# Thursday, July 7, 2016¶

## Pitfall when getting started¶

Grigorij had reported a problem when following the Getting started guide. The lino.modlib.wkhtmltopdf plugin failed to import when trying to do:

from wkhtmltopdf.utils import render_pdf_from_template


I answered too quickly that “When you see in Python that “from xxx.yyy import zzz” fails with an ImportError, then you know that package xxx is not installed. So the explanation is that wkhtmltopdf is not installed. Solution for you now is to simply pip install wkhtmltopdf.”

But that was wrong. The lino.modlib.wkhtmltopdf plugin does not require wkhtmltopdf, it requires django-wkhtmltopdf. Thanks to Hamza who found the real explanation.

I now changed lino.modlib.wkhtmltopdf so that it fails only when you actually try to print something using this method. I don’t add django-wkhtmltopdf to install_requires because the lino.modlib.wkhtmltopdf plugin is probably deprecated.

Yes, we should write automated tests that cover the Getting started guide, i.e. create a new virtualenv etc… Let’s discuss about the details… #1027

## ExtJS6 Paging buttons in detail window¶

I fixed #1023. This was just because the items of the toolbar were Ext.toolbar.Toolbar instances. They must be Ext.button.Button instances of course.

## Release to lf.org¶

I did a release to lino-framework.org, mainly in order to test my changes for #807 (2016-07-04). It will also activate the recent changes for #559 and therefore requires me to install the new linod command as a daemon process.

Before the actual release I converted lino.utils.daemoncommand from optparse to argparse. And added a comand-line –list to linod.

## Timezone tests¶

The release itself was trivial. Then, after the release, even before caring about the daemon, I had to run a rather fragile manual test: see whether datetime fields are correctly dumped and restored after the little change for #807 I made 2016-07-04. Because I was not very sure whether the test case I wrote covered everything. And it turned indeed out that there was still some bug.

I made a double dump test and looked at the first entry of the changes_changes.py file (which holds the Pythonic representations of the changes.Change instances).

In the “reference” snapshot created with old version we have:

loader.save(create_changes_change(u'1',dt(2015,11,16,6,44,59),...


This is the first (registered) change in our ticketing system. It was at 6:44 in the morning of 2015-11-16. Nobody will probably ever know in which timezone this was. We might find it out, but the change timestamps are actually not that important for us. The test

Note that also after 2016-07-04 the files themselves continue to contain naive dates. We don’t need to also write their timezone because they are always all in the same timezone. The new version just interprets them “intelligently”, converting them to aware timestamps before writing them to the database.

The first double dump test gave this:

loader.save(create_changes_change(u'1',dt(2015,11,16,4,44,59),...


loader.save(create_changes_change(u'1',dt(2015,11,16,2,44,59),...


This shows that all timestamps would get shifted by 2 hours for every dump/restore from now on. That’s not good!

What I understood only today was that dump2py was wrong when it did simply:

if isinstance(field, models.DateTimeField):
d = value
return 'dt(%d,%d,%d,%d,%d,%d)' % (
d.year, d.month, d.day, d.hour, d.minute, d.second)


It must convert the value to a naive date before writing it to the stream:

if isinstance(field, models.DateTimeField):
if is_aware(value):
d = make_naive(value)
else:
d = value
return 'dt(%d,%d,%d,%d,%d,%d)' % (
d.year, d.month, d.day, d.hour, d.minute, d.second)


I verified my theory with another double dump after pulling above change:

loader.save(create_changes_change(u'1',dt(2015,11,16,6,44,59),...


loader.save(create_changes_change(u'1',dt(2015,11,16,6,44,59),...


So now it looks okay.

I think that I don’t need to automate this test because this is an exceptional situation. But I should probably run it manually again when I’ll do releases on the other production sites.

## Installing linod as a daemon¶

Then I installed linod as daemon. I prepared two bash script templates and updated the docs about The Lino Daemon.

But it turned out that lino.utils.daemoncommand does not collaborte well with newer Django versions.

This remains for tomorrow. It is not that urgent, the only problem until it is done is that notifications won’t be sent out as emails.