test: Add a test for an expression calculation using an aggregation in a sort

This replicates an issue seen.

We have an expression calculation using a aggregation from a transitive
relationship.  If that calculation is used in a sort, the text of the
expression is passed as the aggregate name, instead of a varaible name
such as "aggregate0" etc.

Author: rellen

test/calculation_test.exs

@@ -1076,4 +1076,62 @@ defmodule AshPostgres.CalculationTest do
     highest_score = hd(Enum.sort(scores, :desc))
     assert post_with_highest_score.score == highest_score
   end
+
+  test "an expression calculation can use an aggregate" do
+    post1 =
+      Post
+      |> Ash.Changeset.for_create(:create, %{title: "my post"})
+      |> Ash.create!()
+
+    _post2 =
+      Post
+      |> Ash.Changeset.for_create(:create, %{title: "another post"})
+      |> Ash.create!()
+
+    author =
+      Author
+      |> Ash.Changeset.for_create(:create, %{
+        first_name: "ashley"
+      })
+      |> Ash.create!()
+
+    Comment
+    |> Ash.Changeset.for_create(:create, %{title: "first comment"})
+    |> Ash.Changeset.manage_relationship(:post, post1, type: :append_and_remove)
+    |> Ash.create!()
+
+    first_comment_by_author =
+      Comment
+      |> Ash.Changeset.for_create(:create, %{title: "first comment by Ashley"})
+      |> Ash.Changeset.manage_relationship(:author, author, type: :append_and_remove)
+      |> Ash.Changeset.manage_relationship(:post, post1, type: :append_and_remove)
+      |> Ash.create!()
+
+    Comment
+    |> Ash.Changeset.for_create(:create, %{title: "another comment"})
+    |> Ash.Changeset.manage_relationship(:post, post1, type: :append_and_remove)
+    |> Ash.create!()
+
+    second_comment_by_author =
+      Comment
+      |> Ash.Changeset.for_create(:create, %{title: "first comment by Ashley"})
+      |> Ash.Changeset.manage_relationship(:author, author, type: :append_and_remove)
+      |> Ash.Changeset.manage_relationship(:post, post1, type: :append_and_remove)
+      |> Ash.create!()
+
+    post1 =
+      Post
+      |> Ash.Query.for_read(:read_by_comment_author, %{
+        author_id: author.id
+      })
+      |> Ash.Query.sort_input([
+        {"datetime_of_first_comment_by_author", {%{author_id: author.id}, :desc}}
+      ])
+      |> Ash.read_one!()
+
+    assert DateTime.compare(
+             post1.datetime_of_first_comment_by_author,
+             first_comment_by_author.created_at
+           )
+  end
 end

test/support/resources/post.ex

@@ -488,6 +488,20 @@ defmodule AshPostgres.Test.Post do
       pagination(keyset?: true, default_limit: 25)
       filter(expr(count_nils(latest_comment.linked_comment_post_ids) == 0))
     end
+
+    read :read_by_comment_author do
+      argument(:author_id, :uuid, allow_nil?: false)
+
+      filter(expr(comments.author_id == ^arg(:author_id)))
+
+      prepare(
+        build(
+          load: [
+            datetime_of_first_comment_by_author: %{author_id: arg(:author_id)}
+          ]
+        )
+      )
+    end
   end
 
   identities do
@@ -1030,6 +1044,20 @@ defmodule AshPostgres.Test.Post do
     calculate(:latest_comment_title, :string, expr(latest_comment.title), allow_nil?: true)
 
     calculate(:concated_comment_titles, :string, expr(fragment("concat(?)", comment_titles)))
+
+    calculate :datetime_of_first_comment_by_author,
+              :utc_datetime_usec,
+              expr(
+                first(comments,
+                  field: :created_at,
+                  query: [
+                    filter: author_id == ^arg(:author_id)
+                  ]
+                )
+              ) do
+      public?(true)
+      argument(:author_id, :uuid, allow_nil?: false)
+    end
   end
 
   aggregates do