From 704bf7ba0f735238583644da9daf2574407a2faf Mon Sep 17 00:00:00 2001
From: Ben Wilson <benwilson512@gmail.com>
Date: Mon, 27 Jan 2020 18:49:15 -0500
Subject: [PATCH 1/2] more flexible functions

---
 lib/fable/events.ex | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/lib/fable/events.ex b/lib/fable/events.ex
index 77c1071..9901620 100644
--- a/lib/fable/events.ex
+++ b/lib/fable/events.ex
@@ -239,18 +239,35 @@ defmodule Fable.Events do
           Keyword.t()
         ) ::
           transation_fun
-  def emit(config, %{__meta__: %Ecto.Schema.Metadata{}} = aggregate, fun, changes \\ %{}, opts)
-      when is_function(fun, 3) do
+  def emit(config, %{__meta__: %Ecto.Schema.Metadata{}} = aggregate, fun, changes \\ %{}, opts) do
     check_schema_fields(aggregate)
 
     fn ->
       aggregate = lock(aggregate, config.repo) || aggregate
-      events = fun.(aggregate, config.repo, changes)
-      result_of_applied_events = handle_events(config, aggregate, events, opts)
-      rollback_on_error(config.repo, result_of_applied_events)
+
+      case call_fun(fun, aggregate, config, changes) do
+        {:error, reason} ->
+          config.repo.rollback(reason)
+
+        events ->
+          result_of_applied_events = handle_events(config, aggregate, events, opts)
+          rollback_on_error(config.repo, result_of_applied_events)
+      end
     end
   end
 
+  defp call_fun(fun, aggregate, _config, _changes) when is_function(fun, 1) do
+    fun.(aggregate)
+  end
+
+  defp call_fun(fun, aggregate, config, _changes) when is_function(fun, 2) do
+    fun.(aggregate, config.repo)
+  end
+
+  defp call_fun(fun, aggregate, config, changes) when is_function(fun, 3) do
+    fun.(aggregate, config.repo, changes)
+  end
+
   @doc false
   @spec emit(
           Fable.Config.t(),
@@ -261,8 +278,7 @@ defmodule Fable.Events do
           Keyword.t()
         ) ::
           Ecto.Multi.t()
-  def emit(%{repo: repo} = config, %Ecto.Multi{} = multi, aggregate, name, fun, opts)
-      when is_function(fun, 3) do
+  def emit(%{repo: repo} = config, %Ecto.Multi{} = multi, aggregate, name, fun, opts) do
     Ecto.Multi.run(multi, name, fn ^repo, changes ->
       emit(config, aggregate, fun, changes, opts)
       |> repo.transaction()

From 05ff805221bafbc1ae662e2bdf59066d9e6f3123 Mon Sep 17 00:00:00 2001
From: Ben Wilson <benwilson512@gmail.com>
Date: Tue, 28 Jan 2020 09:52:43 -0500
Subject: [PATCH 2/2] require at least 2 arity function

---
 lib/fable/events.ex | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/lib/fable/events.ex b/lib/fable/events.ex
index 9901620..b73771f 100644
--- a/lib/fable/events.ex
+++ b/lib/fable/events.ex
@@ -256,10 +256,6 @@ defmodule Fable.Events do
     end
   end
 
-  defp call_fun(fun, aggregate, _config, _changes) when is_function(fun, 1) do
-    fun.(aggregate)
-  end
-
   defp call_fun(fun, aggregate, config, _changes) when is_function(fun, 2) do
     fun.(aggregate, config.repo)
   end