Location of the Jinja Environment directory

PhilippVWC · March 2, 2019, 6:42pm

Hi,

the Jinja Template engine always requires an environment to draw the templates from. Thus an exemplified python module, whose purpose is rendering templates would start like this:

 from Jinja2 import Environment, FileSystemLoader
 env = Environment( loader = FileSystemLoader('templates') )
 myTemplate = env.get_template('template1.html')
 print(myTemplate.render()) ...

Here the FileSystemLoader loads a directory ‘templates’ relative to the location of the calling module. So I would deposit every html template (like template1.html, template2.html) into that directory. So this directory forms a crucial part of the Jinja environment.

If I would now import a Jinja Macro from template1.html into template2.html the import statement knows, where to find template1.html, since the FileSystemLoader defined the location. Namely ‘templates’. So template2.html would start with:
{% from template1.html import macro1 %}, where macro1 is a Jinja Macro defined in template1.html.

So now, I want to know, where this directory is located within the Indico project. I see that many templates, that import macros refer to indico/indico/web/templates, but some Modules like, e.g. groups ( in indico/indico/modules) contain html templates refering to the module groups, like e.g. /indico/indico/modules/groups/templates/groupd_details.html

Cheers,

Philipp

ThiefMaster · March 2, 2019, 7:17pm

Hi, please explain what you are trying to do and we can give you some tips. We use some custom logic to avoid duplicating e.g. module names inside the module(blueprint)-specific template folders.

PhilippVWC · March 2, 2019, 7:36pm

Hi ThiefMaster,

it is a question of general interest. I am learning Jinja at the moment in order to better understand the templating infrastructure of Indico. I recognized today, that Indico templates make heavy use of macros. As far as I know, a macro is imported like e.g. in
indico/indico/modules/events/management/templates/clone_event.html:

{% from 'message_box.html' import message_box %}, where message_box.html contains the macro message_box.

Now I want to know from where Jinja knows, where the template message_box.html is located.

ThiefMaster · March 2, 2019, 10:41pm

The default template folder indico/web/templates/ is set here:

github.com

indico/indico/blob/master/indico/web/flask/app.py#L340


# If you are reading this code and wonder how to access the app:
# >>> from flask import current_app as app
# This only works while inside an application context but you really shouldn't have any
# reason to access it outside this method without being inside an application context.
# When set_path is enabled, SERVER_NAME and APPLICATION_ROOT are set according to BASE_URL
# so URLs can be generated without an app context, e.g. in the indico shell


if _app_ctx_stack.top:
    Logger.get('flask').warn('make_app called within app context, using existing app')
    return _app_ctx_stack.top.app
app = IndicoFlask('indico', static_folder=None, template_folder='web/templates')
app.config['TESTING'] = testing
app.config['INDICO'] = load_config(only_defaults=testing, override=config_override)
configure_app(app, set_path)


with app.app_context():
    if not testing:
        Logger.init(app)
    celery.init_app(app)
    babel.init_app(app)
    multipass.init_app(app)

All the modules have their own blueprint, e.g. here:

github.com

indico/indico/blob/master/indico/modules/announcement/blueprint.py#L23


#
# You should have received a copy of the GNU General Public License
# along with Indico; if not, see <http://www.gnu.org/licenses/>.


from __future__ import unicode_literals


from indico.modules.announcement.controllers import RHAnnouncement
from indico.web.flask.wrappers import IndicoBlueprint




_bp = IndicoBlueprint('announcement', __name__, template_folder='templates', virtual_template_folder='announcement')


_bp.add_url_rule('/admin/announcement', 'manage', RHAnnouncement, methods=('GET', 'POST'))

By default, the template folder that belongs to the blueprint would have priority over core templates, and share the same namespace (this is a design decision in Flask that some people like and some don’t). However, in our case it’s not convenient and usually we’d have to put the templates for that blueprint inside templates/announcement/whatever if we wanted to render them as 'announcement/whatever'. But repeating the module name inside the template folder is somewhat dumb, so I added some code that adds a virtual prefix for all templates in the blueprint’s template folder:

github.com

indico/indico/blob/master/indico/web/flask/wrappers.py#L206-L230


class IndicoFileSystemLoader(FileSystemLoader):
"""FileSystemLoader that makes namespacing easier.


The `virtual_path` kwarg lets you specify a path segment that's
handled as if all templates inside the loader's `searchpath` were
actually inside ``searchpath/virtual_path``.  That way you don't
have to create subdirectories in your template folder.
"""


def __init__(self, searchpath, encoding='utf-8', virtual_path=None):
    super(IndicoFileSystemLoader, self).__init__(searchpath, encoding)
    self.virtual_path = virtual_path


def list_templates(self):
    templates = super(IndicoFileSystemLoader, self).list_templates()
    if self.virtual_path:
        templates = [os.path.join(self.virtual_path, t) for t in templates]
    return templates


def get_source(self, environment, template):

This file has been truncated. show original

PhilippVWC · March 5, 2019, 11:43am

Hi Thiefmaster,

that was very clarifying. Thank you for your detailed response.
Cheers,

Philipp