I'd like to merge the current patch that removes the trailing newline in
the attrs.html template, then revisit the issue of {% include %} stripping
the trailing newline for the next version of Django so we don't need to
rush a decision about that.
On Thursday, January 5, 2017 at 10:05:30 AM UTC-5, Alasdair Nicol wrote:
>
> Would adding the future include tag to the builtins in the template
> OPTIONS work? If it did, then you'd only have to make the change to the
> TEMPLATES setting instead of every template.
>
> OPTIONS={
> 'builtins': ['django.template.future_include'], # put new include
> in it's own module so that we don't add anything else in future.
> }
>
> I'm not familiar with that code, so I don't know whether that would
> override the old include tag.
>
> Cheers,
> Alasdair
>
> On Thursday, 5 January 2017 14:49:58 UTC, Tim Graham wrote:
>>
>> Hi Simon, I mentioned that idea offhand in an earlier mail, however, I
>> feel that it would be really disruptive to force all projects to go through
>> that deprecation and require adding {% load include from future %} to every
>> template that uses the tag to silence warnings (and then remove those lines
>> sometime after the deprecation ends). (More disruptive than just making a
>> backwards-incompatible change that's likely to affect a (hopefully small)
>> subset of users.) I guess I'm open to it if others think that's the way to
>> go though.
>>
>> On Thursday, January 5, 2017 at 9:20:36 AM UTC-5, charettes wrote:
>>>
>>> Hey Tim,
>>>
>>> I just wanted to mention that another approach for a transition plan
>>> could be
>>> to use {% load include from future %} like we did with the {% url %} tag.
>>>
>>> That doesn't answer the question of whether or not we should make the
>>> change
>>> but I think it offers a better upgrade path than a global template
>>> option or
>>> a keep_trailing_newline kwarg.
>>>
>>> Simon
>>>
>>> Le mercredi 4 janvier 2017 14:58:42 UTC-5, Tim Graham a écrit :
>>>>
>>>> Shortly after template widget rendering was merged, an issue about
>>>> extra newlines appearing in the rendered output was reported [0]:
>>>>
>>>> For example, from django-money:
>>>>
>>>> <option value="XFU" \n>UIC-Franc</option>
>>>> \n\n
>>>> <option value="USD" selected\n>US Dollar</option>
>>>> \n\n
>>>>
>>>> The newlines aren't useful and they break assertions like this:
>>>>
>>>> <option value="USD" selected>US Dollar</option> in form.as_p
>>>>
>>>> --- end report---
>>>>
>>>> The reporter suggested removing the trailing newline in the attrs.html
>>>> template but Adam Johnson reported: "POSIX states that all text files
>>>> should end with a newline, and some tools break when operating on text
>>>> files missing the final newline. That's why git has the warning \ No
>>>> newline at end of file and Github has a warning symbol for the missing
>>>> newline."
>>>>
>>>> I suggested that perhaps {% include %} could do .rstrip('\n') on
>>>> whatever it renders.
>>>>
>>>> Preston pointed out that Jinja2 does something similar:
>>>>
>>>> http://jinja.pocoo.org/docs/dev/templates/#whitespace-control
>>>>
>>>> - a single trailing newline is stripped if present
>>>> - other whitespace (spaces, tabs, newlines etc.) is returned
>>>> unchanged
>>>>
>>>> I noted that the issue of {% include %} adding extra newlines was
>>>> raised in #9198 [1] but Malcolm said, "For backwards compatibility reasons
>>>> we cannot change the default behaviour now (there will be templates that
>>>> rely on the newline being inserted)." I was skeptical this would be a
>>>> burdensome change.
>>>>
>>>> Carl replied: "It seems quite likely to me that there are templates in
>>>> the wild relying on preservation of the final newline. People render
>>>> preformatted text (e.g. text emails) using DTL. I probably have some text
>>>> email templates in older projects myself that would break with that
>>>> change.
>>>>
>>>> We could add a new option to {% include %}, though." Adam also said,
>>>> "I too have used DTL for text emails that would break under that
>>>> behaviour.
>>>> New option to include sounds good to me."
>>>>
>>>>
>>>> Me again: In the long run, having {% include %} remove the trailing
>>>> newline seems like a more sensible default. For example, I wouldn't expect
>>>> this code to have a newline inserted between it:
>>>>
>>>>
>>>> {% include "foo.txt" %}
>>>> {% include "bar.txt" %}
>>>>
>>>>
>>>> An option for {% include %} seems superfluous given that if you were
>>>> writing
>>>>
>>>>
>>>> {% include "foo.txt" %}{% include "bar.txt" %}
>>>>
>>>>
>>>> now you can write the first thing which is much more intuitive.
>>>>
>>>>
>>>> How about a keep_trailing_newline TEMPLATES option for backwards
>>>> compatibility for those who don't want to adapt their templates for the
>>>> new
>>>> behavior? Jinja2 has that option.
>>>>
>>>> Carl replied: An engine option may be better than an option to {%
>>>> include %}, though it doesn't allow us to ensure that we strip the
>>>> newline in the specific case of attrs.
>>>>
>>>> How we default the engine option I guess just depends on how seriously
>>>> we take backwards compatibility. If we default it to strip and make people
>>>> add the config to preserve the old behavior, that's not really backwards
>>>> compatible. Historically (as seen in Malcolm's comment) we would choose to
>>>> err on the side of actual backwards compatibility in a case like this,
>>>> even
>>>> if it didn't result in the ideal future behavior. But the adaptation isn't
>>>> hard in this case, so I won't object if the choice is to break back-compat.
>>>>
>>>>
>>>> If it's not a per-include choice, of course, we have to break overall
>>>> back-compat to preserve form-attr-rendering back-compat.
>>>> ----
>>>>
>>>> What do you think?
>>>>
>>>> [0] https://github.com/django/django/pull/7769
>>>> [1] https://code.djangoproject.com/ticket/9198
>>>>
>>>
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