Leave boolean predicates out of a value policy

lib/active_admin_filter_extensions/policies.rb

@@ -232,10 +232,29 @@ def with_groups
 
       # The filter's own predicate dropdown submits _gt/_lt/_not_eq and friends beside the
       # derived head key; a value policy guarding only the head leaves the same column one
-      # dropdown click from unpoliced. Siblings = request keys naming the same attribute.
+      # dropdown click from unpoliced. Siblings = request keys naming the same attribute,
+      # minus the predicates answered by a boolean rather than by a value of the attribute's
+      # own type: `?q[customer_id_null]=true` carries "true", which `sanitize: :digits`
+      # empties and `validate: :integer` refuses - the reset would then drop a condition a
+      # drill-down link spelled out. A boolean predicate the filter declares itself stays
+      # policed: that one its author asked for.
       def sibling_predicate_keys(q, keys)
         bases = keys.map { |key| strip_ransack_predicate(key) }
-        q.keys.select { |key| bases.include?(strip_ransack_predicate(key)) }
+        declared = keys.map(&:to_s)
+        q.keys.select do |key|
+          next false unless bases.include?(strip_ransack_predicate(key))
+
+          declared.include?(key.to_s) || !boolean_predicate?(key)
+        end
+      end
+
+      def boolean_predicate?(name)
+        # Without Ransack there is nothing to ask - and nothing is stripped either, so a
+        # sibling can only be the declared key itself.
+        return false unless defined?(::Ransack::Predicate)
+
+        predicate = ::Ransack::Predicate.detect_from_string(name.to_s)
+        predicate && ::Ransack::Predicate.named(predicate)&.type == :boolean
       end
 
       def strip_ransack_predicate(name)

lib/active_admin_filter_extensions/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module ActiveAdminFilterExtensions
-  VERSION = "1.0.0"
+  VERSION = "1.0.1"
 end

spec/integration/numeric_builtins_spec.rb

@@ -78,6 +78,19 @@ def query_of(url)
       expect(page).to have_no_content("drop me")
     end
 
+    it "leaves a boolean predicate of the same attribute to Ransack" do
+      # `?q[position_null]=true` is answered by "true", not by a value of the column's own
+      # type: the digits sanitizer would empty it and the integer validator refuse it, and the
+      # reset would drop a condition the admin's own drill-down link spelled out.
+      Post.create!(title: "no position", body: "no position body", status: "draft")
+
+      visit "/admin/integer_posts?q%5Bposition_null%5D=true"
+
+      expect(query_of(page.current_url)["q"]).to eq("position_null" => "true")
+      expect(page).to have_content("no position")
+      expect(page).to have_no_content("keep me")
+    end
+
     it "sanitizes a sibling predicate too" do
       visit "/admin/integer_posts?q%5Bposition_lt%5D=2%200a"