Custom tree walkers are not allowed to add new components to the query

Ok this is much more complicated to allow then i thought. The problem is that the QueryComponents are passed by value, as an array, not by reference. That prevents changing them because this change wouldn't be visible in the output walker.

I can add a method to allow this in the OutputWalker for now, but generally this requires a bigger refactoring on the Query Components.

Added setQueryComponent() in SQL Walker to allow modification in output walker.

I'm afraid that this doesn't solve the initial problem at all. I'll try to describe it in more details to show what I mean. Suppose we have two doctrine extensions each of which contain its own tree walker. Each of these tree walkers need to modify AST and add new component to it (joined with some component already existing in the query). The first problem is that each tree walker has its own queryComponents array which is not passed between them, although they not necessary need to use queryComponents - they could use only AST. The second, bigger problem is that the Parser class does not know anything about modifications of queryComponents in tree walkers and cannot pass modified version to the OutputWalker. The goal of submitting this issue was to allow adding new components to the query in tree walkers which is not achievable by your fix. I think it may be the first step in the right direction. Maybe TreeWalkerAdapter should have public method getQueryComponents() which would be used by the Parser to pass modified queryComponents between different tree walkers and finally to the OutputWalker ? This would not break backward compatibility and solve this issue. What do you think about it?

I've tried to implement the solution mentioned in previous comment but it's also not so clean and easy as I thought. Each tree walker (including TreeWalkerChain) would have to implement getQueryComponents() and setQueryComponent($alias, array $component) methods. The same with SqlWalker, so the TreeWalker interface should have these methods, which would break BC in some way (walkers that do not inherit from SqlWalker or TreeWalkerAdapter will fail to compile). So maybe my first solution (PR #464) is not so bad for now? In the future queryComponents could be replaced by a special object or could be passed by a reference to allow modifications.

Marked as improvement as its not a bug.

A solution might probably implement an object holding all the QueryComponent, implementing ArrayAccess. So that way the state can be shared.

Just hit this while developing an ast walker... Will look into it too since I need it more than soon.

As a VERY UGLY workaround, I used a static variable and a custom sql walker in combination with my AST walker.

namespace Comcom\Versioning\ORM\Query;


use Doctrine\ORM\Query\SqlWalker;

class WorkaroundSqlWalker extends SqlWalker
{
    public function __construct($query, $parserResult, array $queryComponents)
    {
        parent::__construct($query, $parserResult, $queryComponents);

        foreach (VersionWalker::$additionalAliases as $alias => $value) {
            $this->setQueryComponent($alias, $value);
        }
    }
}