Make Expression into an interface

[dakujem]

Make Expression into an interface

[milo]

I don't think that expression should be an interface as is. Expression represents Dibi specific syntax. If so, an interface should say that object can be converted into Dibi Expression e.g. via method function toDibiExpression(): Expression.

[dakujem]

I don't see how that is different. Your object would have to return an instance of "dibi specific syntax" anyway and it would achieve the same. But I would be comfortable with that too, anything is better than inheriting from internal objects, that tend to become final, private and such...

[dg]

Why do you specifically need it?

[dakujem]

I'm writing a convertor that converts key-value arrays to conditions, agnostic of the storage backend.

For SQL, I'm trying to use Dibi. One of the objects I internally use is a "self-unpackable" condition used on both Fluent like this $expression($fluent) as a decorator, and in "regular sql" with %ex modifier.

With Dibi as it is, I need to either extend Expression or use a workaround to support both, neither being an elegant solution.

[dg]

And why can't the converter create a Dibi\Expression object?

[dakujem]

At the time of writing, I had a syntax tree composed of backend-agnostic nodes. I intended for these nodes to be instances of Expression, but I since scraped the idea and now use a tree traversal algo to converted the structure to a structure of nested Expressions. The downside of this is one more traversal.

This issue was meant to future-proof extensibility options with similar use cases, but I'm fine with the current state for now.