🔧 Allow Hash input to Config.[]

lib/net/imap/config.rb

@@ -66,9 +66,19 @@ def self.default; @default end
       # The global config object.  Also available from Net::IMAP.config.
       def self.global; @global end
 
-      def self.[](config) # :nodoc: unfinished API
+      # :call-seq:
+      #  Net::IMAP::Config[hash]   -> new frozen config
+      #  Net::IMAP::Config[config] -> same config
+      #
+      # Given a Hash, creates a new _frozen_ config which inherits from
+      # Config.global.  Use Config.new for an unfrozen config.
+      #
+      # Given a config, returns that same config.
+      def self.[](config)
         if config.is_a?(Config) || config.nil? && global.nil?
           config
+        elsif config.respond_to?(:to_hash)
+          new(global, **config).freeze
         else
           raise TypeError, "no implicit conversion of %s to %s" % [
             config.class, Config

test/net/imap/test_config.rb

@@ -135,10 +135,22 @@ class ConfigTest < Test::Unit::TestCase
     assert_equal false, child.debug?
   end
 
+  test ".[] with a hash" do
+    config = Config[{responses_without_block: :raise, sasl_ir: false}]
+    assert config.frozen?
+    refute config.sasl_ir?
+    assert config.inherited?(:debug)
+    refute config.inherited?(:sasl_ir)
+    assert_same Config.global, config.parent
+    assert_same :raise, config.responses_without_block
+  end
+
   test ".new always sets a parent" do
     assert_same Config.global,  Config.new.parent
     assert_same Config.default, Config.new(Config.default).parent
     assert_same Config.global,  Config.new(Config.global).parent
+    assert_equal true, Config.new({debug: true}, debug: false).parent.debug?
+    assert_equal true, Config.new({debug: true}, debug: false).parent.frozen?
   end
 
   test "#inherited? and #reset(attr)" do