Translate error messages

Drupal development best practices say we should not translate variable strings. (Except for the '$which' case which I'm handwaving away in a comment...)

Also, the logger should get the untranslated message. (The standard dblog saves the untranslated message plus replacements separately, and translates them on output. We don't want the translation system to retranslate the already translated message.)

How does this work for you? ^ (UserVisibleException having the translated message, but having the untranslated message plus replacements available for e.g. logging.

OK, if this works then I'll commit it and do a new release.

There are a bunch of examples in core of messages being translated, like this one from the block_content module:

Oh, absolutely. Messages should be translated. (At least the "User facing" exceptions.) This was either an oversight or laziness when I committed #3053187: Improve error messages when account doesn't map. Thank you for contributing this.

But we shouldn't pass variable messages, like Destination URL query parameter must not be external: $destination. (A string containing the $while is still 'bad', but not as bad because it has only ~3 permutations. I'll probably get rid of it completely in 4.x, along with the rest of that code block.)

Note also in that commit that the logger message arguments aren't translated, just the arguments to addError().

You're right. I mean the logger should get the template message plus arguments separately, so e.g. Destination URL query parameter must not be external: @destination, with any argument not substituted yet but passed in separately.