French

To typeset French documents it’s strongly advisable using the default style by Daniel Flipo. It’s very complete and customizable, and works very well with pdflatex, lualatex and xelatex, although the last two, ie, the Unicode engines, handle much better the spacing.

Please, refer to its detailed manual for further info, available here.

Locale files

Alternatively, and mainly as a secondary language, you can resort to the ini locale files, loaded with \babelprovide (or with some of the provide options). Here is an example, which works with lualatex:

\documentclass{article}

\usepackage[spanish]{babel}
\babelprovide[
  transforms = punctuation.space
]{french}

\begin{document}

Español. \foreignlanguage{french}{Je dis: «Et voilà!»}. Español.

\end{document}

With xelatex, instead of a transform, use a ‘interchar’. Note this feature requires import:

  interchar = punctuation.space, import

You can use both keys, if you like, in documents to be typeset with either lualatex or xetex.