Context

When using the translation:update command to generate a translation file, the translated strings are just the original strings with the __ prefix (e.g. original Contact us, "translation": __Contact us). This value can be changed with the --prefix option.

Problem

When generating the translation file for the original language, I want to use an empty prefix. It seems impossible to do that because of the way Symfony Console options work:

$ ./bin/console translation:update en --dump-messages
# translation prefix = '__';

$ ./bin/console translation:update en --dump-messages --prefix=""
# translation prefix = '__';   <-- ERROR: I expected here an empty prefix

$ ./bin/console translation:update en --dump-messages --prefix=" "
# translation prefix = ' ';

$ ./bin/console translation:update en --dump-messages --prefix="aaa"
# translation prefix = 'aaa';

I think in the past we had some issues reported for the way console options work, but I can't find the issues. Considering that setting an option with an empty value is the same as not setting that option looks confusing and it could even be considered a bug.