split cases for different injectors

[SlayerBirden]

Method getConfigFile is not defined in the InjectorInterface hence it's missing from some injectors.
Adjusted logic to apply different "get" logic based on different injector types with default fallback.

This fixes #39

[weierophinney]

A few comments:

• Please add a @todo annotation to the InjectorInterface to add a getConfigFile() method in the next major version.
• Add a @todo annotation to getInjectorConfigFileName() to remove it for the next major version in favor of the defined getConfigFile() method on the interface.
• Please add unit tests so we can validate the fix.

Thanks!

[weierophinney]

Please split each of these cases into its own method, and return the results of calling that method.

As an example:

private function getInjectorConfigFileName(InjectorInterface $injector)
{
    if ($injector instanceof ConfigInjectorChain) {
        return $this->getConfigFileNameFromInjectorChain($injector);
    }
    // etc.
    return '';
}

private function getConfigFileNameFromInjectorChain(ConfigInjectorChain $injector)
{
    $names = [];
    foreach ($injector->getCollection() as $item) {
        $names[] = $this->getInjectorConfigFileName($item);
    }
    return implode(', ', $names);
}

[SlayerBirden]

@weierophinney done; removed the noop case as it's not actually possible to reach it with current ConfigDiscovery logic

[SlayerBirden]

okulik@okulik:~/Sites/projects/zend-component-installer$ ./vendor/bin/phpunit --filter testUninstallMessageWithDifferentInjectors
PHPUnit 6.4.3 by Sebastian Bergmann and contributors.

..                                                                  2 / 2 (100%)

Time: 203 ms, Memory: 8.00MB

OK (2 tests, 4 assertions)

@weierophinney ^ test results

[weierophinney]

Thanks, @SlayerBirden