Activation fails in 1.8.9 due to a code error

[yetanotherse]

Describe the bug
On trying to activate the plugin, you get the following error.

Plugin could not be activated because it triggered a fatal error.

Fatal error: Uncaught Error: Call to a member function query() on null in /nas/content/staging/xxx/wp-content/plugins/object-sync-for-salesforce/classes/activate.php:143 Stack trace: #0 [internal function]: Object_Sync_Sf_Activate->wordpress_salesforce_tables('') #1 /nas/content/staging/xxx/wp-includes/class-wp-hook.php(286): call_user_func_array(Array, Array) #2 /nas/content/staging/xxx/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #3 /nas/content/staging/xxx/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #4 /nas/content/staging/xxx/wp-admin/plugins.php(180): do_action('activate_object...') #5 {main} thrown in /nas/content/staging/xxx/wp-content/plugins/object-sync-for-salesforce/classes/activate.php on line 143

To Reproduce
Steps to reproduce the behavior:

1. Install 1.8.9 version of Object Sync in WP
2. Click on activate plugin

Expected behavior
Plugin should get activated

Environment (please complete the following information):

• WordPress Version: 4.9.8
• PHP Version: 7.2.20

Solution
Found that the reference to wpdb is being used without this in activate.php on like 143 and 144 which was causing the issue. Replacing $wpdb with $this->wpdb fixes the issue.

Will create a pull request for the same.

[jonathanstegall]

@yetanotherse I'll do some testing on this today. I've seen some folks report this issue but I haven't been able to reproduce it, so I can't tell what environment is causing/preventing it.

If I can't reproduce it, i'll test your PR and make sure it doesn't cause any issues, and I'll approve it if it doesn't.

[yetanotherse]

@jonathanstegall Sounds good, thanks. Here is my environment.

WordPress 4.9.8
PHP 7.2.20-2+ubuntu18.04.1+deb.sury.org+1
Apache
MySQL 5.7.26

Having said that, I guess the issue should be reproducible on any system when trying to activate the plugin since the execution context for $wpdb is incorrect.

[jonathanstegall]

@yetanotherse you're right that it's incorrect. I'm not sure why it doesn't always have an error for that. Maybe many configs are more forgiving. In any case I'll accept the fix.