Semantic: change behaviour of `mix`, `js` and `attrs` modes

[miripiruni]

.mix()('b') should set b as mix. Last call of mix() set new value which is not extended previous. .addMix()('newMix') should extend value of previous mix value.

The same for js() and attrs().

Also, I think we need addContent() mode to avoid applyNext() copypaste in chain of the same mode templates.

BTW, see https://gist.github.com/miripiruni/7561cc8ad56d0d4d5184

[tadatuta]

Please refer to old issues https://github.com/bem/bem-xjst/issues/242 (based on https://github.com/bem/bem-core/issues/820)

[tadatuta]

Discussed there's an issue with possibility to dismiss addMix() declared on previous level.

[qfox]

I think we need addContent() mode to avoid applyNext()

I don't see what we get with avoiding applyNext() calls. addContent, addMix, addAnythingElse won't make API easier. Compare:

block('a').addMix()(() => {elem: 'e'});
// vs
block('a').mix()(() => applyNext().concat({elem: 'e'}));

// and
block('a').addContent()(() => {elem: 'e', content: 'qwe'});
// vs
block('a').content()(() => applyNext().concat({elem: 'e', content: 'qwe'}));

Worth?

[miripiruni]

@zxqfox Incorrect example. Look: block('a').mix()(() => applyNext().concat({elem: 'e'})); will fall if applyNext() return not an Array. First of all you need to check type.

With addMix/addAttrs/etc we’ll get expressiveness and brevity. The correct compare:

block('page').addMix()(() => 'mixed');
// vs
block('page').mix()(function() {
    var mixes = applyNext();
    if (!Array.isArray(mixes)) mixes = [ mixes ];
    return mixes.concat('mixed');
});

[qfox]

Ok, but let's do mix an array. It's much easier and cleaner, isn't it?

[miripiruni]

@zxqfox OK, but where you would like to change it?

[miripiruni]

@zxqfox я процитирую себя самого:

если мы хотим сформировать выход (часть выходного дерева) то нужно использовать режимы. То есть вся «запись» должна происходить в них. А чтение, с целью проверить что-либо, нужно производить в нормализованных значениях.

proof

[qfox]

Ну так давай нормализовывать this.mix, равно как мы это делаем с this.mods? Аналогично this.js, this.attrs

[miripiruni]

@zxqfox the only reason why we change this.mods/this.elemMods now is that we don’t have any other way to do it in current version. We need change it. We need more explicit way to make output not by side effects but in «clear declarative functions» way.

Compare:

block('a').def()(function() {
    this.mix.push('mixed');
    return applyNext();
});
// vs
block('a').addMix()('mixed'); // Much more explicitly than def() with side effect.

[qfox]

Т.е. в будущем мы не будем нормализовывать mods, elemMods? Я не понял аргументации ПРОТИВ нормализации mix, js, attrs.

[miripiruni]

@zxqfox я против записи в this.*, но не против нормализации.

[qfox]

@miripiruni Я против записи в ctx ;-)

[miripiruni]

https://github.com/bem/bem-xjst/releases/tag/v8.0.0