Deprecate taint/trust and related methods, and make the methods no-ops

This removes the related tests, and puts the related specs behind
version guards.  This affects all code in lib, including some
libraries that may want to support older versions of Ruby.

Author: jeremyevans

ext/pathname/pathname.c

@@ -110,7 +110,6 @@ path_initialize(VALUE self, VALUE arg)
     str = rb_obj_dup(str);
 
     set_strpath(self, str);
-    OBJ_INFECT(self, str);
     return self;
 }
 
@@ -134,31 +133,25 @@ path_freeze(VALUE self)
  * call-seq:
  *   pathname.taint -> obj
  *
- * Taints this Pathname.
- *
- * See Object.taint.
+ * Returns pathname.  This method is deprecated and will be removed in Ruby 3.2.
  */
 static VALUE
 path_taint(VALUE self)
 {
-    rb_call_super(0, 0);
-    rb_obj_taint(get_strpath(self));
+    rb_warning("Pathname#taint is deprecated and will be removed in Ruby 3.2.");
     return self;
 }
 
 /*
  * call-seq:
  *   pathname.untaint -> obj
  *
- * Untaints this Pathname.
- *
- * See Object.untaint.
+ * Returns pathname.  This method is deprecated and will be removed in Ruby 3.2.
  */
 static VALUE
 path_untaint(VALUE self)
 {
-    rb_call_super(0, 0);
-    rb_obj_untaint(get_strpath(self));
+    rb_warning("Pathname#untaint is deprecated and will be removed in Ruby 3.2.");
     return self;
 }
 
@@ -308,7 +301,6 @@ path_sub_ext(VALUE self, VALUE repl)
     }
     str2 = rb_str_subseq(str, 0, ext-p);
     rb_str_append(str2, repl);
-    OBJ_INFECT(str2, str);
     return rb_class_new_instance(1, &str2, rb_obj_class(self));
 }
 

test/pathname/test_pathname.rb

@@ -592,39 +592,6 @@ def test_null_character
     assert_raise(ArgumentError) { Pathname.new("\0") }
   end
 
-  def test_taint
-    obj = Pathname.new("a"); assert_same(obj, obj.taint)
-    obj = Pathname.new("a"); assert_same(obj, obj.untaint)
-
-    assert_equal(false, Pathname.new("a"          )           .tainted?)
-    assert_equal(false, Pathname.new("a"          )      .to_s.tainted?)
-    assert_equal(true,  Pathname.new("a"          ).taint     .tainted?)
-    assert_equal(true,  Pathname.new("a"          ).taint.to_s.tainted?)
-    assert_equal(true,  Pathname.new("a".dup.taint)           .tainted?)
-    assert_equal(true,  Pathname.new("a".dup.taint)      .to_s.tainted?)
-    assert_equal(true,  Pathname.new("a".dup.taint).taint     .tainted?)
-    assert_equal(true,  Pathname.new("a".dup.taint).taint.to_s.tainted?)
-
-    str = "a".dup
-    path = Pathname.new(str)
-    str.taint
-    assert_equal(false, path     .tainted?)
-    assert_equal(false, path.to_s.tainted?)
-  end
-
-  def test_untaint
-    obj = Pathname.new("a"); assert_same(obj, obj.untaint)
-
-    assert_equal(false, Pathname.new("a").taint.untaint     .tainted?)
-    assert_equal(false, Pathname.new("a").taint.untaint.to_s.tainted?)
-
-    str = "a".dup.taint
-    path = Pathname.new(str)
-    str.untaint
-    assert_equal(true, path     .tainted?)
-    assert_equal(true, path.to_s.tainted?)
-  end
-
   def test_freeze
     obj = Pathname.new("a"); assert_same(obj, obj.freeze)
 
@@ -638,20 +605,6 @@ def test_freeze
     assert_equal(false, Pathname.new("a".freeze).freeze.to_s.frozen?)
   end
 
-  def test_freeze_and_taint
-    obj = Pathname.new("a")
-    obj.freeze
-    assert_equal(false, obj.tainted?)
-    assert_raise(FrozenError) { obj.taint }
-
-    obj = Pathname.new("a")
-    obj.taint
-    assert_equal(true, obj.tainted?)
-    obj.freeze
-    assert_equal(true, obj.tainted?)
-    assert_nothing_raised { obj.taint }
-  end
-
   def test_to_s
     str = "a"
     obj = Pathname.new(str)