htaccess trailing slashes just for one URL - apache

Question

Having the following .htaccess rules
<IfModule mod_rewrite.c>
<IfModule mod_negotiation.c>
Options -MultiViews -Indexes
</IfModule>
RewriteEngine On
RewriteRule ^dashboard/(.*)$ back/index.html [L]
# Handle Authorization Header
RewriteCond %{HTTP:Authorization} .
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} (.+)/$
RewriteRule ^ %1 [L,R=301]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]
</IfModule>
I want to redirect all incomings requests if they match /dashboard to end with a trailing slash. But only for this case.
if I use
RewriteRule ^dashboard/(.*)$ back/index.html [L]
RewriteCond %{REQUEST_URI}dashboard /+[^\.]+$
RewriteRule ^(.+[^/])$ %{REQUEST_URI}/ [R=301,L]
will fail because all my URL's are becoming a trailing slash.
How can I have a trailing slash only for this case?

Answer 1

Have it this way:
<IfModule mod_rewrite.c>
<IfModule mod_negotiation.c>
Options -MultiViews -Indexes
</IfModule>
RewriteEngine On
RewriteRule ^dashboard/(.*)$ back/index.html [L]
# Handle Authorization Header
RewriteCond %{HTTP:Authorization} .
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
# add / after /dashboard
RewriteRule ^dashboard$ $0/ [L,R=301,NC]
# remove / from all other URIs
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} (.+)/$
RewriteRule !^dashboard/ %1 [L,R=301,NC]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]
</IfModule>
Make sure to test it after completely clearing browser cache.