.htaccess: Remove extension and force traling slash (seo friendly) - apache

Question

I've been playing about with my .htaccess file and so far that's doesn't work.
I'm trying to force the .www prefix, while removing the .html extension and adding/force a trailing slash at the end of URL.
Example (with test.html file):
http://www.domain.com/test.html
http://www.domain.com/test
http://domain.com/test.html
http://domain.com/test
= http://www.domain.com/test/
My .htaccess:
Options +FollowSymLinks +MultiViews
RewriteEngine on
Rewritecond %{HTTP_HOST} ^laforgenumerique.fr$
Rewriterule ^(.*) http://www.laforgenumerique.fr/$1 [QSA,L,R=301]
#REMOVE DOT HTML
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ $1.html [L]
#FORCE TRAILING SLASH
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^[^/]+$ %{REQUEST_URI}/ [L,R=301]
#CUSTOM ERROR DOCUMENT
ErrorDocument 400 http://www.laforgenumerique.fr/404.html
ErrorDocument 401 http://www.laforgenumerique.fr/404.html
ErrorDocument 403 http://www.laforgenumerique.fr/404.html
ErrorDocument 404 http://www.laforgenumerique.fr/404.html
ErrorDocument 500 http://www.laforgenumerique.fr/404.html
Please help!
Host: OVH

Answer 1

You wrote:
#REMOVE DOT HTML
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ $1.html [L]
#FORCE TRAILING SLASH
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^[^/]+$ %{REQUEST_URI}/ [L,R=301]
It seems that you are trying to mix two separate rules.
[L] suffix means that this is the last rule; all rules below will be skipped even if they are suitable.
You may try something like this:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ www.$1
RewriteRule ^(.*).html$ $1/ [L]