feat: rename namespaces and provide aliases

[bshaffer]

Addresses #692:

• Adds namespaces, removes underscores
• Adds autoloading for namespaces
• Flattens directories for PSR-4

Backwards-compatibility concerns

BC is preserved using aliases.php. This loads the (minimal) 20 classes in this library upfront and creates aliases for them.

Another option is to define a custom autoload.php which lazy-loads the Google_ classes as they're requested:

// src/autoload.php
$classMap = [
    'Google_Client' => 'Google\Client',
    // ...
];

spl_autoload_register(function ($class) use ($classMap) {
    if (isset($classMap[$class])) {
        class_alias($classMap[$class], $class);
        return true;
    }
});

The problem with this is the autoload.php function is invoked on every class-exists. Which is preferred? Tell me your thoughts in the comment section and don't forget to smash that "subscribe" button!

Note: this is independent of google/apiclient-services

[jdpedrie]

I'm worried about this map falling out of date if we add new classes. Would be nice to test that all the classes in the src folder within the Google\\ namespace have a mapping. Some combination of RecursiveDirectoryIterator and FileReflector maybe.

Also, maybe just my preference, but I'd reverse the keys and values of this array. Makes more sense to me that the real name is the key, and also corresponds better to the argument order of class_alias().

[mfn]

I'm worried about this map falling out of date if we add new classes

Stupid outsider question (apologies if this isn't appropriate here!): why would a new class still be relevant for the old non-namespaced version? Would this still be maintained in parallel … 🤔

Thanks!

[jdpedrie]

That's a good point, I suppose it's something that we'd need to consider. It would seem strange to have some classes without aliases, but maybe that's good, might be a nudge towards upgrading to use the namespace.

[bshaffer]

I switched the order of aliases.php

I agree with @mfn that there'd be no reason to add an alias for a new class

[jdpedrie]

I think I have a small preference for the aliases.php file over an autoloader, but it may be because it already exists.

[bshaffer]

@jdpedrie I think it makes things easier and simpler to autoload aliases.php up front than to mess with an autoloader. The number of classes is small enough that it's unlikely to have a noticeable impact.