Add and document flags from RFC9051

lib/net/imap/flags.rb

@@ -3,62 +3,232 @@
 module Net
   class IMAP < Protocol
 
-    # :category: Message Flags
+    # -------------------------------------------------------------------------
+    # :section: Message Flags: system flags
     #
-    # Flag indicating a message has been seen.
+    # A message has a list of zero or more named tokens, known as "flags",
+    # associated with it. A flag is set by its addition to this list and is
+    # cleared by its removal. There are two types of flags in IMAP4rev2: system
+    # flags and keywords. A flag of either type can be permanent or
+    # session-only.
+    #
+    # A "system flag" is a message flag name that is predefined in the IMAP
+    # specification and begins with "\".  +Net::IMAP+ returns all system flags
+    # as symbols, without the "\" prefix.
+    #
+    # The descriptions here were copied from the IMAP4rev2 specification:
+    # [RFC-9051 § 2.3.2](https://www.rfc-editor.org/rfc/rfc9051.html#section-2.3.2)
+    #
+    # See [RFC-3501 § 2.3.2](https://www.rfc-editor.org/rfc/rfc3501.html#section-2.3.2)
+    # for a description of the flags message attribute and system flag semantics
+    # in IMAP4rev1.
+    # -------------------------------------------------------------------------
+
+    # Flag indicating a message has been read.
     SEEN = :Seen
 
-    # :category: Message Flags
-    #
     # Flag indicating a message has been answered.
     ANSWERED = :Answered
 
-    # :category: Message Flags
-    #
-    # Flag indicating a message has been flagged for special or urgent
+    # A message flag indicating a message has been flagged for special or urgent
     # attention.
+    #
+    # Also a mailbox special use attribute, which indicates that this mailbox
+    # presents all messages marked in some way as "important".  When this
+    # special use is supported, it is likely to represent a virtual mailbox
+    # collecting messages (from other mailboxes) that are marked with the
+    # "\Flagged" message flag.
     FLAGGED = :Flagged
 
-    # :category: Message Flags
-    #
     # Flag indicating a message has been marked for deletion.  This
     # will occur when the mailbox is closed or expunged.
     DELETED = :Deleted
 
-    # :category: Message Flags
-    #
     # Flag indicating a message is only a draft or work-in-progress version.
     DRAFT = :Draft
 
-    # :category: Message Flags
-    #
     # Flag indicating that the message is "recent," meaning that this
     # session is the first session in which the client has been notified
     # of this message.
+    #
+    # This flag was defined by
+    # IMAP4rev1 [RFC-3501](https://www.rfc-editor.org/rfc/rfc3501.html),
+    # and has been deprecated by
+    # IMAP4rev2 [RFC-9051](https://www.rfc-editor.org/rfc/rfc9051.html).
     RECENT = :Recent
 
-    # :category: Mailbox Flags
+    # -------------------------------------------------------------------------
+    # :section: Mailbox Name Attributes, Base attributes
+    # Mailbox name attributes will be returned in LIST responses.  Base
+    # attributes must be returned according to the server's capabilities.
     #
-    # Flag indicating that a mailbox context name cannot contain
-    # children.
-    NOINFERIORS = :Noinferiors
+    # IMAP4 specifies that all mailbox name attributes, including future
+    # extensions, begin with "\".  +Net::IMAP+ returns all mailbox attributes as
+    # symbols, without the "\" prefix.
+    #
+    # The descriptions here were copied from the IMAP4rev2 specification:
+    # [RFC9051 § 7.3.1](https://www.rfc-editor.org/rfc/rfc9051.html#section-7.3.1).
+    #
+    # Other mailbox name attributes can be found in the [IANA IMAP Mailbox Name
+    # Attributes registry](https://www.iana.org/assignments/imap-mailbox-name-attributes/imap-mailbox-name-attributes.xhtml)].
+    # -------------------------------------------------------------------------
+
+    # The "\NonExistent" attribute indicates that a mailbox name does not refer
+    # to an existing mailbox. Note that this attribute is not meaningful by
+    # itself, as mailbox names that match the canonical LIST pattern but don't
+    # exist must not be returned unless one of the two conditions listed below
+    # is also satisfied:
+    #
+    # 1. The mailbox name also satisfies the selection criteria (for example,
+    #    it is subscribed and the "SUBSCRIBED" selection option has been
+    #    specified).
+    #
+    # 2. "RECURSIVEMATCH" has been specified, and the mailbox name has at least
+    #    one descendant mailbox name that does not match the LIST pattern and
+    #    does match the selection criteria.
+    #
+    # In practice, this means that the "\NonExistent" attribute is usually
+    # returned with one or more of "\Subscribed", "\Remote", "\HasChildren", or
+    # the CHILDINFO extended data item.
+    #
+    # The client must treat the presence of the \NonExistent attribute as if the
+    # \NoSelect attribute was also sent by the server
+    NONEXISTENT = :NonExistent
 
-    # :category: Mailbox Flags
+    # Mailbox attribute indicating it is not possible for any child levels of
+    # hierarchy to exist under this name; no child levels exist now and none can
+    # be created in the future children.
     #
-    # Flag indicating that a mailbox is not selected.
+    # The client must treat the presence of the \NoInferiors attribute as if the
+    # \HasNoChildren attribute was also sent by the server
+    NOINFERIORS = :Noinferiors
+
+    # Mailbox attribute indicating it is not possible to use this name as a
+    # selectable mailbox.
     NOSELECT = :Noselect
 
-    # :category: Mailbox Flags
+    # The presence of this attribute indicates that the mailbox has child
+    # mailboxes. A server SHOULD NOT set this attribute if there are child
+    # mailboxes and the user does not have permission to access any of them.  In
+    # this case, \HasNoChildren SHOULD be used. In many cases, however, a server
+    # may not be able to efficiently compute whether a user has access to any
+    # child mailboxes. Note that even though the \HasChildren attribute for a
+    # mailbox must be correct at the time of processing the mailbox, a client
+    # must be prepared to deal with a situation when a mailbox is marked with
+    # the \HasChildren attribute, but no child mailbox appears in the response
+    # to the LIST command. This might happen, for example, due to child
+    # mailboxes being deleted or made inaccessible to the user (using access
+    # control) by another client before the server is able to list them.
+    #
+    # It is an error for the server to return both a \HasChildren and a
+    # \HasNoChildren attribute in the same LIST response. A client that
+    # encounters a LIST response with both \HasChildren and \HasNoChildren
+    # attributes present should act as if both are absent in the LIST response.
+    HAS_CHILDREN = :HasChildren
+
+    # The presence of this attribute indicates that the mailbox has NO child
+    # mailboxes that are accessible to the currently authenticated user.
+    #
+    # It is an error for the server to return both a \HasChildren and a
+    # \HasNoChildren attribute in the same LIST response. A client that
+    # encounters a LIST response with both \HasChildren and \HasNoChildren
+    # attributes present should act as if both are absent in the LIST response.
+    #
+    # Note: the \HasNoChildren attribute should not be confused with the
+    # \NoInferiors attribute, which indicates that no child mailboxes exist now
+    # and none can be created in the future.
+    HAS_NO_CHILDREN = :HasNoChildren
+
+    # The mailbox has been marked "interesting" by the server; the mailbox
+    # probably contains messages that have been added since the last time the
+    # mailbox was selected.
     #
-    # Flag indicating that a mailbox has been marked "interesting" by
-    # the server; this commonly indicates that the mailbox contains
-    # new messages.
+    # If it is not feasible for the server to determine whether or not the
+    # mailbox is "interesting", the server SHOULD NOT send either \Marked or
+    # \Unmarked. The server MUST NOT send more than one of \Marked, \Unmarked,
+    # and \Noselect for a single mailbox, and it MAY send none of these.
     MARKED = :Marked
 
-    # :category: Mailbox Flags
+    # The mailbox does not contain any additional messages since the last time
+    # the mailbox was selected.
     #
-    # Flag indicating that the mailbox does not contains new messages.
+    # If it is not feasible for the server to determine whether or not the
+    # mailbox is "interesting", the server SHOULD NOT send either \Marked or
+    # \Unmarked. The server MUST NOT send more than one of \Marked, \Unmarked,
+    # and \Noselect for a single mailbox, and it MAY send none of these.
     UNMARKED = :Unmarked
 
+    # The mailbox name was subscribed to using the SUBSCRIBE command.
+    SUBSCRIBED = :Subscribed
+
+    # The mailbox is a remote mailbox.
+    REMOTE = :Remove
+
+    # -------------------------------------------------------------------------
+    # :section: Mailbox Name Attributes, Special Use
+    # Mailbox name attributes will be returned in LIST responses.  In addition
+    # to the base mailbox name attributes defined above, an IMAP server MAY also
+    # include any or all of the following attributes that denote "role" (or
+    # "special-use") of a mailbox. These attributes are included along with base
+    # attributes defined above. A given mailbox may have none, one, or more than
+    # one of these attributes. In some cases, a special use is advice to a
+    # client about what to put in that mailbox. In other cases, it's advice to a
+    # client about what to expect to find there.
+    #
+    # IMAP4 specifies that all mailbox name attributes, including future
+    # extensions, begin with "\".  +Net::IMAP+ returns all mailbox attributes as
+    # symbols, without the "\" prefix.
+    #
+    # The descriptions here were copied from the IMAP4rev2 specification:
+    # [RFC-9051 § 7.3.1](https://www.rfc-editor.org/rfc/rfc9051.html#section-7.3.1).
+    #
+    # Other mailbox name attributes can be found in the [IANA IMAP Mailbox Name
+    # Attributes registry](https://www.iana.org/assignments/imap-mailbox-name-attributes/imap-mailbox-name-attributes.xhtml)].
+    # -------------------------------------------------------------------------
+
+    # Mailbox attribute indicating that this mailbox presents all messages in
+    # the user's message store. Implementations MAY omit some messages, such as,
+    # perhaps, those in \Trash and \Junk. When this special use is supported, it
+    # is almost certain to represent a virtual mailbox
+    ALL = :All
+
+    # Mailbox attribute indicating that this mailbox is used to archive
+    # messages. The meaning of an "archival" mailbox is server dependent;
+    # typically, it will be used to get messages out of the inbox, or otherwise
+    # keep them out of the user's way, while still making them accessible
+    ARCHIVE = :Archive
+
+    # Mailbox attribute indicating that this mailbox is used to hold draft
+    # messages -- typically, messages that are being composed but have not yet
+    # been sent. In some server implementations, this might be a virtual
+    # mailbox, containing messages from other mailboxes that are marked with the
+    # "\Draft" message flag. Alternatively, this might just be advice that a
+    # client put drafts here
+    DRAFTS = :Drafts
+
+    # FLAGGED is defined with the system flags section.
+
+    # Mailbox attribute indicating that this mailbox is where messages deemed to
+    # be junk mail are held. Some server implementations might put messages here
+    # automatically.  Alternatively, this might just be advice to a client-side
+    # spam filter.
+    JUNK = :Junk
+
+    # Mailbox attribute indicating that this mailbox is used to hold copies of
+    # messages that have been sent. Some server implementations might put
+    # messages here automatically. Alternatively, this might just be advice that
+    # a client save sent messages here.
+    SENT = :Sent
+
+    # Mailbox attribute indicating that this mailbox is used to hold messages
+    # that have been deleted or marked for deletion. In some server
+    # implementations, this might be a virtual mailbox, containing messages from
+    # other mailboxes that are marked with the "\Deleted" message flag.
+    # Alternatively, this might just be advice that a client that chooses not to
+    # use the IMAP "\Deleted" model should use as its trash location. In server
+    # implementations that strictly expect the IMAP "\Deleted" model, this
+    # special use is likely not to be supported.
+    TRASH = :Trash
+
   end
 end