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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
benefits/core/models
transit.py
benefits/eligibility
views.py
benefits/eligibility/context
__init__.py
agency.py
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Annoying issue with % characters in copy

Some reminders:

• makemessages scans our code and templates for translatable strings and generates PO files
• compilemessages reads the PO files and compiles them into binary MO files which are used when the app runs

makemessages is called when we run the helper ./bin/makemessages.sh script.
compilemessages is called whenever the ./bin/init.sh script is run, which would be either when you run ./bin/reset_db.sh or when the app container starts.

Background

Before this PR, our copy containing % characters works fine.

In our templates we have the translatable string, e.g.:

# eligibility/index--cst.html
...

{% translate "Cal-ITP doesn’t save any of your information. All CST transit benefits reduce fares by 50% for bus service on fixed routes." %}

...

When the makemessages command generates a PO entry for this string, it marks the entry as #, python-format (because % in Python is the old-style string-formatting operator). It also realizes this % is not actually being used for interpolation, so it escapes the % character, which is done by putting another % in front. This results in the following PO entry (notice the %%):

#, python-format
msgid ""
"Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50%% for bus service on fixed routes."
msgstr ""

Then, in the Spanish translation, we also use %%.

#, python-format
msgid ""
"Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50%% for bus service on fixed routes."
msgstr ""
"Cal-ITP no almacena su información. Todos los beneficios de tránsito de CST "
"reducen las tarifas de autobuses en un 50%%."

compilemessages is able to compile the PO files, and the copy is correct when the template is rendered:

Moving the translatable string to Python code

With our context approach, we need to move the string from the template into Python code, e.g.:

...

eligibility_index = {
AgencySlug.CST.value: EligibilityIndex(form_text=_("Cal-ITP doesn’t save any of your information. All CST transit benefits reduce fares by 50%% for bus service on fixed routes."))
...
}

...

Notice we use an escaped percent sign (%%).

makemessages sees this and generates the same PO entries as before. compilemessages is able to compile the PO files.

But the copy is not correct when the template is rendered. It shows %%.

Why?? If you think about the template's perspective, the difference from before is that the string to be translated now has %% in it. So we need to somehow get it to have just % instead.

Failed attempts to solve the issue

Use one % in the translatable string (506f241)

We modify the translatable string to only use one % character:

...

eligibility_index = {
AgencySlug.CST.value: EligibilityIndex(form_text=_("Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50% for bus service on fixed routes."))
...
}

...

makemessages is able to generate a PO entry with just one % character:

#, python-format
msgid ""
"Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50% for bus service on fixed routes."
msgstr ""

and we update the Spanish entry to also use one % character:

#, python-format
msgid ""
"Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50% for bus service on fixed routes."
msgstr ""
"Cal-ITP no almacena su información. Todos los beneficios de tránsito de CST "
"reducen las tarifas de autobuses en un 50%."

However, then compilemessages raises an error. Because the entry is marked as #, python-format, compilemessages checks the string and sees that it is not a valid Python string (the % character is not doing interpolation nor is it escaped).

Execution of msgfmt failed: /home/runner/work/benefits/benefits/benefits/locale/es/LC_MESSAGES/django.po:47: 'msgstr' is not a valid Python format string, unlike 'msgid'. Reason: The string ends in the middle of a directive.
/home/runner/work/benefits/benefits/benefits/locale/es/LC_MESSAGES/django.po:55: 'msgstr' is not a valid Python format string, unlike 'msgid'. Reason: The string ends in the middle of a directive.
/home/runner/work/benefits/benefits/benefits/locale/es/LC_MESSAGES/django.po:63: 'msgstr' is not a valid Python format string, unlike 'msgid'. Reason: The string ends in the middle of a directive.
/home/runner/work/benefits/benefits/benefits/locale/es/LC_MESSAGES/django.po:71: 'msgstr' is not a valid Python format string, unlike 'msgid'. Reason: In the directive number 1, the character 'p' is not a valid conversion specifier.
/home/runner/work/benefits/benefits/benefits/locale/es/LC_MESSAGES/django.po:92: number of format specifications in 'msgid' and 'msgstr' does not match
msgfmt: found 5 fatal errors
CommandError: compilemessages generated one or more errors.

(see this failed init in pytest action)

Remove #, python-format from the generated PO files (1a1c26a)

Building off the above failed attempt, we manually remove #, python-format from these Eligibility Index PO entries.

This works:

However, when we inevitably run makemessages again, it'll just put back those #, python-format, so this is not a sustainable solution.

(see corresponding failed makemessages check in GitHub Action)

Solution

The Django docs tell us that if your translatable string is coming from a variable or is computed, then makemessages will not see it. It only sees the literal strings that are passed into some gettext function call.

We can take advantage of this to solve our problem.

In our Python code, we call .replace("%%", "%") on the literal string:

...

eligibility_index = {
AgencySlug.CST.value: EligibilityIndex(form_text=_("Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50%% for bus service on fixed routes.".replace("%%", "%")))
...
}

...

makemessages will see the literal string and generate a valid Python string with %%:

#, python-format
msgid ""
"Cal-ITP doesn’t save any of your information. All CST transit benefits "
"reduce fares by 50%% for bus service on fixed routes."
msgstr ""

compilemessages is able to compile the PO files.

The template is given the string that now has just one %, and the copy is correct:

I'll need to rebase on top of changes from #2714 and add a test to check eligibility_index contains all AgencySlugs.