Re: [PATCH 2/2] tags_to_maildir_flags: Don't rename if no flags change

[Austin Clements <amdragon@MIT.EDU>]

I worry that this may compound the confusion caused by mutt's handling
of the new flag, but I suppose people aren't likely to manipulate any
of the other maildir-synchronized flags without also marking the
message as seen.  At any rate, the change is certainly correct
technically.  A few nits below.

Quoth Louis Rilling on Jul 11 at  4:36 pm:
> notmuch_message_tags_to_maildir_flags() unconditionally moves messages from
> maildir directory "new/" to maildir directory "cur/", which makes messages lose
> their "new" status in the MUA. However some users want to keep this "new"
> status after, for instance, an auto-tagging of new messages.
> 
> However, as Austin mentioned and according to the maildir specification,
> messages living in "new/" are not allowed to have flags, even if mutt allows it
> to happen. For this reason, this patch prevents moving messages from "new/" to
> "cur/", only if no flags have to be changed. It's hopefully enough to satisfy
> mutt (and maybe other MUAs showing the "new" status) users checking the "new"
> status.
> 
> Signed-off-by: Louis Rilling <l.rilling@av7.net>
> ---
>  lib/message.cc |   12 +++++++++++-
>  1 files changed, 11 insertions(+), 1 deletions(-)
> 
> diff --git a/lib/message.cc b/lib/message.cc
> index 64b6cf8..131d99b 100644
> --- a/lib/message.cc
> +++ b/lib/message.cc
> @@ -1139,7 +1139,7 @@ _get_maildir_flag_actions (notmuch_message_t *message,
>   * compute the new maildir filename.
>   *
>   * If the existing filename is in the directory "new", the new
> - * filename will be in the directory "cur".
> + * filename will be in the directory "cur", unless no flags are changed.
>   *
>   * After a sequence of ":2," in the filename, any subsequent
>   * single-character flags will be added or removed according to the
> @@ -1162,6 +1162,7 @@ _new_maildir_filename (void *ctx,
>      char *filename_new, *dir;
>      char flag_map[128];
>      int flags_in_map = 0;
> +    bool flags_changed = false;

The convention in notmuch is to use notmuch_bool_t, TRUE, and FALSE
(though, admittedly, I don't know why; avoiding C99-isms?)

>      unsigned int i;
>      char *s;
>  
> @@ -1202,6 +1203,7 @@ _new_maildir_filename (void *ctx,
>  	if (flag_map[flag] == 0) {
>  	    flag_map[flag] = 1;
>  	    flags_in_map++;
> +	    flags_changed = true;
>  	}
>      }
>  
> @@ -1210,9 +1212,17 @@ _new_maildir_filename (void *ctx,
>  	if (flag_map[flag]) {
>  	    flag_map[flag] = 0;
>  	    flags_in_map--;
> +	    flags_changed = true;
>  	}
>      }
>  
> +    /* No need to rename. Messages in new/ can be kept in new/.
> +     * Note: We don't even try to fix buggy messages having flags and living in
> +     * new/. It's not our business.
> +     */
> +    if (!flags_changed)
> +	return NULL;
> +

NULL generally indicates an error in notmuch and is currently used
that way in _new_maildir_filename, so even though the caller currently
doesn't really care, I'd lean against overloading it to indicate that
the filename doesn't need to change.  Despite the slight inefficiency,
I would recommend returning talloc_strdup (ctx, filename).

>      filename_new = (char *) talloc_size (ctx,
>  					 info - filename +
>  					 strlen (":2,") + flags_in_map + 1);