✨ Add #utf8_enabled?

This returns whether UTF-8 string encoding has been enabled for the
connection.

Author: nevans

lib/net/imap.rb

@@ -326,6 +326,9 @@ module Net
   #
   #   <em>In general, #capable? should be used rather than explicitly sending a
   #   +CAPABILITY+ command to the server.</em>
+  # - #enable: Enables backwards incompatible server extensions.
+  #   <em>Requires the +ENABLE+ or +IMAP4rev2+ capability.</em>
+  # - #utf8_enabled?: Returns whether UTF-8 string encoding has been enabled.
   #
   # === Handling server responses
   #
@@ -552,6 +555,7 @@ module Net
   # ==== RFC6855: <tt>UTF8=ACCEPT</tt>, <tt>UTF8=ONLY</tt>
   #
   # - See #enable for information about support for UTF-8 string encoding.
+  # - #utf8_enabled?: Returns whether UTF-8 string encoding has been enabled.
   #
   # ==== RFC7162: +CONDSTORE+
   #
@@ -3167,6 +3171,11 @@ def enable(*capabilities)
       end
     end
 
+    # Returns whether UTF-8 string encoding has been enabled for the connection.
+    #
+    # See #enable.
+    def utf8_enabled?; @utf8_strings end
+
     # Sends an {IDLE command [RFC2177 §3]}[https://www.rfc-editor.org/rfc/rfc6851#section-3]
     # {[IMAP4rev2 §6.3.13]}[https://www.rfc-editor.org/rfc/rfc9051#section-6.3.13]
     # that waits for notifications of new or expunged messages.  Yields

lib/net/imap/command_data.rb

@@ -86,7 +86,7 @@ def send_string_data(str, tag = nil)
     # * ASCII only (for any ASCII compatible encoding)
     # * or valid UTF-8 (when the connection supports it)
     def text_encodable?(str)
-      str.ascii_only? || (@utf8_strings &&
+      str.ascii_only? || (utf8_enabled? &&
                           str.encoding == Encoding::UTF_8 &&
                           str.valid_encoding?)
     end

test/net/imap/test_imap.rb

@@ -1018,6 +1018,7 @@ def imap.test_args(*args) = send_command("TEST", *args)
 
       # After enabling UTF-8 strings
       imap.enable(:utf8)
+      assert imap.utf8_enabled?
       server.commands.pop.args => ["UTF8=ACCEPT"]
 
       imap.test_args "quoted-utf8", "αβγδε"

test/net/imap/test_imap_enable.rb

@@ -14,14 +14,18 @@ def test_enable
     ) do |server, imap|
       cmdq = server.commands
 
+      refute imap.utf8_enabled?
+
       enabled = imap.enable(%w[CONDSTORE x-pig-latin])
       assert_equal "RUBY0001 ENABLE CONDSTORE x-pig-latin", cmdq.pop.raw.strip
       assert_equal %w[CONDSTORE], enabled
+      refute imap.utf8_enabled?
 
       enabled = imap.enable(:utf8, "condstore QResync")
       assert_equal("RUBY0002 ENABLE UTF8=ACCEPT condstore QResync",
                    cmdq.pop.raw.strip)
       assert_equal %w[UTF8=ACCEPT], enabled
+      assert imap.utf8_enabled?
 
       assert_empty cmdq
 
@@ -35,6 +39,21 @@ def test_enable
     end
   end
 
+  test("enable IMAP4rev2") do
+    with_fake_server(
+      with_extensions: %i[ENABLE CONDSTORE IMAP4rev2 UTF8=ACCEPT],
+      capabilities_enablable: %w[CONDSTORE UTF8=ACCEPT IMAP4rev2]
+    ) do |server, imap|
+      cmdq = server.commands
+
+      enabled = imap.enable("IMAP4rev2")
+      assert_equal "RUBY0001 ENABLE IMAP4rev2", cmdq.pop.raw.strip
+      assert imap.utf8_enabled?
+
+      assert_empty cmdq
+    end
+  end
+
   test("missing server ENABLED response") do
     with_fake_server do |server, imap|
       server.on "ENABLE", &:done_ok