Allow Utils.inspect and Utils.to_s with no arguments

lib/liquid/utils.rb

@@ -93,7 +93,12 @@ def self.to_liquid_value(obj)
       obj
     end
 
-    def self.to_s(obj, seen = {})
+    # Optional first argument so Module#to_s / #inspect keep working when
+    # tooling (for example SimpleCov) calls these with no arguments.
+    def self.to_s(obj = (no_object = true
+                         nil), seen = {})
+      return super() if no_object
+
       case obj
       when BigDecimal
         obj.to_s("F")
@@ -113,7 +118,10 @@ def self.to_s(obj, seen = {})
       end
     end
 
-    def self.inspect(obj, seen = {})
+    def self.inspect(obj = (no_object = true
+                            nil), seen = {})
+      return super() if no_object
+
       case obj
       when Hash
         # If the custom hash implementation overrides `#inspect`, use their

test/unit/utils_unit_test.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class UtilsUnitTest < Minitest::Test
+  def test_inspect_with_no_arguments_uses_module_inspect
+    assert_equal("Liquid::Utils", Liquid::Utils.inspect)
+  end
+
+  def test_to_s_with_no_arguments_uses_module_to_s
+    assert_equal("Liquid::Utils", Liquid::Utils.to_s)
+  end
+
+  def test_inspect_still_renders_objects
+    assert_equal("nil", Liquid::Utils.inspect(nil))
+    assert_equal("{\"a\"=>1}", Liquid::Utils.inspect({ "a" => 1 }))
+  end
+
+  def test_to_s_still_renders_objects
+    assert_equal("", Liquid::Utils.to_s(nil))
+    assert_equal("{\"a\"=>1}", Liquid::Utils.to_s({ "a" => 1 }))
+  end
+end