[ruby/pp] Update pp for Set to use new inspect format

(ruby/pp#43)

Ruby 3.5 will use `Set[1, 2, 3]`. This updates pp to use the same format.

ruby/pp@507eebf711

Author: jeremyevans

lib/pp.rb

@@ -452,18 +452,16 @@ def pretty_print_cycle(q) # :nodoc:
 end
 class Set # :nodoc:
   def pretty_print(pp)  # :nodoc:
-    pp.group(1, '#<Set:', '>') {
-      pp.breakable
-      pp.group(1, '{', '}') {
-        pp.seplist(self) { |o|
-          pp.pp o
-        }
+    pp.group(1, "#{self.class.name}[", ']') {
+      pp.seplist(self) { |o|
+        pp.pp o
       }
     }
   end
 
   def pretty_print_cycle(pp)    # :nodoc:
-    pp.text sprintf('#<Set: {%s}>', empty? ? '' : '...')
+    name = self.class.name
+    pp.text(empty? ? "#{name}[]" : "#{name}[...]")
   end
 end if set_pp
 

test/test_pp.rb

@@ -2,11 +2,14 @@
 
 require 'pp'
 require 'delegate'
+require 'set'
 require 'test/unit'
 require 'ruby2_keywords'
 
 module PPTestModule
 
+SetPP = Set.instance_method(:pretty_print).source_location[0].end_with?("/pp.rb")
+
 class PPTest < Test::Unit::TestCase
   def test_list0123_12
     assert_equal("[0, 1, 2, 3]\n", PP.pp([0,1,2,3], ''.dup, 12))
@@ -16,6 +19,10 @@ def test_list0123_11
     assert_equal("[0,\n 1,\n 2,\n 3]\n", PP.pp([0,1,2,3], ''.dup, 11))
   end
 
+  def test_set
+    assert_equal("Set[0, 1, 2, 3]\n", PP.pp(Set[0,1,2,3], ''.dup, 16))
+  end if SetPP
+
   OverriddenStruct = Struct.new("OverriddenStruct", :members, :class)
   def test_struct_override_members # [ruby-core:7865]
     a = OverriddenStruct.new(1,2)
@@ -164,6 +171,12 @@ def test_hash
     assert_equal("#{a.inspect}\n", PP.pp(a, ''.dup))
   end
 
+  def test_set
+    s = Set[]
+    s.add s
+    assert_equal("Set[Set[...]]\n", PP.pp(s, ''.dup))
+  end if SetPP
+
   S = Struct.new("S", :a, :b)
   def test_struct
     a = S.new(1,2)