handle NotLoaded structs when manipulating lists of not persisted data

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 ## Unreleased
 
+## [0.1.2] - 2021-08-29
+
+### Fixed
+
+- Handle `Ecto.Association.NotLoaded` structs when appending, prepending or
+  inserting data into relations that are child relations of newly added, not
+  persisted data.
+
 ## [0.1.1] - 2021-08-28
 
 ### Changed

README.md

@@ -11,7 +11,7 @@ Add `ecto_nested_changeset` to your list of dependencies in `mix.exs`:
 ```elixir
 def deps do
   [
-    {:ecto_nested_changeset, "~> 0.1.1"}
+    {:ecto_nested_changeset, "~> 0.1.2"}
   ]
 end
 ```

example/lib/nested_web/live/owner_live/form_component.ex

@@ -17,8 +17,6 @@ defmodule NestedWeb.OwnerLive.FormComponent do
 
   @impl true
   def handle_event("validate", %{"owner" => owner_params}, socket) do
-    owner_params = prepare_params(owner_params)
-
     changeset =
       socket.assigns.owner
       |> Members.change_owner(owner_params)
@@ -110,18 +108,6 @@ defmodule NestedWeb.OwnerLive.FormComponent do
     end
   end
 
-  # puts empty lists into association fields if no associations were added
-  defp prepare_params(owner_params) do
-    owner_params
-    |> Map.put_new("pets", [])
-    |> Map.update!(
-      "pets",
-      &Enum.into(&1, %{}, fn {key, pet} ->
-        {key, Map.put_new(pet, "toys", [])}
-      end)
-    )
-  end
-
   defp deleted?(form) do
     input_value(form, :delete) in ["true", true]
   end

lib/ecto_nested_changeset.ex

@@ -8,6 +8,7 @@ defmodule EctoNestedChangeset do
 
   import Ecto.Changeset
 
+  alias Ecto.Association.NotLoaded
   alias Ecto.Changeset
 
   @doc """
@@ -215,11 +216,13 @@ defmodule EctoNestedChangeset do
 
   defp nested_update(:append, %Changeset{} = changeset, [field], value)
        when is_atom(field) do
-    Changeset.put_change(
-      changeset,
-      field,
-      get_change_or_field(changeset, field) ++ [value]
-    )
+    new_value =
+      case {get_change_or_field(changeset, field), changeset.action} do
+        {%NotLoaded{}, :insert} -> [value]
+        {previous_value, _} -> previous_value ++ [value]
+      end
+
+    Changeset.put_change(changeset, field, new_value)
   end
 
   defp nested_update(:append, %{} = data, [field], value) when is_atom(field) do
@@ -230,11 +233,13 @@ defmodule EctoNestedChangeset do
 
   defp nested_update(:prepend, %Changeset{} = changeset, [field], value)
        when is_atom(field) do
-    Changeset.put_change(
-      changeset,
-      field,
-      [value | get_change_or_field(changeset, field)]
-    )
+    new_value =
+      case {get_change_or_field(changeset, field), changeset.action} do
+        {%NotLoaded{}, :insert} -> [value]
+        {previous_value, _} -> [value | previous_value]
+      end
+
+    Changeset.put_change(changeset, field, new_value)
   end
 
   defp nested_update(:prepend, %{} = data, [field], value)
@@ -249,6 +254,17 @@ defmodule EctoNestedChangeset do
     List.insert_at(items, index, value)
   end
 
+  defp nested_update(:insert, %Changeset{} = changeset, [field, index], value)
+       when is_atom(field) and is_integer(index) do
+    new_value =
+      case {get_change_or_field(changeset, field), changeset.action} do
+        {%NotLoaded{}, :insert} -> [value]
+        {previous_value, _} -> List.insert_at(previous_value, index, value)
+      end
+
+    Changeset.put_change(changeset, field, new_value)
+  end
+
   defp nested_update(:update, %Changeset{} = changeset, [field], func)
        when is_atom(field) do
     value = get_change_or_field(changeset, field)

mix.exs

@@ -1,7 +1,7 @@
 defmodule EctoNestedChangeset.MixProject do
   use Mix.Project
 
-  @version "0.1.1"
+  @version "0.1.2"
   @source_url "https://github.com/woylie/ecto_nested_changeset"
 
   def project do

test/ecto_nested_changeset_test.exs

@@ -53,6 +53,31 @@ defmodule EctoNestedChangesetTest do
              } = changeset.changes
     end
 
+    test "appends item at a sub field of a new list item" do
+      changeset =
+        %Category{id: 1, posts: []}
+        |> change()
+        |> append_at(:posts, %Post{title: "first"})
+        |> append_at([:posts, 0, :comments], %Comment{})
+
+      assert %{
+               posts: [
+                 %Ecto.Changeset{
+                   action: :insert,
+                   changes: %{
+                     comments: [
+                       %Ecto.Changeset{
+                         action: :insert,
+                         data: %Comment{}
+                       }
+                     ]
+                   },
+                   data: %Post{title: "first"}
+                 }
+               ]
+             } = changeset.changes
+    end
+
     test "appends item at a root level field with existing data" do
       changeset =
         %Category{id: 1, posts: [%Post{id: 1, title: "existing"}]}
@@ -164,6 +189,31 @@ defmodule EctoNestedChangesetTest do
              } = changeset.changes
     end
 
+    test "prepends item at a sub field of a new list item" do
+      changeset =
+        %Category{id: 1, posts: []}
+        |> change()
+        |> prepend_at(:posts, %Post{title: "first"})
+        |> prepend_at([:posts, 0, :comments], %Comment{})
+
+      assert %{
+               posts: [
+                 %Ecto.Changeset{
+                   action: :insert,
+                   changes: %{
+                     comments: [
+                       %Ecto.Changeset{
+                         action: :insert,
+                         data: %Comment{}
+                       }
+                     ]
+                   },
+                   data: %Post{title: "first"}
+                 }
+               ]
+             } = changeset.changes
+    end
+
     test "prepend item at a root level field with existing data" do
       changeset =
         %Category{id: 1, posts: [%Post{id: 1, title: "existing"}]}
@@ -283,6 +333,31 @@ defmodule EctoNestedChangesetTest do
              } = changeset.changes
     end
 
+    test "inserts item at a sub field of a new list item" do
+      changeset =
+        %Category{id: 1, posts: []}
+        |> change()
+        |> insert_at([:posts, 0], %Post{title: "first"})
+        |> insert_at([:posts, 0, :comments, 0], %Comment{})
+
+      assert %{
+               posts: [
+                 %Ecto.Changeset{
+                   action: :insert,
+                   changes: %{
+                     comments: [
+                       %Ecto.Changeset{
+                         action: :insert,
+                         data: %Comment{}
+                       }
+                     ]
+                   },
+                   data: %Post{title: "first"}
+                 }
+               ]
+             } = changeset.changes
+    end
+
     test "inserts item at a root level field with existing data" do
       changeset =
         %Category{