[lloeki]

There is. CRuby code gets compiled to ISeq (VM bytecode) upon `load` / `require` / `eval`. JRuby does similar things (IIRC using InvokeDynamic).

The difference (and that does not even need to involve Rails) is that these three - and thus compilation - happen at runtime, anytime, always.

The fact that a typical "main" file follows the "require first, then define modules and classes, then execute" creates a mental illusion of order; the fact that generally dependencies also follow this propagates that illusion across the board.

Therefore at the ruby source level you can only have runtime checks (and failure via exceptions), unless you bring in another static analysis tool such as Sorbet or RBS+Steep, which is an actual solution to enforce interface contracts without risking blowing up an app at runtime. That stays true even if there were a hypothetical "abstract" Ruby-level keyword. The only other solution without such tools is to have perfect (runtime) coverage via tests.

Note that mruby takes a fundamentally different approach here, and there's no require nor load.

[byroot]

> thus compilation - happen at runtime, anytime, always.

To be a bit pedantic, you can compile Ruby code with `RubyVM::InstructionSequence.compile`, and then dump and load it as a String.

That's one of the things Bootsnap does to speedup boot time. And when you do that, there's no compilation at runtime.

But that doesn't change anything about OP's suggestion, it's still impossible to know if an interface will ever be implemented.

https://docs.ruby-lang.org/en/3.3/RubyVM/InstructionSequence...

[lloeki]

Indeed, I did not mention Bootsnap so as to detract the core point.

> That's one of the things Bootsnap does to speedup boot time. And when you do that, there's no compilation at runtime.

Correct, if one does `bootsnap precompile`.

Bootsnap hooks itself on `Kernel#load` + `Kernel#require` and `RubyVM::InstructionSequence#load_iseq`:

https://github.com/Shopify/bootsnap/blob/f627992c52642394311...

https://github.com/Shopify/bootsnap/blob/f627992c52642394311...

https://github.com/Shopify/bootsnap/blob/f627992c52642394311...

https://github.com/Shopify/bootsnap/blob/f627992c52642394311...

Essentially this means that it makes LOAD_PATH lookup faster + intercepts iseq compilation to store to cache on a miss and return a cached version on a hit.

That does not change the load order.

> But that doesn't change anything about OP's suggestion, it's still impossible to know if an interface will ever be implemented.

Again correct, as even with `bootsnap precompile` it would only result in earlier ISeq generation (it is essentially cache priming instead of doing it "lazily" on demand), not the time at which these ISeq get loaded and effective, so even then an `abstract` keyword would be ineffective (or rather, equivalent to raising NotImplementedError, i.e syntactic sugar)

The only way to do it outside of runtime is with type information, ensuring that only certain types respecting a contract reach the point where the expected interface is made use of. I'm using RBS+Steep, not just for that but this is one of the main reasons and I can attest it does work very well in practice: when the types don't respect the contract it blows up as expected, at which stage raising exceptions is either redundant or a defensive coding mechanism (and I've actually had Steep yell at me because some clauses were unreachable due to types ensuring the contract)

[rezonant]

Completely correct. I should have said there is no compilation step for the developer to be more clear.