✨ Add STATUS HIGHESTMODSEQ (RFC7162, CONDSTORE)

This doesn't actually require explicit support, because `HIGHESTMODSEQ`
is simply another numeric status attribute, and we already parse
`number` as the default (without using `ExtensionData`).

Author: nevans

lib/net/imap.rb

@@ -502,6 +502,10 @@ module Net
   #
   # - See #enable for information about support for UTF-8 string encoding.
   #
+  # ==== RFC7162: +CONDSTORE+
+  #
+  # - Updates #status with the +HIGHESTMODSEQ+ status attribute.
+  #
   # ==== RFC8438: <tt>STATUS=SIZE</tt>
   # - Updates #status with the +SIZE+ status attribute.
   #
@@ -1689,7 +1693,7 @@ def lsub(refname, mailbox)
       end
     end
 
-    # Sends a {STATUS commands [IMAP4rev1 §6.3.10]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.3.10]
+    # Sends a {STATUS command [IMAP4rev1 §6.3.10]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.3.10]
     # and returns the status of the indicated +mailbox+. +attr+ is a list of one
     # or more attributes whose statuses are to be requested.
     #
@@ -1716,10 +1720,13 @@ def lsub(refname, mailbox)
     #     The approximate size of the mailbox---must be greater than or equal to
     #     the sum of all messages' +RFC822.SIZE+ fetch item values.
     #
+    # +HIGHESTMODSEQ+::
+    #    The highest mod-sequence value of all messages in the mailbox.  See
+    #    +CONDSTORE+ {[RFC7162]}[https://www.rfc-editor.org/rfc/rfc7162.html].
+    #
     # +MAILBOXID+::
-    #     A server-allocated unique _string_ identifier for the mailbox.
-    #     See +OBJECTID+
-    #     {[RFC8474]}[https://www.rfc-editor.org/rfc/rfc8474.html#section-4].
+    #     A server-allocated unique _string_ identifier for the mailbox.  See
+    #     +OBJECTID+ {[RFC8474]}[https://www.rfc-editor.org/rfc/rfc8474.html].
     #
     # +RECENT+::
     #     The number of messages with the <tt>\Recent</tt> flag.
@@ -1741,6 +1748,9 @@ def lsub(refname, mailbox)
     #
     # +DELETED+ requires the server's capabilities to include +IMAP4rev2+.
     #
+    # +HIGHESTMODSEQ+ requires the server's capabilities to include +CONDSTORE+
+    # {[RFC7162]}[https://www.rfc-editor.org/rfc/rfc7162.html].
+    #
     # +MAILBOXID+ requires the server's capabilities to include +OBJECTID+
     # {[RFC8474]}[https://www.rfc-editor.org/rfc/rfc8474.html].
     def status(mailbox, attr)

lib/net/imap/response_parser.rb

@@ -1594,6 +1594,7 @@ def status_att_val
           when "UIDVALIDITY"   then nz_number           # RFC3501, RFC9051
           when "RECENT"        then number              # RFC3501 (obsolete)
           when "SIZE"          then number64            # RFC8483, RFC9051
+          when "HIGHESTMODSEQ" then mod_sequence_valzer # RFC7162
           when "MAILBOXID"     then parens__objectid    # RFC8474
           else
             number? || ExtensionData.new(tagged_ext_val)
@@ -1966,6 +1967,10 @@ def charset; quoted? || atom end
       #                        ;; Per-message mod-sequence.
       alias permsg_modsequence mod_sequence_value
 
+      # RFC7162:
+      # mod-sequence-valzer = "0" / mod-sequence-value
+      alias mod_sequence_valzer number64
+
       def parens__modseq; lpar; _ = permsg_modsequence; rpar; _ end
 
       # RFC8474: