Internationalizing strings in extensions

mark its strings for internationalization

Internationalizing strings in extensions¶

See also
In order to internationalize your extension you must mark its strings
for internationalization. See also
Translating CKAN.
This tutorial assumes that you have read the Writing extensions tutorial.

We will create a simple extension to demonstrate the translation of strings
inside extensions. After running:
paster --plugin=ckan create -t ckanext ckanext-itranslation

Change the plugin.py file to:
# encoding: utf-8

from ckan import plugins
from ckan.plugins import toolkit

class ExampleITranslationPlugin(plugins.SingletonPlugin):
    plugins.implements(plugins.IConfigurer)

    def update_config(self, config):
        toolkit.add_template_directory(config, 'templates')

Add a template file ckanext-itranslation/templates/home/index.html
containing:
{% ckan_extends %}

{% block primary_content %}
{% trans %}This is an untranslated string{% endtrans %}
{% endblock %}

This template provides a sample string that we will internationalize in this
tutorial.

Note
While this tutorial only covers Python/Jinja templates it is also possible
(since CKAN 2.7) to translate strings in an extension’s JavaScript
modules.

Extract strings¶

Tip
If you have generated a new extension whilst following this tutorial the
default template will have generated these files for you and you can simply
run the extract_messages command immediately.

Check your setup.py file in your extension for the following lines
setup(
    entry_points='''
        [ckan.plugins]
        itranslation=ckanext.itranslation.plugin:ExampleITranslationPlugin
        [babel.extractors]
        ckan = ckan.lib.extract:extract_ckan
    '''

    message_extractors={
        'ckanext': [
            ('**.py', 'python', None),
            ('**.js', 'javascript', None),
            ('**/templates/**.html', 'ckan', None),
        ],
    }

These lines will already be present in our example, but if you are adding
internationalization to an older extension, you may need to add them.
If you have your templates in a directory differing from the default location
(ckanext/yourplugin/i18n),
you may need to change the message_extractors stanza. You can read more
about message extractors in the babel documentation.
Add a directory to store your translations:
mkdir ckanext-itranslations/ckanext/itranslations/i18n

Next you will need a babel config file. Add a setup.cfg file containing the
following (make sure you replace itranslations with the name of your extension):
[extract_messages]
keywords = translate isPlural
add_comments = TRANSLATORS:
output_file = ckanext/itranslation/i18n/ckanext-itranslation.pot
width = 80

[init_catalog]
domain = ckanext-itranslation
input_file = ckanext/itranslation/i18n/ckanext-itranslation.pot
output_dir = ckanext/itranslation/i18n

[update_catalog]
domain = ckanext-itranslation
input_file = ckanext/itranslation/i18n/ckanext-itranslation.pot
output_dir = ckanext/itranslation/i18n

[compile_catalog]
domain = ckanext-itranslation
directory = ckanext/itranslation/i18n
statistics = true

This file tells babel where the translation files are stored.
You can then run the extract_messages command to extract the strings from
your extension:
python setup.py extract_messages

This will create a template PO file named
ckanext/itranslations/i18n/ckanext-itranslation.pot.
At this point, you can either upload and manage your translations using
Transifex or manually edit your translations.

Manually create translations¶
We will create translation files for the fr locale. Create the translation
PO files for the locale that you are translating for by running init_catalog:
python setup.py init_catalog -l fr

This will generate a file called i18n/fr/LC_MESSAGES/ckanext-itranslation.po.
This file should contain the untranslated string on our template. You can manually add
a translation for it by editing the msgstr section:
msgid "This is an untranslated string"
msgstr "This is a itranslated string"

Translations with Transifex¶
Once you have created your translations, you can manage them using Transifex.
This is out side of the scope of this tutorial, but the Transifex documentation
provides tutorials on how to
upload translations
and how to manage them using the
command line client.

Compiling the catalog¶
Once the translation files (po) have been updated, either manually or via Transifex, compile them
by running:
python setup.py compile_catalog

This will generate a mo file containing your translations that can be used by CKAN.

The ITranslation interface¶
Once you have created the translated strings, you will need to inform CKAN that
your extension is translated by implementing the ITranslation interface in
your extension. Edit your plugin.py to contain the following.
# encoding: utf-8

from ckan import plugins
from ckan.plugins import toolkit
from ckan.lib.plugins import DefaultTranslation

class ExampleITranslationPlugin(plugins.SingletonPlugin, DefaultTranslation):
    plugins.implements(plugins.ITranslation)
    plugins.implements(plugins.IConfigurer)

    def update_config(self, config):
        toolkit.add_template_directory(config, 'templates')

You’re done! To test your translated extension, make sure you add the extension to
your /etc/ckan/default/development.ini, run a paster serve command and browse to
http://localhost:5000. You should find that switching to the fr locale in
the web interface will change the home page string to this is an itranslated
string.

Advanced ITranslation usage¶
If you are translating a CKAN extension that already exists, or you have
structured your extension differently from the default layout. You may have to
tell CKAN where to locate your translated files, you can do this by not having
your plugin inherit from the DefaultTranslation class and instead
implement the ITranslation interface yourself.

i18n_directory()
Change the directory of the .mo translation files

i18n_locales()
Change the list of locales that this plugin handles

i18n_domain()
Change the gettext domain handled by this plugin