Lualatex : € as a utf8 character is not recognized : why?

Question

I need to include some tex files as parts of a more global project. Some of this global projects have to be compiled with pdflatex, some others with lualatex, but the parts are the same. All this part files are written with a € as an utf8 character. I would like avoid to replace them by a \texteuro.

Is there a way to make lualatex understand € as a \texteuro ?

\documentclass[french]{article}
\RequirePackage{ifluatex}
\ifluatex
    \RequirePackage{fontspec}
    \RequirePackage{luacode}
\else
    \RequirePackage[utf8]{inputenc}
    \RequirePackage[T1]{fontenc}
\fi

\RequirePackage{fourier}

\begin{document}
36\,\texteuro % works with both pdflatex lualatex

36\,€ % doesn't work with lualatex
\end{document}

Answer 1

You can use newunicodechar package and define

\newunicodechar{€}{\texteuro}

Code:

\documentclass{article}
\RequirePackage{ifluatex}
\ifluatex
    \RequirePackage{fontspec}
    \RequirePackage{luacode}
\else
    \RequirePackage[utf8]{inputenc}
    \RequirePackage[T1]{fontenc}
\fi
\let\hbar\hhhbar    %% without this I get a warning
\RequirePackage{fourier}

\usepackage{newunicodechar}
\newunicodechar{€}{\texteuro}

\begin{document}
36\,\texteuro % works with both pdflatex lualatex

36\,€ % doesn't work with lualatex
\end{document}

Then it should work in both pdflatex and lualatex.

Answer 2

With \usepackage{fourier} you are simply ignoring fontspec and using a family of “classical” 256 character font.

You can use classical fonts with LuaLaTeX, without loading fontspec, but luainputenc:

\documentclass{article}
\usepackage{ifluatex}
\usepackage[TS1,T1]{fontenc} % load TS1 so luainputenc will know
\ifluatex
  \usepackage{luacode}
  \usepackage[utf8]{luainputenc}
\else
  \usepackage[utf8]{inputenc}
\fi

\usepackage{fourier}

\begin{document}
36\,\texteuro % works with both pdflatex lualatex

36\,€ % doesn't work with lualatex
\end{document}

Of course this will not use the full strengths of LuaLaTeX as regards to fonts, but it's impossible anyway if you want your document to be processable with LuaLaTeX and pdfLaTeX (and loading luacode doesn't make much sense).

A probably better solution is to use a text font replacement for Utopia, such as the very recent Erewhon font:

\documentclass{article}
\usepackage{ifluatex}
\ifluatex
  \usepackage{luacode}
  \usepackage{fourier}
  \usepackage{fontspec}
  \setmainfont{Erewhon}
\else
  \usepackage[T1]{fontenc}
  \usepackage[utf8]{inputenc}
  \usepackage{fourier}
\fi


\begin{document}
36\,\texteuro % works with both pdflatex lualatex

36\,€ % doesn't work with lualatex

Some math $a+\mathrm{a}=\int_{0}^{1} f(x)\,dx$
\end{document}

Answer 3

As it is already verified, I put also my solution, suggested in comments.

\documentclass{article}
\usepackage{fourier}
\catcode`\€=\active
\def€{\texteuro} 
\begin{document}
36 €
\end{document}