WSGI .htaccess with addon domain - .htaccess

Question

I have a subfolder in which I am running a wsgi app. I also have an addon domain pointing to this subfolder. I have trouble setting up the .htaccess file in the subfolder.
My current file structure:
public_html/
.htaccess
irrelevant index.html
some other irrelevant stuff
sub_folder/
.htaccess
app.wsgi
I have a maindomain.com pointing to /public_html/, and an addondomain.com pointing to /sub_folder/.
Currently the .htaccess file in the root folder is empty, the one in sub_folder is:
RewriteEngine On
RewriteBase /
RewriteRule ^(app\.wsgi/.*)$ - [L]
RewriteRule ^(.*)$ app.wsgi/$1 [QSA,L]
This works if I go to addondomain.com, but gives me a 404 when I go to maindomain.com/sub_folder. The log shows that it looks for /public_html/app.wsgi then, instead of /public_html/sub_folder/app.wsgi. How can I rewrite the .htaccess to make it work in both scenarios?

Answer 1

This should work with add-on domain as well.
RewriteEngine On
RewriteBase /
RewriteRule ^(app\.wsgi/.*)$ - [L]
RewriteCond %{HTTP_HOST} ^maindomain.com$ [NC]
RewriteRule ^sub_folder/(.*)$ sub_folder/app.wsgi/$1 [NC,QSA,L]
RewriteCond %{HTTP_HOST} ^addondomain.com$ [NC]
RewriteRule ^(sub_folder/)?(.*)$ app.wsgi/$1 [NC,QSA,L]
EDIT :
The rules above need to be tweaked since OP's .htaccess is already within /sub_folder. The ones above would still work if anyone wants their root /.htaccess to be in the driving seat.
RewriteEngine On
RewriteBase /
RewriteRule ^(app\.wsgi/.*)$ - [L]
RewriteCond %{HTTP_HOST} ^maindomain.com$ [NC]
RewriteRule ^(.*)$ sub_folder/app.wsgi/$1 [NC,QSA,L]
RewriteCond %{HTTP_HOST} ^addondomain.com$ [NC]
RewriteRule ^(.*)$ app.wsgi/$1 [NC,QSA,L]

Answer 2

I made it work, sort of...
RewriteEngine On
RewriteBase /
RewriteRule ^(app\.wsgi/.*)$ - [L]
RewriteCond %{REQUEST_URI} ^/sub_folder [NC]
RewriteRule ^(.*)$ sub_folder/app.wsgi/$1 [QSA,L]
RewriteCond %{REQUEST_URI} !^/sub_folder[NC]
RewriteRule ^(.*)$ app.wsgi/$1 [QSA,L]
#Ravi's answer works with addondomain.com, but not with maindomain.com/sub_folder, because in that case the index is showed, because it is not redirected to app.wsgi.
To solve this, I added a second RewriteCond and RewriteRule. The problem now is, it doesn't work when you go to addondomain.com/sub_folder (although that shouldn't happen). So if there is a better answer that also handles that properly, please enlighten me. Otherwise I'll just hope that that situation doesn't happen.
Edit:
This works:
RewriteEngine On
RewriteBase /
RewriteRule ^(app\.wsgi/.*)$ - [L]
RewriteCond %{HTTP_HOST} ^maindomain.com$ [NC]
RewriteRule ^(.*)$ sub_folder/app.wsgi/$1 [NC,QSA,L]
RewriteCond %{HTTP_HOST} ^addondomain.com$ [NC]
RewriteRule ^(.*)$ app.wsgi/$1 [NC,QSA,L]
Ravi's exact code didn't work, because this .htaccess is in the sub_folder, so the ^(.*)$ part is only the stuff after sub_folder/, somehow. But modified like this it works. Thanks for the help.