improvement: add has filter predicate

lib/ash/filter/filter.ex

@@ -22,6 +22,7 @@ defmodule Ash.Filter do
     Eq,
     GreaterThan,
     GreaterThanOrEqual,
+    Has,
     In,
     LessThan,
     LessThanOrEqual,
@@ -45,7 +46,8 @@ defmodule Ash.Filter do
                LessThan,
                GreaterThan,
                LessThanOrEqual,
-               GreaterThanOrEqual
+               GreaterThanOrEqual,
+               Has
              ] ++ Ash.Query.Operator.Basic.operator_modules()
 
   @builtins @functions ++ @operators

lib/ash/query/operator/has.ex

@@ -0,0 +1,17 @@
+defmodule Ash.Query.Operator.Has do
+  @moduledoc """
+  left has 1
+
+  this predicate matches if the right is in the list on the left
+
+  This actually just reverses the inputs and uses `in`.
+  """
+  use Ash.Query.Operator,
+    operator: :has,
+    predicate?: true,
+    types: [[{:array, :any}, :same]]
+
+  def new(left, right) do
+    Ash.Query.Operator.In.new(right, left)
+  end
+end

lib/ash/query/operator/operator.ex

@@ -211,7 +211,8 @@ defmodule Ash.Query.Operator do
       Ash.Query.Operator.IsNil,
       Ash.Query.Operator.LessThanOrEqual,
       Ash.Query.Operator.LessThan,
-      Ash.Query.Operator.NotEq
+      Ash.Query.Operator.NotEq,
+      Ash.Query.Operator.Has
     ] ++ Ash.Query.Operator.Basic.operator_modules()
   end
 

lib/ash/query/query.ex

@@ -481,6 +481,13 @@ defmodule Ash.Query do
     soft_escape(%Ash.Query.Call{name: op, args: args, operator?: true}, escape?)
   end
 
+  defp do_expr({left, _, [{op, _, [right]}]}, escape?)
+       when is_atom(op) and op in @operator_symbols and is_atom(left) do
+    args = Enum.map([{left, [], nil}, right], &do_expr(&1, false))
+
+    soft_escape(%Ash.Query.Call{name: op, args: args, operator?: true}, escape?)
+  end
+
   defp do_expr({op, _, args}, escape?) when is_atom(op) and is_list(args) do
     args = Enum.map(args, &do_expr(&1, false))