Merge pull request #1021 from gjaldon/do-not-override-meta

Ensure __meta__ is not overridden in build/3

lib/ecto/model.ex

@@ -109,7 +109,7 @@ defmodule Ecto.Model do
   """
   def build(%{__struct__: model} = struct, assoc, attributes \\ %{}) do
     assoc = Ecto.Association.association_from_model!(model, assoc)
-    assoc.__struct__.build(assoc, struct, attributes)
+    assoc.__struct__.build(assoc, struct, Dict.delete(attributes, :__meta__))
   end
 
   @doc """

test/ecto/association_test.exs

@@ -355,6 +355,11 @@ defmodule Ecto.AssociationTest do
 
     # Overriding defaults
     assert build(%Summary{id: 1}, :post, title: "Hello").title == "Hello"
+
+    # Should not allow overriding of __meta__
+    meta = %{__meta__: %{source: {nil, "posts"}}}
+    comment = build(%Post{id: 1}, :comments, meta)
+    assert comment.__meta__.source == {nil, "comments"}
   end
 
   test "assoc/2" do