Request for Adding Support for Localized Key References

[zyf722]

Appreciation

First, I want to thank you first for taking on the maintenance of the original python-i18n package and add more functionality to it.
This simple, lightweight, and user-friendly i18n tool saves me a lot of time. Salute.

Feature Request

Here I'd like to request a feature addition to enhance the package's capabilities. Specifically, the support for localized key references.

An example written in JSON is provided as follows:

{
    "en": {
        "DUMMY_1": "dummy1",
        "DUMMY_2": "dummy2",
        "MENU_A_DUMMY": "${DUMMY_1} and ${DUMMY_2}",
        "MENU_B_DUMMY": "${DUMMY_1}"
    }
}

And the corresponding expected result will be:

i18n.t("MENU_A_DUMMY") # Output: dummy1 and dummy2

With a special syntax (${} here, could be replaced with any other delimiters), it would be possible to reference existing localized keys within other translations.

The proposed approach offers two significant advantages: interface flexibility through referencing multiple localized keys within a single translation, allowing diverse interfaces that are easily modifiable in the future, and translation reusability, minimizing redundancy and improving maintenance efficiency.

I believe adding support for localized key references would improve the package's utility, especially for projects with complex translation requirements.

Thank you for considering this enhancement request.

[zyf722]

I have created a simple wrapper class to address this issue.

import i18n
from string import Template

i18n.set('file_format', 'json')
i18n.set('filename_format', '{locale}.{format}')
i18n.load_path.append('./i18n/')

class KeyRefFormatter(Template):
    delimiter = "$"
    
    def __init__(self, template, **kwargs):
        template = i18n.t(template, **kwargs)
        super().__init__(template)
        self.kwargs = kwargs
    
    # From https://github.com/python/cpython/issues/90465
    # For Python 3.11+, use library method string.Template.get_identifiers() instead
    def get_identifiers(self):
        return list(
            set(
                filter(
                    lambda v: v is not None,
                    (mo.group('named') or mo.group('braced') 
                     for mo in self.pattern.finditer(self.template))
                )
            )
        )
        
    def format(self):
        sub_dict = { key: i18n.t(key, **self.kwargs) for key in self.get_identifiers() }
        return self.safe_substitute(sub_dict)

def _(key, **kwargs):
    return KeyRefFormatter(key, **kwargs).format()

print(_('MENU_A_DUMMY', placeholder_1="def", placeholder_2="abc"))
# Output: dummy1 with def, and dummy2 with abc

The corresponding en.json file is as follows:

{
    "en": {
        "DUMMY_1": "dummy1 with %{placeholder_1}",
        "DUMMY_2": "dummy2",
        "MENU_A_DUMMY": "${DUMMY_1}, and ${DUMMY_2} with %{placeholder_2}",
        "MENU_B_DUMMY": "${DUMMY_1}"
    }
}

This is a workaround and a temporary solution. Perhaps it can be further integrated into this project in the future?

[solaluset]

Thanks for opening the issue. I agree that this can be a useful feature.

[solaluset]

You can take a look at my pull request and share your thoughts.

[zyf722]

Looks good and thanks for your work!

Let me confirm, so the static reference feature and placeholder feature share the delimiter %, right?

Additionally, could you explain the behavior of the feature when the referenced value contains a placeholder?

For instance, in my example above, MENU_A_DUMMY includes the placeholder %{placeholder_2} and also references DUMMY_1, which itself contains the placeholder %{placeholder_1}. In this case, would i18n.t('MENU_A_DUMMY', placeholder_1="def", placeholder_2="abc") work as expected? Perhaps this could be added as a test case.

[solaluset]

It's already covered by tests and described in the readme. You probably got confused because the library uses placeholder delimiter (defaults to %) for placeholders (and now static refs) and namespace delimiter (defaults to .) for keys.

To create a static reference, you put it as key prefixed with namespace delimiter ("%{.DUMMY_1}, and %{.DUMMY_2} with %{placeholder_2}" in your case)

Let me know if you have any suggestions for description improvement, because I'm kind of bad when it comes to explaining things ;)

[zyf722]

Oh, I figure it out now. It would be great if everything works just as expected! 👏
The description is just fine and thank you for the update. Looking forward to the new version being released on PyPI!

[solaluset]

I'll keep this open until the new release is published

[solaluset]

New version is released 🎉
Thanks for your input. In case if something doesn't work as intended, please open a new issue