Adopt modern Active Record patterns

[shmax]

Description

This is a first pass at aligning more closely with modern Active Record, based on this PR by @ipundit

The broad strokes are that you can now chain relational commands together:

$book = Book::where(['title = ?", "Green Eggs and Ham"])->order("title")->first();
$books = Book::first([1,2,3]);
$books = Book::all()->to_a();
$book = Book::select('name')->find(1);
$book = Book::take();

There are a number of major breaking API changes. Briefly:

• find_all_by_... -style magic methods have been removed.
• find no longer takes an options array. The only valid arguments now are primary keys, or arrays of primary keys ("first" and "last" arguments are also no longer supported).
• count_by_...-style magic methods have been removed.

Other changes:

• renamed Expression to WhereClause
• Did a pass at setting up Generics (via PHPStan), so Relation can properly return whatever subclass of Model it is working with. Same for Table.
• Encoded rules for dynamic return types (ie first, last, find) into PHPStan extensions.

TODO

• Relation needs to implement iterable, so we can use it with foreach
• need to flesh out select, include, group, etc
• need to do another pass on documentation
• not sure if there are or will be any methods that allow a user to type out a big options object, eg:

    $res = Book::everything([
     "order" => "title,
     "limit" => 4,
     "conditions" => [
      "title" => "Walden"
     ]
    ]).to_array();

Is that a thing? If it is, I'll need to be careful about how I'm handling "conditions" (internally, I push instances of WhereClause).

[ipundit]

I've done a quick review of this large PR. Good job! That was a lot of work. A spec issue that comes to mind is when clauses are repeated. Should:

Author::select('A')->select('B')->find

select only B (this is what currently happens), throw an error, or select columns A and B?

But repeated where clauses act differently:

Author::where('A')->where('B')->find

it does where('A and B'). But why the inconsistency with select which replaces A with B? This should be specified in the documentation.

A similar reasoning and documentation exercise would have to be done for having, group, include, from, and all the other $VALID_OPTIONs that we have.

[ipundit]

I think that we should also put into the readme.md file that the goal of this project is to implement Ruby on Rails version v as faithfully as possible with exceptions a, b, c, d, etc... What is v? I think it's version 4, but am unsure. It depends how far you want to go before releasing this time around.

[shmax]

select only B (this is what currently happens), throw an error, or select columns A and B?

Great question. I checked out Rails in the debugger, and it definitely collects multiple select statements, and also supports arrays of field names, so I made the same change, here: aaf8c0d

We should probably also support doing variadic lists, like:

Book::select("name", "publisher)->take();

But let's revisit that kind of thing in a future PR.

[shmax]

A similar reasoning and documentation exercise would have to be done for having, group, include, from, and all the other $VALID_OPTIONs that we have.

If you're ready to get back to coding, it would be great if you could help out with that effort. I think most of our implementations of these features are a bit undercooked, and I just don't have the energy to go through them all right now.

[shmax]

Implemented Relation::not: 8113e26

[shmax]

@ipundit Thank you so much for all the great review comments.

I know you still have a few ideas about how to do things, but rather than circle around this PR forever I went ahead and merged it so you can resume making your own direct contributions.

There are a number of TODO items:

• revisit some of the new chaining methods (select, include, limit, group, etc), make them a bit more robust and inline with RoR, and improve documentation
• continue work on tests (I think the DatabaseTest ones are broken, in that setUp doesn't seem to do anything)
• implement iterator support for Relation (I'm working on that one now)
• start testing this out in real world code (maybe draft an RC release?)

Or whatever you like. Thanks again.