🚨 SASL: add_authenticator warns on reassignment [🚧 test]

Author: nevans

lib/net/imap/sasl/authenticators.rb

@@ -20,15 +20,24 @@ def authenticators; @authenticators.dup end
     # {SASL mechanism}[https://www.iana.org/assignments/sasl-mechanisms/sasl-mechanisms.xhtml]
     # implemented by +authenticator+ (for instance, <tt>"PLAIN"</tt>).
     #
+    # If +mechanism+ refers to an existing authenticator, a warning will be
+    # printed and the old authenticator will be replaced.
+    #
     # The +authenticator+ must respond to +#new+ (or #call), receiving the
     # authenticator configuration and return a configured authentication session.
     # The authenticator session must respond to +#process+, receiving the server's
     # challenge and returning the client's response.
     #
     # See PlainAuthenticator, XOauth2Authenticator, and DigestMD5Authenticator for
     # examples.
-    def add_authenticator(mechanism, authenticator)
-      @authenticators[mechanism.upcase] = authenticator
+    def add_authenticator(mechanism, authenticator, warn_overwrite: true)
+      mechanism = mechanism.to_str
+      upcased = mechanism.upcase
+      if warn_overwrite && (original = authenticators[upcased])
+        warn("%p: replacing %p authenticator: %p" % [ self, upcased, original],
+             uplevel: 1)
+      end
+      @authenticators[upcased] = authenticator
     end
 
     # :call-seq: