When WP_DEBUG is true show better errors for establishing database connection

[sivel]

Right now no matter if WP_DEBUG is enabled or not we always show some generic errors for Error establishing a database connection

We should display the specific error when WP_DEBUG is enabled.

[sivel]

Patch is just an idea of how we might do this. Open to other suggestions and patches.

[nacin]

I would tend to think we should not be exposing the output of mysql_error() on any site. Or, if we do, then we at least also check for display_errors/WP_DEBUG_DISPLAY, in case they want WP_DEBUG (as can be common in production) but are logging it.

[sivel]

The way that translations are handled for these errors makes it difficult to do conditionals like this. Mainly due to duplicating large portions of code and strings. Well maybe not large but more than I am comfortable with duplicating.

I may just need to stare at the code for a bit to get a creative solution, that is unless someone has recommendations.

[pento]

The strings have since been split up, making it much easier to insert a conditional string when WP_DEBUG and WP_DEBUG_DISPLAY are defined.

[Mte90]

check for WB_DEBUG and WP_DEBUG_DISPLAY

[Mte90]

I updated the patch but I am not sure about mysql_error because maybe wpdb have a wrapper for that but I am not an expert for this part.

[pento]

It would be best to put this in wpdb::bail(). That method will always be the one called when WPDB needs to kill page loading. There's no need to check WP_DEBUG && WP_DEBUG_DISPLAY here, as wpdb::$show_errors is set to that.

I would suggest appending it to $message at the start. Also, don't forget to check mysqli_error(). :-)

[Mte90]

new patch with in bail method

[SergeyBiryukov]

In 42716:

Database: If both WP_DEBUG and WP_DEBUG_DISPLAY are true, display a more specific error message in wpdb::bail().

Props sivel, Mte90, SergeyBiryukov.
Fixes #13657.