Re: [PATCH] Add checks for new and tmp directories to mx_is_maildir()

On Wed, Feb 04, 2026 at 02:39:22PM +0100, Alejandro Colomar via Mutt-dev wrote:
> Hi Crystal,
> 
> On 2026-02-04T10:30:52+0000, Crystal Kolipe via Mutt-dev wrote:
> > On Wed, Feb 04, 2026 at 01:04:20PM +0800, Kevin J. McCarthy wrote:
> > > This function is used by mx_get_magic() to check if a path is a
> > > maildir mailbox.  I believe it was only looking for "cur" to save on
> > > stat calls.
> > > 
> > > However, this can cause misbehavior in some cases.  The browser won't
> > > enter a (non-maildir) directory that contains only a subdirectory
> > > "cur".  On the other other hand, mutt relies on the "tmp" and "new"
> > > subdirectories existing or fails operations, such as append to
> > > mailbox, or postponing mail.
> > > ---
> > > Just going through some branches I'd accumulated over the  past few years.
> > > 
> > > I'm sure I don't need to ask for feedback, but this is a tradeoff of a
> > > couple stat calls for correct behavior in some less common situations.
> > > Thoughts?
> > 
> > This could plausibly break things for anyone who has written one or more old
> > maildir directories to a read-only medium, and to save space has removed the
> > empty 'new' and 'tmp' directories.
> > 
> > On the other hand, implementing this change would discourange users from doing
> > the same thing going forward, so overall I think it's the correct approach.
> > 
> > Would it make sense to drop the check for 'new' and 'tmp' IFF 'cur' can only
> > be opened read-only?
> 
> I'd keep it simple.  Complexity is dangerous, and users that do this
> should be aware of what they're doing, and fix their maildir.

Well, if it's been written to a BD-R, for example, fixing it means re-writing
it to a new disc.  That was the type of scenario I was thinking of, not a
regular partition mounted read-only, which could easy be changed.