progressbar does not allow update of 0

[nchammas]

with click.progressbar(length=5) as progress_bar:
    progress_bar.update(0)

This throws a float division by zero error, which I believe is caused by this line here.

The reason I ran into this is because I'm trying to use progressbar to track the status of remote resources which do work at unpredictable intervals. I pass in something like work_remaining_start - work_remaining_end to progress_bar.update() in a loop that periodically checks these remote resources, and sometimes this difference is 0.

Does it make sense for update() to accept a step of 0?

[nchammas]

One good reason to allow this, at least for my use case, is that you can update the "current item" while you are waiting for work to be done, like a heartbeat.

For example:

with click.progressbar(length=5, item_show_func=lambda x: current_time()) as progress_bar:
    wait_some_time()
    work_done = check_remote_resource_for_progress()
    progress_bar.update(work_done)

So even if no work was done on a given iteration, you can still update the progress bar with something like the current time to indicate that things are still working.

If I understand correctly, show_eta doesn't kick in until after the first step has been made, and it probably is unreliable for this situation where you are waiting on remote resources to do work.

An alternative solution for this "heartbeat" use case may be to add an option similar to show_eta which shows a timer that simply counts up.

[fdavis]

I think @nchammas is right and we can just default to 0 instead of doing that division if this is called with 0

https://github.com/mitsuhiko/click/blob/89d3bfda52d151762e732738b828312a240bf89e/click/_termui_impl.py#L229