The problem is not that the new pdf output is not complete until the end of the typesetting process, the problem is that the old pdf is removed at the beginning of the typesetting process, whereas it could be removed only at the very last moment. This would be a big improvement in everyone’s workflow (overleaf uses that de facto).
I agree that luatex callbacks can be used for that purpose, but it means that each people must have some basic lua skills and will have to modify all its documents one by one. Using the ‘--lua’ options is a bit better, except that every one must still duplicate the initialization file in each document folder. Anyways, this is rather far from a user friendly one click solution.
As pointed out by Hans, adding a new command line option to luatex de facto breaks backwards compatibility somehow.
If something possibly gets broken on extremely rare occasions whereas there exists a very simple fix, this is not really a problem compared to the benefits. Moreover, using ‘--output-busy’ instead of ‘--busy’ would help, and would be more explicit as well.
This should be in the TODO list, not at the top, but not very far…
BTW, I have found luatex roadmap on the web but no task list, was I unlucky ?
JL
Yes, this does work on a per document basis, but what I request is a builtin feature that simply applies out of the box and is backwards compatible.
it's not clear what you want to achieve.... What does "busy" mean in this context ?
It means that the output file is named jobname.pdf despite it is known to be incomplete and unusable during all the typesetting process.
The output file should be named jobname.pdf only once it is really a complete pdf file.
In the meanwhile its extension is pdf(busy), which means that it is a pdf file under construct.
It's a well established rule that one can use the file jobname.pdf *after* that the luatex process ends, and even in this case it doesn't mean that
the pdf is complete and / or usable , even if the luatex process ends correctly.
If people were given a choice, this de facto rule would certainly be not so well established.
JL