NEW: Extension points for FilesystemPublisher.

[mfendeksilverstripe]

NEW: Extension points for FilesystemPublisher.

• Extension points added to generatePageResponse() to allow better extensibility

[dhensby]

The idea behind the publisher classes is that developers can easily implement their own and add their own logic easily. There shouldn't really be a need for extension hooks with the current implementation.

What is the scenario where this is needed?

[mfendeksilverstripe]

@dhensby My team found useful to have the ability to inject some custom behaviour via these extension points. For example we have in-memory cache which needs to be flushed after each call of generatePageResponse(). It's not something that warrants the implementation of a new file system publisher as we're not altering any core behaviour but instead a simple extension can accomodate this requirement.

Also, we found useful to reset some core states such as controller stack something like this:

try {
    $controllers = [];

    // pop all current application's controllers to simulate cold boot
    while (Controller::has_curr()) {
        $controller = Controller::curr();
        $controllers[]= $controller;
        $controller->popCurrent();
    }

    return parent::generatePageResponse($url);
} finally {
    // flush all in-memory cached data

    foreach (array_reverse($controllers) as $controller) {
        // reapply previous controllers
        $controller->pushCurrent();
    }
}

[GuySartorelli]

Your use case seems sensible to me. Please retarget this PR to the 6 branch and remove the unrelated changes.

[mfendeksilverstripe]

I've pushed up changes as per your request @GuySartorelli , please review.

[GuySartorelli]

You swapped the target branch after resetting commits, which means the new CI isn't able to run. Can you please force push so that the CI runs correctly?

[mfendeksilverstripe]

Done @GuySartorelli

[GuySartorelli]

Changes look good to me, will merge when CI goes green.