ngnix www to no-www on config file generated by certbot - nginx

Question

I am trying to get requests to example.com as well as www.example.com to go to https://example.com in the configuration file shown below. The file is exactly as generated by certbot.
Changing the two return 301 statements to
return 301 https://example.com$request_uri;
did not work as https://www.example.com still goes to https://www.example.com and not the desired https://example.com
Would appreciate if someone could point out the exact changes needed to get the desired result. Simplified instructions would be a bonus as I am quite new to both nginx and certbot. Thanks.
server {
root /var/www/html/drupal;
index index.php index.html index.htm;
server_name example.com www.example.com;
location / {
try_files $uri /index.php?$query_string;
}
location #rewrite {
rewrite ^/(.*)$ /index.php?q=$1;
}
location ~ [^/]\.php(/|$) {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
}
location ~ ^/sites/.*/files/styles/ {
try_files $uri #rewrite;
}
location ~ ^(/[a-z\-]+)?/system/files/ {
try_files $uri /index.php?$query_string;
}
listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server {
if ($host = www.example.com) {
return 301 https://$host$request_uri;
} # managed by Certbot
if ($host = example.com) {
return 301 https://$host$request_uri;
} # managed by Certbot
listen 80;
listen [::]:80;
server_name example.com www.example.com;
return 404; # managed by Certbot
}

Answer 1

Open the brackets for a clearer way.
Instead of one 443 listener, create 2. Same with the 80 ones.
Like that it's much easier for you to know what is doing what, one configuration for each pair of host and schema.
server {
listen 80;
listen [::]:80;
server_name www.example.com; #this will only listen to http://www.example.com
location / {
return 301 https://example.com$request_uri; #and will upgrade to https
}
#we don't want that many redirects, so this will go directly to example.com
}
server {
listen 80;
listen [::]:80;
server_name example.com; #this will only listen to http://example.com
location / {
return 301 https://$host$request_uri; #and will upgrade to https
}
}
server {
server_name www.example.com;
location / {
return 301 https://example.com$request_uri #this redirects to non-www
}
listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server{
#same server configuration as your first server bracket, only accepting https://example.com and not www.
}
I see that you are sending the arriving connection to a Drupal so think that the Drupal has a variable $base_url that any redirect that it makes it's made to that host, so if it's set to www.example.com, it won't matter you nginx conf, as Drupal itself can also make redirects.
Hope it helped, comment for any question.

Answer 2

Its working now, #flaixman. I made one change from your suggestion - which was to make just one block for 80, since they both did exactly the same thing. So, here's the final version : (I have hopefully not messed up something which might cause a problem later.)
server {
listen 80;
listen [::]:80;
server_name example.com www.example.com;
location / {
return 301 https://example.com$request_uri;
}
}
server {
server_name www.example.com;
location / {
return 301 https://example.com$request_uri;
}
listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server{
root /var/www/html/d8;
index index.php index.html index.htm;
server_name example.com;
location / {
try_files $uri /index.php?$query_string;
}
location #rewrite {
rewrite ^/(.*)$ /index.php?q=$1;
}
location ~ [^/]\.php(/|$) {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
}
location ~ ^/sites/.*/files/styles/ {
try_files $uri #rewrite;
}
location ~ ^(/[a-z\-]+)?/system/files/ {
try_files $uri /index.php?$query_string;
}
listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}