Try hard-refreshing this page to fix the error.

Wellwisher

I am attempting to create an "identical instance" of my 'live production' forum on another domain name for testing purposes.

I want to be able to test extensions and Flarum updates in a safe enviroment before I run them on my live production site.

I copied over all the Flarum files & folders, together with the database from my live production site.
I am now in the process of connecting the two together on another domain name.

I am at the stage where I get this error:

Something went wrong while trying to load the full version of this site. Try hard-refreshing this page to fix the error.

I've set the debugger to "True" and this is the message I am getting:

Flarum information

TypeError
Return value of Flarum\Frontend\Compiler\Source\StringSource::getContent() must be of the type string, null returned

Config file:

<?php return array (
'debug' => false,
'database' =>
array (
'driver' => 'mysql',
'host' => 'mysql.new-domain-name.com',
'port' => XXXX,
'database' => 'database',
'username' => 'username',
'password' => 'password',
'charset' => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',
'prefix' => '',
'strict' => false,
'engine' => NULL,
'prefix_indexes' => true,
),
'url' => 'https://www.new-domain-name.com/discuss',
'paths' =>
array (
'api' => 'api',
'admin' => 'admin',
),
'headers' =>
array (
'poweredByHeader' => true,
'referrerPolicy' => 'same-origin',
),
);

Console error:

luceos

These could be a few things.. StringSource tries to pull in some less into a compiler. You might not have copied all files, best is to not copy the vendor file, but run composer install anew on your other server.

Wellwisher

luceos thanks I will try this. I think this is what Clark recommended too here.

I am going to try copying every file & folder expect vendor and run composer to install a new instance. Then dropping the new database and importing my own.

I thought it was worth trying to copy everything exactly "as is" on my live forum to see if that works.
However it is not the case for some reason.

Wellwisher

So here's how I solved the issue:

Please note, this works for my VPS hosting provider dreamhost.com.

Delete the vendor folder (as suggested by luceos and clarkwinkelmann)
Install composer again (I renamed my old composer file to "original_composer.phar" and then installed composer again)
Run terminal code: "php composer.phar update"
Run terminal code: "php flarum cache:clear" and this is what does the trick! It got rid of the error message "Something went wrong while trying to load the full version of this site. Try hard-refreshing this page to fix the error."
However, my forum was blank, I could see the login page, logo, nav bar etc, but no posts were showing below. To fix this, I signed into the admin panel and disabled all the extensions and then re-enabled them and then my posts began showing. 🥰

I think, looking back, just clearing the cache may have worked to resolve the initial error message. With that said, I feel deleting vendor and installing composer is the best way of doing it.