Fix join count conflicts (#4592)

Author: greg-rychlewski

lib/ecto/query/builder/join.ex

@@ -165,11 +165,9 @@ defmodule Ecto.Query.Builder.Join do
       if is_nil(count_bind) do
         query =
           quote do
-            query = Ecto.Queryable.to_query(unquote(query))
-            join_count = Builder.count_binds(query)
-            query
+            Ecto.Queryable.to_query(unquote(query))
           end
-        {quote(do: join_count), query}
+        {quote(do: Builder.count_binds(unquote(query))), query}
       else
         {count_bind, query}
       end

test/ecto/query/builder/join_test.exs

@@ -202,4 +202,17 @@ defmodule Ecto.Query.Builder.JoinTest do
       end, [], __ENV__)
     end
   end
+
+  test "join count is incremented correctly for runtime sources" do
+    users_table = "users"
+    source_query = fn -> from p in "posts", join: c in "comments", on: true end
+
+    q =
+      from s in source_query.(),
+        join: j in subquery(from u in users_table, join: p in "profiles", on: true, select: u.id),
+        on: true,
+        select: {s.id, j.id}
+
+    assert {:{}, _, [_, {{:., [], [{:&, [], [2]}, :id]}, [], []}]} = q.select.expr
+  end
 end