Thursday, July 21, 2016

I made a release in CPAS de Châtelet, and since today they are not working in Belgium, I had time to explore some problems I encountered more deeply than usual.

Scheduling background tasks and installing Supervisor

It was my second or third Supervisor on a production server, and I am really satisfied with the combination Schedule and Supervisor. Now I updated the docs about The Lino Daemon with django-channels, an extension to the notification framework. Later I also added a page linod: asynchronous Lino daemon, optimized the API and reported #1069.

Configure logging

It seems that messages logged to the console logger are not shown when working through a terminal on a remote server.

I wrote a little script (and added it to lino_book/projects/polly) so you can easily try yourself:

from lino.api import dd"pinglog via")
import logging
logging.getLogger('django').info("pinglog to logger django")
logging.getLogger('lino').info("pinglog to logger lino")
logging.getLogger('').info("pinglog to logger")
logging.getLogger('foo.lino').info("pinglog to logger foo.lino")

Here is the output on my machine:

$ python run
Started run (using lino_book.projects.polly.settings.demo) --> PID 6764
pinglog via
pinglog to logger django
pinglog to logger lino
pinglog to logger
Done run (PID 6764)

As expected, the last message does not get logged, all others do.

When I run the same command in a terminal on a remote server, then I see no output, although all except the last message get correctly logged to the system.log file.

I started a new documentation page About logging. I introduced a new (optional) environment variable LINO_LOGLEVEL.

Odd behaviour of DurationField with default

When restoring the dump, I got this error message:

- esf.ClientSummary {u'esf50': [u'This field cannot be null.'],
  u'esf60': [u'This field cannot be null.'], u'esf70': [u'This
  field cannot be null.']} (170 object(s) with primary key 1, 2,
  183, 184, 185, 186, 187, 188, 189)

This is strange, because I don’t want them to be nullable, and they all have default=Duration("0:00") specified, so why do they now contain None?

Yes, lino_welfare.modlib.esf.models.ClientSummary is indeed the first model ever which uses a DurationField with a default value.

I started to search for bugs in the application logic in lino.modlib.summaries and lino_welfare.modlib.esf.

I then saw that dump2py did not write the “0:00” values correctly. Here is what it generates for every record:,None,2012,None,0,0,0,3,0,0,0,0,0,None,None,None,116,None,False,False,False,None,u''))

And here is a code snippet to verify the problem:

>>> from lino import startup
>>> startup('lino_welfare.projects.chatelet.settings.demo')
>>> from lino.api.doctest import *
>>> ClientSummary = rt.models.esf.ClientSummary
>>> obj = ClientSummary.objects.all()[0]
>>> results = ClientSummary._meta.get_field('results')
>>> print(obj.master)
AUSDEMWALD Alfons (116)
>>> print(obj.esf50)  # AFTER BUGFIX: 0:00
>>> fld = ClientSummary._meta.get_field('esf50')
>>> fld.__class__
<class 'lino.core.fields.DurationField'>
>>> print(fld.value_from_object(obj))  # AFTER BUGFIX: 0:00
>>> print(fld.get_default())
>>> obj.full_clean()    # AFTER BUGFIX no traceback
Traceback (most recent call last):
ValidationError: {u'esf50': [u'Ce champ ne peut pas \xeatre vide.'], u'esf60': [u'Ce champ ne peut pas \xeatre vide.'], u'esf70': [u'Ce champ ne peut pas \xeatre vide.']}
>>> from lino.utils.html2text import html2text
>>> from import Command
>>> # ses = rt.login()
>>> # print(html2text(tostring(results.value_from_object(obj, ses))))
>>> cmd = Command()
>>> print(cmd.value2string(obj, fld))    # AFTER BUGFIX '0:00'
>>> from lino.utils.quantities import Duration
>>> print(Duration("0:00"))

Note that above snippet no longer passes now since the bug is fixed. I used doctest in lieu of a debugger as follows:

$ python -m doctest docs/blog/2016/0721.rst

The problem was in lino.core.fields.DurationField.from_db_value():

def from_db_value(self, value, expression, connection, context):
    return Duration(value) if value else None

This must be:

def from_db_value(self, value, expression, connection, context):
    return Duration(value) if value else self.get_default()

Two other field definitions had their own implementation of from_db_value(), I adapted them as well.

As a result of all this we have one bug less in Lino:

  • Until now Lino did not support well the case of defining a default value for fields of type QuantityField, DurationField or IncompleteDateField. Changed API for these fields: when blank is True, then null must be True as well. The statement “QuantityFields are implemented as CharFields and therefore should not be declared null=True. But if blank=True, empty strings are converted to None values.” is now obsolete.

Failing builds on

Builds on for The lino package, Lino Welfare and others failed because html5lib refused to install with earlier versions:

html5lib requires setuptools version 18.5 or above; please upgrade before installing (you have 0.9.8)

We had that on Travis before. I added a line pip install -U setuptools to the settings of these project.

Rendering “normal html” inside an ExtJS panel

Here is another topic. #1067. We might need this for converting to ExtJS6. Hamza and I have been looking at a layout problem which I suspect to be related to the htmlText CSS class defined in lino.css.

In Lino we often have fragments of custom HTML content (generated by application code) which we want to display in some ExtJS panel.

  • get_slave_summary methods

  • Fields defined using dd.virtualfield, especially dd.HtmlBox

  • Fields defined using dd.displayfield

  • Fields defined using dd.constant

  • The message of a response to some action.

Application code on these places currently does something like:

return E.div(*body, class_='htmlText')


return u"""<div class="htmlText">{0}</div>""".format(html)

Both methods are being used. E.div is preferred in general, except when rendering chunks of HTML coming from a RichTextField or from a template (because in these cases it makes no sense to parse this HTML just to wrap it into an ElementTree which anyway will just be rendered as a string.

New functions ar.html_text and rt.html_text, and lino.modlib.extjs.ext_renderer.ExtRenderer.html_text().