DDC-3054: [GH-991] Ability to define custom functions with callback instead of class name

[doctrinebot]

Jira issue originally created by user @doctrinebot:

This issue is created automatically through a Github pull request on behalf of mnapoli:

Url: #991

Message:

Right now the only way to define custom DQL functions is by giving the class name, and Doctrine will create the class:

$config->addCustomNumericFunction('FOO', 'My\Custom\DqlFunction');

This is very limiting when the custom functions has dependencies, for example it can't be created by a DI container.

The approach I have taken here is very simple: it allows to define a callback instead of the class name: the callback will be called and it should return the instance:

$config->addCustomNumericFunction('FOO', function($funcName) {
    return new My\Custom\DqlFunction($funcName);
});

On a side note, I think it would be great to generalize that approach because currently there are a lot of places where the same constraints apply.

[doctrinebot]

Comment created by @doctrinebot:

A related Github Pull-Request [GH-991] was closed:
#991

[doctrinebot]

Issue was closed with resolution "Fixed"