Improve Ecto.InvalidChangesetError message for embeds (#1796)

lib/ecto/exceptions.ex

@@ -81,22 +81,50 @@ defmodule Ecto.InvalidChangesetError do
   defexception [:action, :changeset]
 
   def message(%{action: action, changeset: changeset}) do
+    changes = extract_changes(changeset)
+    errors = Ecto.Changeset.traverse_errors(changeset, & &1)
+
     """
     could not perform #{action} because changeset is invalid.
 
-    * Changeset changes
+    Applied changes
+
+    #{pretty changes}
 
-    #{inspect changeset.changes}
+    Params
 
-    * Changeset params
+    #{pretty changeset.params}
 
-    #{inspect changeset.params}
+    Errors
 
-    * Changeset errors
+    #{pretty errors}
 
-    #{inspect changeset.errors}
+    Changeset
+
+    #{pretty changeset}
     """
   end
+
+  defp pretty(term) do
+    inspect(term, pretty: true)
+    |> String.split("\n")
+    |> Enum.map_join("\n", &"    " <> &1)
+  end
+
+  defp extract_changes(%Ecto.Changeset{changes: changes}) do
+    Enum.reduce(changes, %{}, fn({key, value}, acc) ->
+      case value do
+        %Ecto.Changeset{action: :delete} -> acc
+        _ -> Map.put(acc, key, extract_changes(value))
+      end
+    end)
+  end
+  defp extract_changes([%Ecto.Changeset{action: :delete} | tail]),
+    do: extract_changes(tail)
+  defp extract_changes([%Ecto.Changeset{} = changeset | tail]),
+    do: [extract_changes(changeset) | extract_changes(tail)]
+  defp extract_changes(other),
+    do: other
 end
 
 defmodule Ecto.CastError do

test/ecto/repo_test.exs

@@ -196,7 +196,7 @@ defmodule Ecto.RepoTest do
   end
 
   test "insert!, update!, insert_or_update! and delete! fail on invalid changeset" do
-    invalid = %Ecto.Changeset{valid?: false, data: %MySchema{}}
+    invalid = %Ecto.Changeset{valid?: false, data: %MySchema{}, types: %{}}
 
     assert_raise Ecto.InvalidChangesetError,
                  ~r"could not perform insert because changeset is invalid", fn ->