Add XOAuth2 authenticator

lib/net/imap/authenticators.rb

@@ -45,3 +45,4 @@ def authenticators
 require_relative "authenticators/login"
 require_relative "authenticators/cram_md5"
 require_relative "authenticators/digest_md5"
+require_relative "authenticators/xoauth2"

lib/net/imap/authenticators/xoauth2.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class Net::IMAP::XOauth2Authenticator
+  def process(_data)
+    build_oauth2_string(@user, @oauth2_token)
+  end
+
+  private
+
+  def initialize(user, oauth2_token)
+    @user = user
+    @oauth2_token = oauth2_token
+  end
+
+  def build_oauth2_string(user, oauth2_token)
+    format("user=%s\1auth=Bearer %s\1\1".encode('us-ascii'), user, oauth2_token)
+  end
+
+  Net::IMAP.add_authenticator 'XOAUTH2', self
+end

test/net/imap/test_imap_authenticators.rb

@@ -29,6 +29,17 @@ def test_plain_no_null_chars
     assert_raise(ArgumentError) { plain("u", "p", authzid: "bad\0authz") }
   end
 
+  # ----------------------
+  # XOAUTH2
+  # ----------------------
+
+  def test_xoauth2
+    assert_equal(
+      "user=username\1auth=Bearer token\1\1".encode('us-ascii'),
+      Net::IMAP::XOauth2Authenticator.new("username", "token").process(nil)
+    )
+  end
+
   # ----------------------
   # LOGIN (obsolete)
   # ----------------------
@@ -128,5 +139,4 @@ def test_digest_md5_authenticator
       )
     )
   end
-
 end