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symfony/src/Symfony/Component/DependencyInjection/ChildDefinition.php

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<?php
/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <fabien@symfony.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Symfony\Component\DependencyInjection;
Not allowing autoconfigure, instanceofConditionals or defaults for ChildDefinition Also, not allowing arguments or method calls for autoconfigure. This is a safety mechanism, since we don't have merging logic. It will allow us to add this in the future if we want to. The reason is that parent-child definitions are a different mechanism for "inheritance" than instanceofConditionas and defaults... creating some edge cases when trying to figure out which settings "win". For example: Suppose a child and parent definitions are defined in different YAML files. The child receives public: false from its _defaults, and the parent receives public: true from its _defaults. Should the final child definition be public: true (so the parent overrides the child, even though it only came from _defaults) or public: false (where the child wins... even though it was only set from its _defaults). Or, if the parent is explicitly set to public: true, should that override the public: false of the child (which it got from its _defaults)? On one hand, the parent is being explicitly set. On the other hand, the child is explicitly in a file settings _defaults public to false. There's no correct answer. There are also problems with instanceof. The importance goes: defaults < instanceof < service definition But how does parent-child relationships fit into that? If a child has public: false from an _instanceof, but the parent explicitly sets public: true, which wins? Should we assume the parent definition wins because it's explicitly set? Or would the _instanceof win, because that's being explicitly applied to the child definition's class by an _instanceof that lives in the same file as that class (whereas the parent definition may live in a different file). Because of this, @nicolas-grekas and I (we also talked a bit to Fabien) decided that the complexity was growing too much. The solution is to not allow any of these new feature to be used by ChildDefinition objects. In other words, when you want some sort of "inheritance" for your service, you should *either* giving your service a parent *or* using defaults and instanceof. And instead of silently not applying defaults and instanceof to child definitions, I think it's better to scream that it's not supported.
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use Symfony\Component\DependencyInjection\Exception\BadMethodCallException;
use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
use Symfony\Component\DependencyInjection\Exception\OutOfBoundsException;
/**
* This definition extends another definition.
*
* @author Johannes M. Schmitt <schmittjoh@gmail.com>
*/
class ChildDefinition extends Definition
{
private $parent;
/**
* @param string $parent The id of Definition instance to decorate
*/
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public function __construct(string $parent)
{
$this->parent = $parent;
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$this->setPrivate(false);
}
/**
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* Returns the Definition to inherit from.
*
* @return string
*/
public function getParent()
{
return $this->parent;
}
/**
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* Sets the Definition to inherit from.
*
* @param string $parent
*
* @return $this
*/
public function setParent($parent)
{
$this->parent = $parent;
return $this;
}
/**
* Gets an argument to pass to the service constructor/factory method.
*
* If replaceArgument() has been used to replace an argument, this method
* will return the replacement value.
*
* @param int|string $index
*
* @return mixed The argument value
*
* @throws OutOfBoundsException When the argument does not exist
*/
public function getArgument($index)
{
if (\array_key_exists('index_'.$index, $this->arguments)) {
return $this->arguments['index_'.$index];
}
return parent::getArgument($index);
}
/**
* You should always use this method when overwriting existing arguments
* of the parent definition.
*
* If you directly call setArguments() keep in mind that you must follow
* certain conventions when you want to overwrite the arguments of the
* parent definition, otherwise your arguments will only be appended.
*
* @param int|string $index
* @param mixed $value
*
* @return self the current instance
*
* @throws InvalidArgumentException when $index isn't an integer
*/
public function replaceArgument($index, $value)
{
if (\is_int($index)) {
$this->arguments['index_'.$index] = $value;
} elseif (0 === strpos($index, '$')) {
$this->arguments[$index] = $value;
} else {
throw new InvalidArgumentException('The argument must be an existing index or the name of a constructor\'s parameter.');
}
return $this;
}
Not allowing autoconfigure, instanceofConditionals or defaults for ChildDefinition Also, not allowing arguments or method calls for autoconfigure. This is a safety mechanism, since we don't have merging logic. It will allow us to add this in the future if we want to. The reason is that parent-child definitions are a different mechanism for "inheritance" than instanceofConditionas and defaults... creating some edge cases when trying to figure out which settings "win". For example: Suppose a child and parent definitions are defined in different YAML files. The child receives public: false from its _defaults, and the parent receives public: true from its _defaults. Should the final child definition be public: true (so the parent overrides the child, even though it only came from _defaults) or public: false (where the child wins... even though it was only set from its _defaults). Or, if the parent is explicitly set to public: true, should that override the public: false of the child (which it got from its _defaults)? On one hand, the parent is being explicitly set. On the other hand, the child is explicitly in a file settings _defaults public to false. There's no correct answer. There are also problems with instanceof. The importance goes: defaults < instanceof < service definition But how does parent-child relationships fit into that? If a child has public: false from an _instanceof, but the parent explicitly sets public: true, which wins? Should we assume the parent definition wins because it's explicitly set? Or would the _instanceof win, because that's being explicitly applied to the child definition's class by an _instanceof that lives in the same file as that class (whereas the parent definition may live in a different file). Because of this, @nicolas-grekas and I (we also talked a bit to Fabien) decided that the complexity was growing too much. The solution is to not allow any of these new feature to be used by ChildDefinition objects. In other words, when you want some sort of "inheritance" for your service, you should *either* giving your service a parent *or* using defaults and instanceof. And instead of silently not applying defaults and instanceof to child definitions, I think it's better to scream that it's not supported.
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/**
* @internal
*/
public function setAutoconfigured($autoconfigured)
{
throw new BadMethodCallException('A ChildDefinition cannot be autoconfigured.');
}
/**
* @internal
*/
public function setInstanceofConditionals(array $instanceof)
{
throw new BadMethodCallException('A ChildDefinition cannot have instanceof conditionals set on it.');
}
}