improvement: support parent in sort expressions

lib/data_layer.ex

@@ -552,12 +552,22 @@ defmodule AshPostgres.DataLayer do
       |> default_bindings(resource, context)
 
     case context[:data_layer][:lateral_join_source] do
-      {_, [{%{resource: resource}, _, _, _} | _]} ->
+      {_, [{%{resource: resource}, _, _, _} | rest]} ->
         parent =
           resource
           |> resource_to_query(nil)
           |> default_bindings(resource, context)
 
+        parent =
+          case rest do
+            [{resource, _, _, %{name: join_relationship_name}} | _] ->
+              binding_data = %{type: :inner, path: [join_relationship_name], source: resource}
+              add_binding(parent, binding_data)
+
+            _ ->
+              parent
+          end
+
         ash_bindings =
           data_layer_query.__ash_bindings__
           |> Map.put(:parent_bindings, Map.put(parent.__ash_bindings__, :parent?, true))

lib/expr.ex

@@ -1055,14 +1055,15 @@ defmodule AshPostgres.Expr do
          type
        ) do
     parent? = Map.get(bindings.parent_bindings, :parent_is_parent_as?, true)
+    new_bindings = Map.put(bindings.parent_bindings, :parent?, parent?)
 
     do_dynamic_expr(
       %{
         query
-        | __ash_bindings__: Map.put(bindings.parent_bindings, :parent?, parent?)
+        | __ash_bindings__: new_bindings
       },
       expr,
-      bindings,
+      new_bindings,
       embedded?,
       type
     )
@@ -1607,7 +1608,8 @@ defmodule AshPostgres.Expr do
     end
   end
 
-  defp set_parent_path(query, parent) do
+  @doc false
+  def set_parent_path(query, parent) do
     # This is a stupid name. Its actually the path we *remove* when stepping up a level. I.e the child's path
     Map.update!(query, :__ash_bindings__, fn ash_bindings ->
       ash_bindings

lib/sort.ex

@@ -20,6 +20,7 @@ defmodule AshPostgres.Sort do
                  %{
                    resource: resource,
                    aggregates: %{},
+                   parent_stack: query.__ash_bindings__[:parent_resources] || [],
                    calculations: %{},
                    public?: false
                  }
@@ -84,14 +85,30 @@ defmodule AshPostgres.Sort do
             |> Ash.Filter.hydrate_refs(%{
               resource: resource,
               aggregates: query.__ash_bindings__.aggregate_defs,
+              parent_stack: query.__ash_bindings__[:parent_resources] || [],
               calculations: %{},
               public?: false
             })
             |> Ash.Filter.move_to_relationship_path(relationship_path)
             |> case do
               {:ok, expr} ->
+                bindings =
+                  if query.__ash_bindings__[:parent_bindings] do
+                    Map.update!(query.__ash_bindings__, :parent_bindings, fn parent ->
+                      Map.put(parent, :parent_is_parent_as?, false)
+                    end)
+                  else
+                    query.__ash_bindings__
+                  end
+
                 expr =
-                  AshPostgres.Expr.dynamic_expr(query, expr, query.__ash_bindings__, false, type)
+                  AshPostgres.Expr.dynamic_expr(
+                    query,
+                    expr,
+                    bindings,
+                    false,
+                    type
+                  )
 
                 {:cont, {:ok, query_expr ++ [{order, expr}]}}
 

test/sort_test.exs

@@ -4,6 +4,8 @@ defmodule AshPostgres.SortTest do
   alias AshPostgres.Test.{Api, Comment, Post, PostLink}
 
   require Ash.Query
+  require Ash.Sort
+  import Ash.Expr
 
   test "multi-column sorts work" do
     Post
@@ -181,4 +183,46 @@ defmodule AshPostgres.SortTest do
     |> Ash.Query.sort(:c_times_p)
     |> Api.read!()
   end
+
+  test "calculations can sort on expressions" do
+    post1 =
+      Post
+      |> Ash.Changeset.new(%{title: "aaa", score: 0})
+      |> Api.create!()
+
+    post2 =
+      Post
+      |> Ash.Changeset.new(%{title: "bbb", score: 1})
+      |> Api.create!()
+
+    post3 =
+      Post
+      |> Ash.Changeset.new(%{title: "ccc", score: 0})
+      |> Api.create!()
+
+    PostLink
+    |> Ash.Changeset.new()
+    |> Ash.Changeset.manage_relationship(:source_post, post1, type: :append)
+    |> Ash.Changeset.manage_relationship(:destination_post, post3, type: :append)
+    |> Api.create!()
+
+    PostLink
+    |> Ash.Changeset.new()
+    |> Ash.Changeset.manage_relationship(:source_post, post2, type: :append)
+    |> Ash.Changeset.manage_relationship(:destination_post, post2, type: :append)
+    |> Api.create!()
+
+    PostLink
+    |> Ash.Changeset.new()
+    |> Ash.Changeset.manage_relationship(:source_post, post3, type: :append)
+    |> Ash.Changeset.manage_relationship(:destination_post, post1, type: :append)
+    |> Api.create!()
+
+    posts_query =
+      Ash.Query.sort(Post, Ash.Sort.expr_sort(source(post_links.state)))
+
+    Post
+    |> Ash.Query.load(linked_posts: posts_query)
+    |> Api.read!()
+  end
 end