add method(compact, compact!) and test of Hash to mruby-hash-ext

mrbgems/mruby-hash-ext/mrblib/hash.rb

@@ -114,6 +114,40 @@ class Hash
 
   alias update merge!
 
+  ##
+  # call-seq:
+  #    hsh.compact     -> new_hsh
+  #
+  # Returns a new hash with the nil values/key pairs removed
+  #
+  #    h = { a: 1, b: false, c: nil }
+  #    h.compact     #=> { a: 1, b: false }
+  #    h             #=> { a: 1, b: false, c: nil }
+  #
+  def compact
+    result = self.dup
+    result.compact!
+    result
+  end
+
+  ##
+  # call-seq:
+  #    hsh.compact!    -> hsh
+  #
+  # Removes all nil values from the hash. Returns the hash.
+  #
+  #    h = { a: 1, b: false, c: nil }
+  #    h.compact!     #=> { a: 1, b: false }
+  #
+  def compact!
+    result = self.select { |k, v| !v.nil? }
+    if result.size == self.size
+      nil
+    else
+      self.replace(result)
+    end
+  end
+
   ##
   #  call-seq:
   #     hsh.fetch(key [, default] )       -> obj

mrbgems/mruby-hash-ext/test/hash.rb

@@ -82,6 +82,20 @@ assert('Hash#values_at') do
   assert_equal keys, h.values_at(*keys)
 end
 
+assert('Hash#compact') do
+  h = { "cat" => "feline", "dog" => nil, "cow" => false }
+
+  assert_equal({ "cat" => "feline", "cow" => false }, h.compact)
+  assert_equal({ "cat" => "feline", "dog" => nil, "cow" => false }, h)
+end
+
+assert('Hash#compact!') do
+  h = { "cat" => "feline", "dog" => nil, "cow" => false }
+
+  h.compact!
+  assert_equal({ "cat" => "feline", "cow" => false }, h)
+end
+
 assert('Hash#fetch') do
   h = { "cat" => "feline", "dog" => "canine", "cow" => "bovine" }
   assert_equal "feline", h.fetch("cat")