Right to the point...

Foobar has 2 very nice features:
1. one can "play a directory" (all files within are listed in foobar's playlist)
2. one can play a cue sheet (the files to which the cue sheet refers are played with pregap info from the cue sheet)

The 'problem' comes when these 2 features are used together: when you play an album directory containing both the album tracks AND the album Cue sheet, Foobar will play the album twice. (for the simple reason that first all tracks of that directory are added to Foobar's playlist, and also the Cue sheet of that directory, and that Cue sheet causes all tracks AGAIN to be added to the playlist).

I hope I've been clear. Any chance to have this 'fixed'?

As they say: One fool can ask more questions than a hundred wise men can 'answer' (in this case 'implement').

I am not sure this is a "fix" but I deleted the big mp3 file and just played the cue sheet files. I went down the playlist and when I found the "big" mp3 file I right clicked and deleted it from the playlist. Like I said it is not a fix, only a solution. It then just played the files inside the mp3 via the cue sheet with the pre-gaps.

If you just want the cue sheet added to your playlist, then don't add the mp3s... Either add the cue sheets by individually selecting them from add file and not using add directory, or, change the "Restrict incoming files to:" box in the prefs to be *.cue, before adding directories that contain cue sheets.

Yes, in fact I know these solutions.
What I had in mind as a more elegant solution (but again, I am not the one who has to implement it ) was the following:
when a cue sheet adds an album to the playlist, Foobar could check whether this album is already queued in the filelist, and spontaneously eliminate this 'overlap'.

@ xbenchman:

you can just open a cue file in foobar (then there is no need to remove any MP3s)

Not everyone would want that "solution". I certainly wouldn't.

in core setting, restrict incoming file to *.mp3;*.ape