
 
-      updated_pet = Repo.preload(updated_pet, [:resources, :toys])
+      updated_pet = Repo.preload(updated_pet, :toys)
 
       id = pet.id
       [%{id: resource_id}] = updated_pet.resources
-      [ball_id, mouse_id] = Enum.map(updated_pet.toys, & &1.id)
+      %{"ball" => ball_id, "mouse" => mouse_id} = Enum.into(updated_pet.toys, %{}, &{&1.name, &1.id})
 
       {:ok, diff} = EctoDiff.diff(pet, updated_pet)
+      [%{changes: %{toys: resource_toys}}] = diff.changes.resources
+
+      assert resource_toys == diff.changes.toys
 
       assert %EctoDiff{
                effect: :changed,
@@ -799,9 +802,9 @@ defmodule EctoDiffTest do
         |> Repo.insert()
 
       id = pet.id
-      pet = Repo.preload(pet, [:resources, :toys])
+      pet = Repo.preload(pet, :toys)
 
-      [ball_id, mouse_id] = Enum.map(pet.toys, & &1.id)
+      %{"ball" => ball_id, "mouse" => mouse_id} = Enum.into(pet.toys, %{}, &{&1.name, &1.id})
       [%{id: resource_id}] = pet.resources
 
       {:ok, updated_pet} =
@@ -855,7 +858,7 @@ defmodule EctoDiffTest do
         |> Pet.new()
         |> Repo.insert()
 
-      pet = Repo.preload(pet, [:resources, :toys])
+      pet = Repo.preload(pet, :toys)
       id = pet.id
       [%{id: resource_id}] = pet.resources
       [ball_id] = Enum.map(pet.toys, & &1.id)
@@ -902,7 +905,7 @@ defmodule EctoDiffTest do
         |> Pet.new()
         |> Repo.insert()
 
-      pet = Repo.preload(pet, [:resources, :toys])
+      pet = Repo.preload(pet, :toys)
       {:ok, updated_pet} = pet |> Pet.update(%{name: "McFluffFace"}) |> Repo.update()
       id = pet.id