[8.x] DB command: Cope with missing driver parameters for mysql

[vroomfondle]

The problem

We don't expose our mysql installation via unix sockets (we only use network connections). Therefore our mysql config in config/database.php does not have a unix_socket entry.

This was causing the DB command to fail:

vagrant@dev:/var/www/api$ artisan db mysql 

In DbCommand.php line 138:
                                     
  Undefined array key "unix_socket"  
                                     

Discussion

As the unix socket is not necessarily required to connect to a mysql database, it seems sensible to ignore it if it's not present rather than throwing an error. The charset is also not required to connect.

Implementation

I have used the null coalescence operator to supply a blank string as default, which means getOptionalArguments() will filter it out and the socket/charset arguments won't be passed in the command string.

A similar change might be applicable for the other database drivers, but I do not have as much experience with them and don't have any instances to test against, so I have not changed those methods.

Testing

I've tested this locally against our mysql 8 installation and it works. I could not find any relevant unit tests to update but am happy to do so if somebody points me in the right direction.

[taylorotwell]

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