Replace normal spaces with non-breaking spaces before french punctuation marks

In french, we use to have spaces before some punctuation marks like !?;: but of course they should never go to the next line. Ideally editors should put a nbsp themselves but most of the time they just put a normal space. I thought Typogrify (or Smartypants?) would do the automatic conversion, but it happens that it doesn't. And I did not find any module to do that, which sometimes results in ugly things in french text.
I might try to make some patch myself, but I wanted to know if the actual behavior (do nothing) is by design, or something like that.
Any thought?