SMWSearch: Fix unit test; Move access to MediaWikiServices to ApplicationFactory

[s7eph4n]

This PR is made in reference to:

• Work around deprecated/removed DatabaseBase::getSearchEngine #1897 (comment)
• Work around deprecated/removed DatabaseBase::getSearchEngine #1897 (review)

This PR addresses or contains:

• fix SearchTest::testGetDefaultFallbackSearchEngineForNullFallbackSearchType
• remove direct accesses to MediaWikiServices from Search.php
• add ApplicationFactory::getMediaWikiServices
• add $callbackLoader->registerCallback( 'MediaWikiServices', ...) to SharedCallbackContainer
  (not sure if that is the correct thing to do)

This PR includes:

• Tests (unit/integration)
• CI build passed

[mwjames]

I would have thought you make this available to the ApplicationFactory as dedicated service hiding MediaWikiServices as much we can to avoid issues when things change again on the MW side.

The DI container would always return a DBLoadBalancer instance ( avoiding the null case) and internally makes the call to either MediaWikiServices or LBFactory but it is hidden from the consumer who calls ApplicationFactory::getMediaWikiDbLoadBalancer.

[s7eph4n]

Ok, no problem.

What about getDefaultSearchEngineTypeForDB?
Not sure if I should register a callback or just add the method to ApplicationFactory as is.

[mwjames]

Well, assuming that we want to ban MediaWikiServices access directly and given that we already have a reference in the DI container, I'd say just register a service and call it in ApplicationFactory.

PS: For the curious mind, during testing all objects that are available via the DI container can be overridden from the outside (because sometimes you cannot control the injection) such as:

use SMW\Tests\TestEnvironment

private $testEnvironment;

protected function setUp() {
    parent::setUp();

    $store = $this->getMockBuilder( '\SMW\Store' )
        ->disableOriginalConstructor()
        ->getMockForAbstractClass();

    $this->testEnvironment= new TestEnvironment();
    $this->testEnvironment->registerObject( 'Store', $store );

    // Example

    // Reset the Title/TitleParser otherwise a singleton instance holds an outdated
    // content language reference
    $this->testEnvironment->resetMediaWikiService( '_MediaWikiTitleCodec' );
    $this->testEnvironment->resetMediaWikiService( 'TitleParser' );
}

protected function tearDown() {
    $this->testEnvironment->tearDown();
    parent::tearDown();
}

[mwjames]

PS: I'll be back in a week, in case something is unclear don't get frustrated, I'll try to catch up as soon as possible.

[mwjames]

This doesn't seems to be an issue on 1.27+ [0] but all others return with a:

1) SMW\Tests\MediaWiki\Search\SearchTest::testGetDefaultFallbackSearchEngineForNullFallbackSearchType
RuntimeException: SearchEngine is not a valid fallback search engine type.

[0] https://travis-ci.org/SemanticMediaWiki/SemanticMediaWiki/builds/166264508

[mwjames]

Expecting this to fix #1916.

[s7eph4n]

This is becoming a nightmare. Could have sworn I've run the tests. Oh well...

[mwjames]

Thanks.