chore(balance, members): split members balance in two fields

apps/app/lib/app/balance.ex

@@ -209,7 +209,7 @@ defmodule App.Balance do
 
     Enum.map(members, fn
       # If a member's balance has already been corrupted, it cannot be computed correctly
-      %{balance: {:error, _}} = member ->
+      %{balance_errors: [_ | _]} = member ->
         member
 
       %{id: ^member_id} = member ->
@@ -252,30 +252,18 @@ defmodule App.Balance do
   end
 
   # add reasons to the balance error reason list, or initialize the list
-  defp add_balance_errors(member, new_reasons) do
-    reasons =
-      case member.balance do
-        {:error, old_reasons} -> Enum.uniq_by(new_reasons ++ old_reasons, & &1.uniq_hash)
-        _ -> new_reasons
-      end
+  defp add_balance_errors(member, new_errors) do
+    errors = Enum.uniq_by(member.balance_errors ++ new_errors, & &1.uniq_hash)
 
-    %{member | balance: {:error, reasons}}
+    %{member | balance_errors: errors}
   end
 
   @doc """
   Checks if the computed balance of the member has an error.
   """
   @spec has_balance_error?(BookMember.t()) :: boolean()
   def has_balance_error?(member) do
-    match?({:error, _reasons}, member.balance)
-  end
-
-  @spec member_balance_error_reasons(BookMember.t()) :: error_reasons() | nil
-  defp member_balance_error_reasons(member) do
-    case member.balance do
-      {:error, reasons} -> reasons
-      _ -> nil
-    end
+    member.balance_errors != []
   end
 
   @typedoc """
@@ -300,7 +288,10 @@ defmodule App.Balance do
   """
   @spec transactions([BookMember.t()]) :: {:ok, [transaction()]} | {:error, error_reasons()}
   def transactions(members) do
-    error_reasons = Enum.find_value(members, &member_balance_error_reasons/1)
+    error_reasons =
+      Enum.find_value(members, fn member ->
+        if has_balance_error?(member), do: member.balance_errors
+      end)
 
     if error_reasons do
       {:error, error_reasons}

apps/app/lib/app/books/book_member.ex

@@ -8,7 +8,6 @@ defmodule App.Books.BookMember do
   import Ecto.Query
 
   alias App.Accounts.User
-  alias App.Balance
   alias App.Balance.BalanceConfig
   alias App.Books.Book
 
@@ -26,7 +25,8 @@ defmodule App.Books.BookMember do
           email: String.t() | nil,
           balance_config_id: BalanceConfig.id() | nil,
           balance_config: BalanceConfig.t() | Ecto.Association.NotLoaded.t() | nil,
-          balance: Money.t() | {:error, Balance.error_reasons()} | nil,
+          balance: Money.t() | nil,
+          balance_errors: [String.t()],
           inserted_at: NaiveDateTime.t() | nil,
           updated_at: NaiveDateTime.t() | nil
         }
@@ -48,9 +48,10 @@ defmodule App.Books.BookMember do
 
     # the current balance configuration for this member
     belongs_to :balance_config, BalanceConfig
-    # Filled by the `Balance` context. Maybe be set to `{:error, reasons}` if the
-    # balance cannot be computed.
+    # Filled by the `Balance` context. If the `:balance_errors` is set,  the balance
+    # was not computed correctly.
     field :balance, Money.Ecto.Composite.Type, virtual: true
+    field :balance_errors, {:array, :string}, virtual: true, default: []
 
     timestamps()
   end

apps/app/test/app/balance_test.exs

@@ -298,23 +298,21 @@ defmodule App.BalanceTest do
       member1_id = member1.id
       expected_hash = "revenues_missing_#{member1_id}"
 
-      assert {:error,
-              [
-                %{
-                  kind: :revenues_missing,
-                  uniq_hash: ^expected_hash,
-                  extra: %{member: %{id: ^member1_id}}
-                }
-              ]} = member1.balance
-
-      assert {:error,
-              [
-                %{
-                  kind: :revenues_missing,
-                  uniq_hash: ^expected_hash,
-                  extra: %{member: %{id: ^member1_id}}
-                }
-              ]} = member2.balance
+      assert [
+               %{
+                 kind: :revenues_missing,
+                 uniq_hash: ^expected_hash,
+                 extra: %{member: %{id: ^member1_id}}
+               }
+             ] = member1.balance_errors
+
+      assert [
+               %{
+                 kind: :revenues_missing,
+                 uniq_hash: ^expected_hash,
+                 extra: %{member: %{id: ^member1_id}}
+               }
+             ] = member2.balance_errors
 
       assert Money.equal?(member3.balance, Money.new!(:EUR, -20))
     end
@@ -425,7 +423,12 @@ defmodule App.BalanceTest do
 
     test "returns :error when the balance of a member is corrupted", %{book: book} do
       member1 = book_member_fixture(book, balance: Money.new!(:EUR, 10))
-      member2 = book_member_fixture(book, balance: {:error, ["could not compute balance"]})
+
+      member2 =
+        book_member_fixture(book,
+          balance: Money.new!(:EUR, 10),
+          balance_errors: ["could not compute balance"]
+        )
 
       assert Balance.transactions([member1, member2]) == {:error, ["could not compute balance"]}
     end