[Django] #27359: Make it possible to specify a default template engine
Django
----------------------------------+------------------------------
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Component: Template system | Version: 1.10
Severity: Normal | Keywords: template engines
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------------+------------------------------
This is my first django ticket here. Please, forgive for possible
mistakes.
Issue:
I want to be able to use a custom template engine (same DjangoTemplates,
but with different settings). Multiple template engines seems to be a
great feature, but it becomes not that usable with big projects that
depend on third party packages (such as django-cms, wagtail, etc) - you
have to tell each view/render to use the default engine, otherwise you get
"Several DjangoTemplates backends are configured. You must select one
explicitly." `ImproperlyConfigured` exception.
Solution:
It would be really useful if it would be possible to mark one of the
template engines as default and choose alternative engine where desired.
Changes to :meth:`django.template.engine.get_default` and engine
configuration (`TEMPLATES` setting) would be really trivial. I could make
a patch if approved.
Thank you (in any case)!
--
Ticket URL: <https://code.djangoproject.com/ticket/27359>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Component: Template system | Version: 1.10
Keywords: template engines | Triage Stage: Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Aymeric Augustin):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Comment:
You shouldn't hit this error unless the third party apps rely on
deprecated or private APIs.
Can you provide the full stack trace for the exception you're getting?
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:1>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Component: Template system | Version: 1.10
Keywords: template engines | Triage Stage: Unreviewed
Easy pickings: 0 | UI/UX: 0
Comment (by Artur Barseghyan):
@Aymeric Augustin:
Sure!
---
My settings:
{{{
TEMPLATES = [
# The default engine - a heavy one with a lot of context processors
{
'NAME': 'default',
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [],
'APP_DIRS': True,
'OPTIONS': {
'context_processors': [
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
'django.template.context_processors.i18n',
'django.template.context_processors.request',
'django.template.context_processors.media',
'django.template.context_processors.static',
'sekizai.context_processors.sekizai',
'cms.context_processors.cms_settings',
],
'debug': True,
}
},
# Light engine - only very necessary things go here
{
'NAME': 'light',
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [],
'APP_DIRS': True,
'OPTIONS': {
'context_processors': [
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
'django.template.context_processors.i18n',
'django.template.context_processors.request',
'django.template.context_processors.media',
'django.template.context_processors.static',
],
'debug': True,
},
},
]
}}}
---
{{{
Environment:
Request Method: GET
Request URL: http://localhost:8000/de-at/suchen/
Django Version: 1.8.7
Python Version: 2.7.6
Installed Applications:
('djangocms_admin_style',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.redirects',
'django.contrib.staticfiles',
'django.contrib.sites',
'django.contrib.sitemaps',
'mptt',
'treebeard',
'menus',
'sekizai',
'easy_select2',
'easy_thumbnails',
'metatags',
'ckeditor',
'cmsplugin_filer_file',
'cmsplugin_filer_folder',
'cmsplugin_filer_link',
'cmsplugin_filer_image',
'cmsplugin_filer_teaser',
'cmsplugin_filer_video',
'cms',
'hvad',
'reversion',
'compressor',
'filer',
'rosetta',
'debug_toolbar')
Installed Middleware:
('django.middleware.cache.UpdateCacheMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.contrib.redirects.middleware.RedirectFallbackMiddleware',
'django.middleware.locale.LocaleMiddleware',
'django.contrib.admindocs.middleware.XViewMiddleware',
'django.middleware.common.CommonMiddleware',
'cms.middleware.page.CurrentPageMiddleware',
'cms.middleware.user.CurrentUserMiddleware',
'cms.middleware.toolbar.ToolbarMiddleware',
'cms.middleware.language.LanguageCookieMiddleware',
'django.middleware.cache.FetchFromCacheMiddleware',
'debug_toolbar.middleware.DebugToolbarMiddleware')
Traceback:
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/core/handlers/base.py" in get_response
164. response = response.render()
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/response.py" in render
158. self.content = self.rendered_content
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/response.py" in rendered_content
135. content = template.render(context, self._request)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/backends/django.py" in render
74. return self.template.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
210. return self._render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/test/utils.py" in instrumented_test_render
96. return self.nodelist.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
905. bit = self.render_node(node, context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render_node
919. return node.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/loader_tags.py" in render
135. return compiled_parent._render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/test/utils.py" in instrumented_test_render
96. return self.nodelist.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
905. bit = self.render_node(node, context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render_node
919. return node.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/classytags/core.py" in render
138. return self.render_tag(context, **kwargs)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/sekizai/templatetags/sekizai_tags.py" in render_tag
79. rendered_contents = nodelist.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
905. bit = self.render_node(node, context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render_node
919. return node.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/classytags/core.py" in render
138. return self.render_tag(context, **kwargs)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/sekizai/templatetags/sekizai_tags.py" in render_tag
79. rendered_contents = nodelist.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
905. bit = self.render_node(node, context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render_node
919. return node.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/classytags/core.py" in render
138. return self.render_tag(context, **kwargs)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/templatetags/cms_tags.py" in render_tag
681. rendered_contents = nodelist.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
905. bit = self.render_node(node, context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render_node
919. return node.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/loader_tags.py" in render
65. result = block.nodelist.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render
905. bit = self.render_node(node, context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in render_node
919. return node.render(context)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/classytags/core.py" in render
138. return self.render_tag(context, **kwargs)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/templatetags/cms_tags.py" in render_tag
308. content = get_placeholder_content(context, request,
page, name, inherit, nodelist)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/templatetags/cms_tags.py" in get_placeholder_content
227. placeholder = _get_placeholder(current_page, page, context,
name)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/templatetags/cms_tags.py" in _get_placeholder
191. placeholders = page.rescan_placeholders().values()
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/models/pagemodel.py" in rescan_placeholders
1378. placeholders = get_placeholders(self.get_template())
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/utils/placeholder.py" in get_placeholders
236. placeholders =
_scan_placeholders(_get_nodelist(compiled_template))
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/utils/placeholder.py" in _scan_placeholders
203. placeholders += _extend_nodelist(node)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/utils/placeholder.py" in _extend_nodelist
260. _extend_blocks(extend_node, blocks)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/utils/placeholder.py" in _extend_blocks
288. parent = extend_node.get_parent(get_context())
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/cms/utils/placeholder.py" in get_context
40. context.template = Template('')
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/base.py" in __init__
188. engine = Engine.get_default()
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/utils/lru_cache.py" in wrapper
125. result = user_function(*args, **kwds)
File "/home/me/.virtualenvs/myenv/local/lib/python2.7/site-
packages/django/template/engine.py" in get_default
83. "Several DjangoTemplates backends are configured. "
Exception Type: ImproperlyConfigured at /de-at/suchen/
Exception Value: Several DjangoTemplates backends are configured. You must
select one explicitly.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:2>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Unreviewed
Easy pickings: 0 | UI/UX: 0
Changes (by Artur Barseghyan):
* version: 1.10 => 1.8
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:3>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Unreviewed
Easy pickings: 0 | UI/UX: 0
Comment (by Aymeric Augustin):
Right, this situation is described in this part of the documentation:
https://docs.djangoproject.com/en/1.10/ref/templates/api/#loading-a-template
(the first two paragraphs).
I suppose the transition could be smoothed by adopting a convention for
determining the default Django templates engine, perhaps by deciding it
the one called "django" (or similar) when there are multiple engines
configured.
Can you start by reporting this issue to `django-cms`? They're doing
`context.template = Template('')` which, per the current documentation,
isn't supported.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:4>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Unreviewed
Easy pickings: 0 | UI/UX: 0
Comment (by Artur Barseghyan):
@Aymeric Augustin:
Thanks! I have already tracked it down and reported an issue.
- https://github.com/divio/django-cms/issues/5730
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:5>
Django
Reporter: Artur Barseghyan | Owner: nobody
Component: Template system | Version: 1.8
Keywords: template engines | Triage Stage: Unreviewed
Easy pickings: 0 | UI/UX: 0
Changes (by Tim Graham):
* status: new => closed
* resolution: => needsinfo
Comment:
Feel free to reopen if it turns out some change is needed in Djano after
all.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:6>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Unreviewed
Easy pickings: 0 | UI/UX: 0
Changes (by Raphael Das Gupta):
* status: closed => new
* resolution: needsinfo =>
Comment:
django-crispy-forms [https://github.com/django-crispy-forms/django-crispy-
forms/blob/884a28e08204ef49da8b53fd32a9d19d6de7f393/crispy_forms/layout.py#L400
seems to have the same problem] when used in a Django project that has
multiple template engines of the same backend configured. (I haven't yet
tried with multiple engines of different backends.)
What are libraries supposed to use instead of `Template('template content
here')`? By definition they cannot know what template engines the projects
that the library will be used in have configured.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:7>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Carl Meyer):
* stage: Unreviewed => Accepted
Comment:
Given the current API, we are effectively asking projects like django-cms
or crispy-forms (any third-party project that wants to load and render a
Django template using the project's settings) to require their users to
specify some setting (like `DJANGO_CMS_TEMPLATE_ENGINE`) if the project
has more than one DjangoTemplate engine configured. This may be OK: it's
explicit and gives the project fine-grained control per third-party
project. On the downside, it's unlikely to be the obvious first-choice for
the author of a third-party project; the obvious first choice is to just
try instantiating `Template` directly, and even worse, this will probably
appear to work fine until they think to test (or more likely, one of their
users reports a bug) with multiple configured DTL engines.
IMO currently direct instantiation of `Template` is an attractive nuisance
that appears easy and obvious and only breaks in edge cases, at which
point the person who hits the problem (the project owner) has no
reasonable way to fix it (without forking the third-party project).
I think we must do one of two things. We could a) deprecate and eventually
remove direct instantiation of `Template` altogether, removing the
attractive nuisance and requiring everyone to always be explicit from the
start. Or we could b) add a "default DTL engine" marker, as suggested in
this ticket, so that when a third-party project does the easy and naive
thing (directly instantiate `Template`), a project owner with multiple DTL
engines configured has some recourse to fix it without forking.
I think (b) may be the more practical solution, and kinder to our user
base.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:8>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Simon Charette):
I also think (b) is the most practical solution.
This problem also manifested itself in other project such as
[https://github.com/carltongibson/django-filter/issues/578 django-filter].
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:9>
Django
Reporter: Artur Barseghyan | Owner: nobody
Type: New feature | Status: new
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Carlton Gibson):
As maintainer of both django-filter and crispy forms, I'd say I (too) am
in favour of the `b` solution, i.e. adopting the proposal.
If we were writing new code, requiring an explicit template engine would
be fine, but we're seeing code that's been working fine — quite literally
— for years that's leading to the error here.
What's more it's only (≈) 1 user in a 100 that configures multiple
template engines so the point about it being an untested and surprising
edge-case is exactly right.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:10>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Type: New feature | Status: assigned
Component: Template system | Version: 1.8
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Carlton Gibson):
* status: new => assigned
* owner: nobody => Carlton Gibson
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:11>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Type: New feature | Status: assigned
Component: Template system | Version: 1.8
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Simon Charette):
Another related issue
[https://github.com/nedbat/django_coverage_plugin/pull/21 django-coverage-
plugin] issue.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:12>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Type: New feature | Status: assigned
Component: Template system | Version: 1.8
Severity: Normal | Resolution:
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Carlton Gibson):
* has_patch: 0 => 1
Comment:
[[https://github.com/django/django/pull/8000 PR]
Adds a failing test case for the issue and a naive fix.
Here we just take the first DTL engine returned. Users should employ
collections.OrderedDict if they need to control this prior to Python 3.6.
Need to add a note to the docs to that effect if the patch is
acceptable.
Alternative proposals:
Have a naming convention. e.g. pick engine named 'default'
Add a specific OPTION to the config dict.
This is something of an edge case, and so, (IMO) 'pick the first'
should be sufficient.
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:13>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Type: New feature | Status: assigned
Component: Template system | Version: 1.8
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Raphael Das Gupta):
* needs_better_patch: 0 => 1
Comment:
See https://github.com/django/django/pull/8000#issuecomment-282727217
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:14>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Type: New feature | Status: assigned
Component: Template system | Version: 1.8
Severity: Normal | Resolution:
Keywords: template engines | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Raphael Das Gupta):
* needs_better_patch: 1 => 0
Comment:
Patch
[https://github.com/django/django/pull/8000#pullrequestreview-28069688
looks good now].
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:15>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Type: New feature | Status: assigned
Component: Template system | Version: 1.8
Severity: Normal | Resolution:
| checkin
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Raphael Das Gupta):
* stage: Accepted => Ready for checkin
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:16>
Django
Reporter: Artur Barseghyan | Owner: Carlton
| Gibson
Component: Template system | Version: 1.8
Keywords: template engines | Triage Stage: Ready for
| checkin
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Tim Graham <timograham@…>):
* status: assigned => closed
* resolution: => fixed
Comment:
In [changeset:"6b3724fa1116c0949a6e0cd3e0dd55959a3abd93" 6b3724fa]:
{{{
#!CommitTicketReference repository=""
revision="6b3724fa1116c0949a6e0cd3e0dd55959a3abd93"
Fixed #27359 -- Made Engine.get_default() return the first DjangoTemplates
engine if multiple are defined.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27359#comment:17>