Libguestfs - Jan 2023 - [libnbd PATCH v2 3/3] nbdsh: Improve --help and initial banner contents.

On Fri, Nov 04, 2022 at 04:18:31PM -0500, Eric Blake
wrote:
> Document all options in --help output.  If -n is not in use, then
> enhance the banner to print the current state of h, and further tailor
> the advice given on useful next steps to take to mention opt_go when
> using --opt-mode.
I had to partially revert this patch (reverting most of it) because it
unfortunately breaks the implicit handle creation :-(

https://gitlab.com/nbdkit/libnbd/-/commit/5a02c7d2cc6a201f9e5531c0c20c2f3c22b805a2

I'm not actually sure how to do this correctly in Python.  I made
several attempts, but I don't think Python is very good about having a
variable which is only defined on some paths -- maybe it's not
possible at all.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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On Tue, Jan 31, 2023 at 12:34 AM Richard W.M. Jones <rjones at redhat.com>
wrote:
>
> On Fri, Nov 04, 2022 at 04:18:31PM -0500, Eric Blake wrote:
> > Document all options in --help output.  If -n is not in use, then
> > enhance the banner to print the current state of h, and further tailor
> > the advice given on useful next steps to take to mention opt_go when
> > using --opt-mode.
>
> I had to partially revert this patch (reverting most of it) because it
> unfortunately breaks the implicit handle creation :-(
>
>
https://gitlab.com/nbdkit/libnbd/-/commit/5a02c7d2cc6a201f9e5531c0c20c2f3c22b805a2
>
> I'm not actually sure how to do this correctly in Python.  I made
> several attempts, but I don't think Python is very good about having a
> variable which is only defined on some paths -- maybe it's not
> possible at all.
Can you share the error when it breaks?

I'm not sure what is the issue, but usually if you have a global
variable created only in
some flows, adding:

    thing = None

At the start of the module makes sure that the name exists later,
regardless of the flow
taken. Code can take the right action based on:

    if thing is None:
        ...

Nir