srfi/19 reads the locale once then never checks the current language

[euhmeuh]

The srfi/19 module uses locale bundles defined in srfi/29.

But it reads (current-locale) only once at require time, which sets the values of (current-language) and (current-country), then never bothers to read the parameters again.

This means that if you want to display a date in different languages, you're stuck with the language that was set when running the program.

Example of what's wrong:

> (require srfi/19 srfi/29)
> (parameterize ([current-locale "es"]
                 [current-language 'es])
    (date->string (make-date 0 0 0 0 30 3 2018 0) "~A, ~B ~e, ~Y"))

"Friday, March 30, 2018" ;; should be Spanish

> (current-locale "es")
> (require srfi/19 srfi/29)
> (date->string (make-date 0 0 0 0 30 3 2018 0) "~A, ~B ~e, ~Y")

"viernes, Marzo 30, 2018" ;; is Spanish because the locale was set before loading the module

> (parameterize ([current-locale "en"]
                 [current-language 'en])
   (date->string (make-date 0 0 0 0 30 3 2018 0) "~A, ~B ~e, ~Y"))

"viernes, Marzo 30, 2018" ;; should be English but is still Spanish

While SRFI/19 specifies that locales should be handled:

These procedures provide conversion to and from strings. They are required. The specification below describes a 'locale;' the specification of locales is beyond this SRFI.

~A | locale's full weekday name
~B | locale's full month day
...

Expected behavior:

(current-locale) should set the values of (current-language) and (current-country) once.
The locale is not supposed to change during runtime, so reading it once is fine. This is already the case so it's already good.

BUT changing the (current-language) or (current-country) should have an impact on the date formats! Those values are expected to change.

I'm planning to make a pull request with those changes.

• Reading (current-locale) only once to set the default values.
• Reading (current-language) and (current-country) every time localized-template is called.

What do you think about that new behavior?